57ad033ce0
1265 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Andrii Nakryiko
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4bb7ea946a |
bpf: fix precision backtracking instruction iteration
Fix an edge case in __mark_chain_precision() which prematurely stops
backtracking instructions in a state if it happens that state's first
and last instruction indexes are the same. This situations doesn't
necessarily mean that there were no instructions simulated in a state,
but rather that we starting from the instruction, jumped around a bit,
and then ended up at the same instruction before checkpointing or
marking precision.
To distinguish between these two possible situations, we need to consult
jump history. If it's empty or contain a single record "bridging" parent
state and first instruction of processed state, then we indeed
backtracked all instructions in this state. But if history is not empty,
we are definitely not done yet.
Move this logic inside get_prev_insn_idx() to contain it more nicely.
Use -ENOENT return code to denote "we are out of instructions"
situation.
This bug was exposed by verifier_loop1.c's bounded_recursion subtest, once
the next fix in this patch set is applied.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Fixes:
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Andrii Nakryiko
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3feb263bb5 |
bpf: handle ldimm64 properly in check_cfg()
ldimm64 instructions are 16-byte long, and so have to be handled
appropriately in check_cfg(), just like the rest of BPF verifier does.
This has implications in three places:
- when determining next instruction for non-jump instructions;
- when determining next instruction for callback address ldimm64
instructions (in visit_func_call_insn());
- when checking for unreachable instructions, where second half of
ldimm64 is expected to be unreachable;
We take this also as an opportunity to report jump into the middle of
ldimm64. And adjust few test_verifier tests accordingly.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Reported-by: Hao Sun <sunhao.th@gmail.com>
Fixes:
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Dave Marchevsky
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1b12171533 |
bpf: Mark direct ld of stashed bpf_{rb,list}_node as non-owning ref
This patch enables the following pattern:
/* mapval contains a __kptr pointing to refcounted local kptr */
mapval = bpf_map_lookup_elem(&map, &idx);
if (!mapval || !mapval->some_kptr) { /* omitted */ }
p = bpf_refcount_acquire(&mapval->some_kptr);
Currently this doesn't work because bpf_refcount_acquire expects an
owning or non-owning ref. The verifier defines non-owning ref as a type:
PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF
while mapval->some_kptr is PTR_TO_BTF_ID | PTR_UNTRUSTED. It's possible
to do the refcount_acquire by first bpf_kptr_xchg'ing mapval->some_kptr
into a temp kptr, refcount_acquiring that, and xchg'ing back into
mapval, but this is unwieldy and shouldn't be necessary.
This patch modifies btf_ld_kptr_type such that user-allocated types are
marked MEM_ALLOC and if those types have a bpf_{rb,list}_node they're
marked NON_OWN_REF as well. Additionally, due to changes to
bpf_obj_drop_impl earlier in this series, rcu_protected_object now
returns true for all user-allocated types, resulting in
mapval->some_kptr being marked MEM_RCU.
After this patch's changes, mapval->some_kptr is now:
PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU
which results in it passing the non-owning ref test, and the motivating
example passing verification.
Future work will likely get rid of special non-owning ref lifetime logic
in the verifier, at which point we'll be able to delete the NON_OWN_REF
flag entirely.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20231107085639.3016113-6-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Shung-Hsi Yu
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82ce364c60 |
bpf: replace register_is_const() with is_reg_const()
The addition of is_reg_const() in commit 171de12646d2 ("bpf: generalize
is_branch_taken to handle all conditional jumps in one place") has made the
register_is_const() redundant. Give the former has more feature, plus the
fact the latter is only used in one place, replace register_is_const() with
is_reg_const(), and remove the definition of register_is_const.
This requires moving the definition of is_reg_const() further up. And since
the comment of reg_const_value() reference is_reg_const(), move it up as
well.
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231108140043.12282-1-shung-hsi.yu@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Song Liu
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045edee19d |
bpf: Introduce KF_ARG_PTR_TO_CONST_STR
Similar to ARG_PTR_TO_CONST_STR for BPF helpers, KF_ARG_PTR_TO_CONST_STR specifies kfunc args that point to const strings. Annotation "__str" is used to specify kfunc arg of type KF_ARG_PTR_TO_CONST_STR. Also, add documentation for the "__str" annotation. bpf_get_file_xattr() will be the first kfunc that uses this type. Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Vadim Fedorenko <vadim.fedorenko@linux.dev> Link: https://lore.kernel.org/bpf/20231107045725.2278852-4-song@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Song Liu
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0b51940729 |
bpf: Factor out helper check_reg_const_str()
ARG_PTR_TO_CONST_STR is used to specify constant string args for BPF helpers. The logic that verifies a reg is ARG_PTR_TO_CONST_STR is implemented in check_func_arg(). As we introduce kfuncs with constant string args, it is necessary to do the same check for kfuncs (in check_kfunc_args). Factor out the logic for ARG_PTR_TO_CONST_STR to a new check_reg_const_str() so that it can be reused. check_func_arg() ensures check_reg_const_str() is only called with reg of type PTR_TO_MAP_VALUE. Add a redundent type check in check_reg_const_str() to avoid misuse in the future. Other than this redundent check, there is no change in behavior. Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Vadim Fedorenko <vadim.fedorenko@linux.dev> Link: https://lore.kernel.org/bpf/20231107045725.2278852-3-song@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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4621202adc |
bpf: generalize reg_set_min_max() to handle two sets of two registers
Change reg_set_min_max() to take FALSE/TRUE sets of two registers each, instead of assuming that we are always comparing to a constant. For now we still assume that right-hand side registers are constants (and make sure that's the case by swapping src/dst regs, if necessary), but subsequent patches will remove this limitation. reg_set_min_max() is now called unconditionally for any register comparison, so that might include pointer vs pointer. This makes it consistent with is_branch_taken() generality. But we currently only support adjustments based on SCALAR vs SCALAR comparisons, so reg_set_min_max() has to guard itself againts pointers. Taking two by two registers allows to further unify and simplify check_cond_jmp_op() logic. We utilize fake register for BPF_K conditional jump case, just like with is_branch_taken() part. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-18-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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811476e9cc |
bpf: prepare reg_set_min_max for second set of registers
Similarly to is_branch_taken()-related refactorings, start preparing reg_set_min_max() to handle more generic case of two non-const registers. Start with renaming arguments to accommodate later addition of second register as an input argument. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-17-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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4d345887d2 |
bpf: unify 32-bit and 64-bit is_branch_taken logic
Combine 32-bit and 64-bit is_branch_taken logic for SCALAR_VALUE registers. It makes it easier to see parallels between two domains (32-bit and 64-bit), and makes subsequent refactoring more straightforward. No functional changes. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-16-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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b74c2a842b |
bpf: generalize is_branch_taken to handle all conditional jumps in one place
Make is_branch_taken() a single entry point for branch pruning decision making, handling both pointer vs pointer, pointer vs scalar, and scalar vs scalar cases in one place. This also nicely cleans up check_cond_jmp_op(). Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-15-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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c697289efe |
bpf: move is_branch_taken() down
Move is_branch_taken() slightly down. In subsequent patched we'll need both flip_opcode() and is_pkt_ptr_branch_taken() for is_branch_taken(), but instead of sprinkling forward declarations around, it makes more sense to move is_branch_taken() lower below is_pkt_ptr_branch_taken(), and also keep it closer to very tightly related reg_set_min_max(), as they are two critical parts of the same SCALAR range tracking logic. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-14-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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c31534267c |
bpf: generalize is_branch_taken() to work with two registers
While still assuming that second register is a constant, generalize is_branch_taken-related code to accept two registers instead of register plus explicit constant value. This also, as a side effect, allows to simplify check_cond_jmp_op() by unifying BPF_K case with BPF_X case, for which we use a fake register to represent BPF_K's imm constant as a register. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Link: https://lore.kernel.org/r/20231102033759.2541186-13-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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c2a3ab0946 |
bpf: rename is_branch_taken reg arguments to prepare for the second one
Just taking mundane refactoring bits out into a separate patch. No functional changes. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Link: https://lore.kernel.org/r/20231102033759.2541186-12-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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9e314f5d86 |
bpf: drop knowledge-losing __reg_combine_{32,64}_into_{64,32} logic
When performing 32-bit conditional operation operating on lower 32 bits
of a full 64-bit register, register full value isn't changed. We just
potentially gain new knowledge about that register's lower 32 bits.
Unfortunately, __reg_combine_{32,64}_into_{64,32} logic that
reg_set_min_max() performs as a last step, can lose information in some
cases due to __mark_reg64_unbounded() and __reg_assign_32_into_64().
That's bad and completely unnecessary. Especially __reg_assign_32_into_64()
looks completely out of place here, because we are not performing
zero-extending subregister assignment during conditional jump.
So this patch replaced __reg_combine_* with just a normal
reg_bounds_sync() which will do a proper job of deriving u64/s64 bounds
from u32/s32, and vice versa (among all other combinations).
__reg_combine_64_into_32() is also used in one more place,
coerce_reg_to_size(), while handling 1- and 2-byte register loads.
Looking into this, it seems like besides marking subregister as
unbounded before performing reg_bounds_sync(), we were also performing
deduction of smin32/smax32 and umin32/umax32 bounds from respective
smin/smax and umin/umax bounds. It's now redundant as reg_bounds_sync()
performs all the same logic more generically (e.g., without unnecessary
assumption that upper 32 bits of full register should be zero).
Long story short, we remove __reg_combine_64_into_32() completely, and
coerce_reg_to_size() now only does resetting subreg to unbounded and then
performing reg_bounds_sync() to recover as much information as possible
from 64-bit umin/umax and smin/smax bounds, set explicitly in
coerce_reg_to_size() earlier.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Link: https://lore.kernel.org/r/20231102033759.2541186-10-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko
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d7f0087381 |
bpf: try harder to deduce register bounds from different numeric domains
There are cases (caught by subsequent reg_bounds tests in selftests/bpf) where performing one round of __reg_deduce_bounds() doesn't propagate all the information from, say, s32 to u32 bounds and than from newly learned u32 bounds back to u64 and s64. So perform __reg_deduce_bounds() twice to make sure such derivations are propagated fully after reg_bounds_sync(). One such example is test `(s64)[0xffffffff00000001; 0] (u64)< 0xffffffff00000000` from selftest patch from this patch set. It demonstrates an intricate dance of u64 -> s64 -> u64 -> u32 bounds adjustments, which requires two rounds of __reg_deduce_bounds(). Here are corresponding refinement log from selftest, showing evolution of knowledge. REFINING (FALSE R1) (u64)SRC=[0xffffffff00000000; U64_MAX] (u64)DST_OLD=[0; U64_MAX] (u64)DST_NEW=[0xffffffff00000000; U64_MAX] REFINING (FALSE R1) (u64)SRC=[0xffffffff00000000; U64_MAX] (s64)DST_OLD=[0xffffffff00000001; 0] (s64)DST_NEW=[0xffffffff00000001; -1] REFINING (FALSE R1) (s64)SRC=[0xffffffff00000001; -1] (u64)DST_OLD=[0xffffffff00000000; U64_MAX] (u64)DST_NEW=[0xffffffff00000001; U64_MAX] REFINING (FALSE R1) (u64)SRC=[0xffffffff00000001; U64_MAX] (u32)DST_OLD=[0; U32_MAX] (u32)DST_NEW=[1; U32_MAX] R1 initially has smin/smax set to [0xffffffff00000001; -1], while umin/umax is unknown. After (u64)< comparison, in FALSE branch we gain knowledge that umin/umax is [0xffffffff00000000; U64_MAX]. That causes smin/smax to learn that zero can't happen and upper bound is -1. Then smin/smax is adjusted from umin/umax improving lower bound from 0xffffffff00000000 to 0xffffffff00000001. And then eventually umin32/umax32 bounds are drived from umin/umax and become [1; U32_MAX]. Selftest in the last patch is actually implementing a multi-round fixed-point convergence logic, but so far all the tests are handled by two rounds of reg_bounds_sync() on the verifier state, so we keep it simple for now. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-9-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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c51d5ad654 |
bpf: improve deduction of 64-bit bounds from 32-bit bounds
Add a few interesting cases in which we can tighten 64-bit bounds based on newly learnt information about 32-bit bounds. E.g., when full u64/s64 registers are used in BPF program, and then eventually compared as u32/s32. The latter comparison doesn't change the value of full register, but it does impose new restrictions on possible lower 32 bits of such full registers. And we can use that to derive additional full register bounds information. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Link: https://lore.kernel.org/r/20231102033759.2541186-8-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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6593f2e674 |
bpf: add special smin32/smax32 derivation from 64-bit bounds
Add a special case where we can derive valid s32 bounds from umin/umax or smin/smax by stitching together negative s32 subrange and non-negative s32 subrange. That requires upper 32 bits to form a [N, N+1] range in u32 domain (taking into account wrap around, so 0xffffffff to 0x00000000 is a valid [N, N+1] range in this sense). See code comment for concrete examples. Eduard Zingerman also provided an alternative explanation ([0]) for more mathematically inclined readers: Suppose: . there are numbers a, b, c . 2**31 <= b < 2**32 . 0 <= c < 2**31 . umin = 2**32 * a + b . umax = 2**32 * (a + 1) + c The number of values in the range represented by [umin; umax] is: . N = umax - umin + 1 = 2**32 + c - b + 1 . min(N) = 2**32 + 0 - (2**32-1) + 1 = 2, with b = 2**32-1, c = 0 . max(N) = 2**32 + (2**31 - 1) - 2**31 + 1 = 2**32, with b = 2**31, c = 2**31-1 Hence [(s32)b; (s32)c] forms a valid range. [0] https://lore.kernel.org/bpf/d7af631802f0cfae20df77fe70068702d24bbd31.camel@gmail.com/ Acked-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-7-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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c1efab6468 |
bpf: derive subreg bounds from full bounds when upper 32 bits are constant
Comments in code try to explain the idea behind why this is correct. Please check the code and comments. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-6-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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d540517990 |
bpf: derive smin32/smax32 from umin32/umax32 bounds
All the logic that applies to u64 vs s64, equally applies for u32 vs s32 relationships (just taken in a smaller 32-bit numeric space). So do the same deduction of smin32/smax32 from umin32/umax32, if we can. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-5-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Andrii Nakryiko
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93f7378734 |
bpf: derive smin/smax from umin/max bounds
Add smin/smax derivation from appropriate umin/umax values. Previously the logic was surprisingly asymmetric, trying to derive umin/umax from smin/smax (if possible), but not trying to do the same in the other direction. A simple addition to __reg64_deduce_bounds() fixes this. Added also generic comment about u64/s64 ranges and their relationship. Hopefully that helps readers to understand all the bounds deductions a bit better. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231102033759.2541186-4-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Shung-Hsi Yu
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291d044fd5 |
bpf: Fix precision tracking for BPF_ALU | BPF_TO_BE | BPF_END
BPF_END and BPF_NEG has a different specification for the source bit in
the opcode compared to other ALU/ALU64 instructions, and is either
reserved or use to specify the byte swap endianness. In both cases the
source bit does not encode source operand location, and src_reg is a
reserved field.
backtrack_insn() currently does not differentiate BPF_END and BPF_NEG
from other ALU/ALU64 instructions, which leads to r0 being incorrectly
marked as precise when processing BPF_ALU | BPF_TO_BE | BPF_END
instructions. This commit teaches backtrack_insn() to correctly mark
precision for such case.
While precise tracking of BPF_NEG and other BPF_END instructions are
correct and does not need fixing, this commit opt to process all BPF_NEG
and BPF_END instructions within the same if-clause to better align with
current convention used in the verifier (e.g. check_alu_op).
Fixes:
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Chuyi Zhou
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3091b66749 |
bpf: Relax allowlist for css_task iter
The newly added open-coded css_task iter would try to hold the global
css_set_lock in bpf_iter_css_task_new, so the bpf side has to be careful in
where it allows to use this iter. The mainly concern is dead locking on
css_set_lock. check_css_task_iter_allowlist() in verifier enforced css_task
can only be used in bpf_lsm hooks and sleepable bpf_iter.
This patch relax the allowlist for css_task iter. Any lsm and any iter
(even non-sleepable) and any sleepable are safe since they would not hold
the css_set_lock before entering BPF progs context.
This patch also fixes the misused BPF_TRACE_ITER in
check_css_task_iter_allowlist which compared bpf_prog_type with
bpf_attach_type.
Fixes:
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Hao Sun
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811c363645 |
bpf: Fix check_stack_write_fixed_off() to correctly spill imm
In check_stack_write_fixed_off(), imm value is cast to u32 before being
spilled to the stack. Therefore, the sign information is lost, and the
range information is incorrect when load from the stack again.
For the following prog:
0: r2 = r10
1: *(u64*)(r2 -40) = -44
2: r0 = *(u64*)(r2 - 40)
3: if r0 s<= 0xa goto +2
4: r0 = 1
5: exit
6: r0 = 0
7: exit
The verifier gives:
func#0 @0
0: R1=ctx(off=0,imm=0) R10=fp0
0: (bf) r2 = r10 ; R2_w=fp0 R10=fp0
1: (7a) *(u64 *)(r2 -40) = -44 ; R2_w=fp0 fp-40_w=4294967252
2: (79) r0 = *(u64 *)(r2 -40) ; R0_w=4294967252 R2_w=fp0
fp-40_w=4294967252
3: (c5) if r0 s< 0xa goto pc+2
mark_precise: frame0: last_idx 3 first_idx 0 subseq_idx -1
mark_precise: frame0: regs=r0 stack= before 2: (79) r0 = *(u64 *)(r2 -40)
3: R0_w=4294967252
4: (b7) r0 = 1 ; R0_w=1
5: (95) exit
verification time 7971 usec
stack depth 40
processed 6 insns (limit 1000000) max_states_per_insn 0 total_states 0
peak_states 0 mark_read 0
So remove the incorrect cast, since imm field is declared as s32, and
__mark_reg_known() takes u64, so imm would be correctly sign extended
by compiler.
Fixes:
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Matthieu Baerts
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05670f81d1 |
bpf: fix compilation error without CGROUPS
Our MPTCP CI complained [1] -- and KBuild too -- that it was no longer
possible to build the kernel without CONFIG_CGROUPS:
kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_new':
kernel/bpf/task_iter.c:919:14: error: 'CSS_TASK_ITER_PROCS' undeclared (first use in this function)
919 | case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED:
| ^~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c:919:14: note: each undeclared identifier is reported only once for each function it appears in
kernel/bpf/task_iter.c:919:36: error: 'CSS_TASK_ITER_THREADED' undeclared (first use in this function)
919 | case CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED:
| ^~~~~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c:927:60: error: invalid application of 'sizeof' to incomplete type 'struct css_task_iter'
927 | kit->css_it = bpf_mem_alloc(&bpf_global_ma, sizeof(struct css_task_iter));
| ^~~~~~
kernel/bpf/task_iter.c:930:9: error: implicit declaration of function 'css_task_iter_start'; did you mean 'task_seq_start'? [-Werror=implicit-function-declaration]
930 | css_task_iter_start(css, flags, kit->css_it);
| ^~~~~~~~~~~~~~~~~~~
| task_seq_start
kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_next':
kernel/bpf/task_iter.c:940:16: error: implicit declaration of function 'css_task_iter_next'; did you mean 'class_dev_iter_next'? [-Werror=implicit-function-declaration]
940 | return css_task_iter_next(kit->css_it);
| ^~~~~~~~~~~~~~~~~~
| class_dev_iter_next
kernel/bpf/task_iter.c:940:16: error: returning 'int' from a function with return type 'struct task_struct *' makes pointer from integer without a cast [-Werror=int-conversion]
940 | return css_task_iter_next(kit->css_it);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/bpf/task_iter.c: In function 'bpf_iter_css_task_destroy':
kernel/bpf/task_iter.c:949:9: error: implicit declaration of function 'css_task_iter_end' [-Werror=implicit-function-declaration]
949 | css_task_iter_end(kit->css_it);
| ^~~~~~~~~~~~~~~~~
This patch simply surrounds with a #ifdef the new code requiring CGroups
support. It seems enough for the compiler and this is similar to
bpf_iter_css_{new,next,destroy}() functions where no other #ifdef have
been added in kernel/bpf/helpers.c and in the selftests.
Fixes:
|
||
|
Andrii Nakryiko
|
42d31dd601 |
bpf: Improve JEQ/JNE branch taken logic
When determining if an if/else branch will always or never be taken, use signed range knowledge in addition to currently used unsigned range knowledge. If either signed or unsigned range suggests that condition is always/never taken, return corresponding branch_taken verdict. Current use of unsigned range for this seems arbitrary and unnecessarily incomplete. It is possible for *signed* operations to be performed on register, which could "invalidate" unsigned range for that register. In such case branch_taken will be artificially useless, even if we can still tell that some constant is outside of register value range based on its signed bounds. veristat-based validation shows zero differences across selftests, Cilium, and Meta-internal BPF object files. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com> Link: https://lore.kernel.org/bpf/20231022205743.72352-2-andrii@kernel.org |
||
Eduard Zingerman
|
b4d8239534 |
bpf: print full verifier states on infinite loop detection
Additional logging in is_state_visited(): if infinite loop is detected print full verifier state for both current and equivalent states. Acked-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20231024000917.12153-8-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Eduard Zingerman
|
2a0992829e |
bpf: correct loop detection for iterators convergence
It turns out that .branches > 0 in is_state_visited() is not a
sufficient condition to identify if two verifier states form a loop
when iterators convergence is computed. This commit adds logic to
distinguish situations like below:
(I) initial (II) initial
| |
V V
.---------> hdr ..
| | |
| V V
| .------... .------..
| | | | |
| V V V V
| ... ... .-> hdr ..
| | | | | |
| V V | V V
| succ <- cur | succ <- cur
| | | |
| V | V
| ... | ...
| | | |
'----' '----'
For both (I) and (II) successor 'succ' of the current state 'cur' was
previously explored and has branches count at 0. However, loop entry
'hdr' corresponding to 'succ' might be a part of current DFS path.
If that is the case 'succ' and 'cur' are members of the same loop
and have to be compared exactly.
Co-developed-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Co-developed-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Reviewed-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20231024000917.12153-6-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Eduard Zingerman
|
2793a8b015 |
bpf: exact states comparison for iterator convergence checks
Convergence for open coded iterators is computed in is_state_visited()
by examining states with branches count > 1 and using states_equal().
states_equal() computes sub-state relation using read and precision marks.
Read and precision marks are propagated from children states,
thus are not guaranteed to be complete inside a loop when branches
count > 1. This could be demonstrated using the following unsafe program:
1. r7 = -16
2. r6 = bpf_get_prandom_u32()
3. while (bpf_iter_num_next(&fp[-8])) {
4. if (r6 != 42) {
5. r7 = -32
6. r6 = bpf_get_prandom_u32()
7. continue
8. }
9. r0 = r10
10. r0 += r7
11. r8 = *(u64 *)(r0 + 0)
12. r6 = bpf_get_prandom_u32()
13. }
Here verifier would first visit path 1-3, create a checkpoint at 3
with r7=-16, continue to 4-7,3 with r7=-32.
Because instructions at 9-12 had not been visitied yet existing
checkpoint at 3 does not have read or precision mark for r7.
Thus states_equal() would return true and verifier would discard
current state, thus unsafe memory access at 11 would not be caught.
This commit fixes this loophole by introducing exact state comparisons
for iterator convergence logic:
- registers are compared using regs_exact() regardless of read or
precision marks;
- stack slots have to have identical type.
Unfortunately, this is too strict even for simple programs like below:
i = 0;
while(iter_next(&it))
i++;
At each iteration step i++ would produce a new distinct state and
eventually instruction processing limit would be reached.
To avoid such behavior speculatively forget (widen) range for
imprecise scalar registers, if those registers were not precise at the
end of the previous iteration and do not match exactly.
This a conservative heuristic that allows to verify wide range of
programs, however it precludes verification of programs that conjure
an imprecise value on the first loop iteration and use it as precise
on the second.
Test case iter_task_vma_for_each() presents one of such cases:
unsigned int seen = 0;
...
bpf_for_each(task_vma, vma, task, 0) {
if (seen >= 1000)
break;
...
seen++;
}
Here clang generates the following code:
<LBB0_4>:
24: r8 = r6 ; stash current value of
... body ... 'seen'
29: r1 = r10
30: r1 += -0x8
31: call bpf_iter_task_vma_next
32: r6 += 0x1 ; seen++;
33: if r0 == 0x0 goto +0x2 <LBB0_6> ; exit on next() == NULL
34: r7 += 0x10
35: if r8 < 0x3e7 goto -0xc <LBB0_4> ; loop on seen < 1000
<LBB0_6>:
... exit ...
Note that counter in r6 is copied to r8 and then incremented,
conditional jump is done using r8. Because of this precision mark for
r6 lags one state behind of precision mark on r8 and widening logic
kicks in.
Adding barrier_var(seen) after conditional is sufficient to force
clang use the same register for both counting and conditional jump.
This issue was discussed in the thread [1] which was started by
Andrew Werner <awerner32@gmail.com> demonstrating a similar bug
in callback functions handling. The callbacks would be addressed
in a followup patch.
[1] https://lore.kernel.org/bpf/97a90da09404c65c8e810cf83c94ac703705dc0e.camel@gmail.com/
Co-developed-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Co-developed-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20231024000917.12153-4-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Eduard Zingerman
|
4c97259abc |
bpf: extract same_callsites() as utility function
Extract same_callsites() from clean_live_states() as a utility function. This function would be used by the next patch in the set. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20231024000917.12153-3-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Eduard Zingerman
|
3c4e420cb6 |
bpf: move explored_state() closer to the beginning of verifier.c
Subsequent patches would make use of explored_state() function. Move it up to avoid adding unnecessary prototype. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20231024000917.12153-2-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Chuyi Zhou
|
cb3ecf7915 |
bpf: Let bpf_iter_task_new accept null task ptr
When using task_iter to iterate all threads of a specific task, we enforce
that the user must pass a valid task pointer to ensure safety. However,
when iterating all threads/process in the system, BPF verifier still
require a valid ptr instead of "nullable" pointer, even though it's
pointless, which is a kind of surprising from usability standpoint. It
would be nice if we could let that kfunc accept a explicit null pointer
when we are using BPF_TASK_ITER_ALL_{PROCS, THREADS} and a valid pointer
when using BPF_TASK_ITER_THREAD.
Given a trival kfunc:
__bpf_kfunc void FN(struct TYPE_A *obj);
BPF Prog would reject a nullptr for obj. The error info is:
"arg#x pointer type xx xx must point to scalar, or struct with scalar"
reported by get_kfunc_ptr_arg_type(). The reg->type is SCALAR_VALUE and
the btf type of ref_t is not scalar or scalar_struct which leads to the
rejection of get_kfunc_ptr_arg_type.
This patch add "__nullable" annotation:
__bpf_kfunc void FN(struct TYPE_A *obj__nullable);
Here __nullable indicates obj can be optional, user can pass a explicit
nullptr or a normal TYPE_A pointer. In get_kfunc_ptr_arg_type(), we will
detect whether the current arg is optional and register is null, If so,
return a new kfunc_ptr_arg_type KF_ARG_PTR_TO_NULL and skip to the next
arg in check_kfunc_args().
Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231018061746.111364-7-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Chuyi Zhou
|
dfab99df14 |
bpf: teach the verifier to enforce css_iter and task_iter in RCU CS
css_iter and task_iter should be used in rcu section. Specifically, in sleepable progs explicit bpf_rcu_read_lock() is needed before use these iters. In normal bpf progs that have implicit rcu_read_lock(), it's OK to use them directly. This patch adds a new a KF flag KF_RCU_PROTECTED for bpf_iter_task_new and bpf_iter_css_new. It means the kfunc should be used in RCU CS. We check whether we are in rcu cs before we want to invoke this kfunc. If the rcu protection is guaranteed, we would let st->type = PTR_TO_STACK | MEM_RCU. Once user do rcu_unlock during the iteration, state MEM_RCU of regs would be cleared. is_iter_reg_valid_init() will reject if reg->type is UNTRUSTED. It is worth noting that currently, bpf_rcu_read_unlock does not clear the state of the STACK_ITER reg, since bpf_for_each_spilled_reg only considers STACK_SPILL. This patch also let bpf_for_each_spilled_reg search STACK_ITER. Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231018061746.111364-6-zhouchuyi@bytedance.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Chuyi Zhou
|
9c66dc94b6 |
bpf: Introduce css_task open-coded iterator kfuncs
This patch adds kfuncs bpf_iter_css_task_{new,next,destroy} which allow
creation and manipulation of struct bpf_iter_css_task in open-coded
iterator style. These kfuncs actually wrapps css_task_iter_{start,next,
end}. BPF programs can use these kfuncs through bpf_for_each macro for
iteration of all tasks under a css.
css_task_iter_*() would try to get the global spin-lock *css_set_lock*, so
the bpf side has to be careful in where it allows to use this iter.
Currently we only allow it in bpf_lsm and bpf iter-s.
Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20231018061746.111364-3-zhouchuyi@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
Jakub Kicinski
|
a3c2dd9648 |
bpf-next-for-netdev
-----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQTFp0I1jqZrAX+hPRXbK58LschIgwUCZS1d4wAKCRDbK58LschI g4DSAP441CdKh8fd+wNKUSKHFbpCQ6EvocR6Nf+Sj2DFUx/w/QEA7mfju7Abqjc3 xwDEx0BuhrjMrjV5MmEpxc7lYl9XcQU= =vuWk -----END PGP SIGNATURE----- Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next Daniel Borkmann says: ==================== pull-request: bpf-next 2023-10-16 We've added 90 non-merge commits during the last 25 day(s) which contain a total of 120 files changed, 3519 insertions(+), 895 deletions(-). The main changes are: 1) Add missed stats for kprobes to retrieve the number of missed kprobe executions and subsequent executions of BPF programs, from Jiri Olsa. 2) Add cgroup BPF sockaddr hooks for unix sockets. The use case is for systemd to reimplement the LogNamespace feature which allows running multiple instances of systemd-journald to process the logs of different services, from Daan De Meyer. 3) Implement BPF CPUv4 support for s390x BPF JIT, from Ilya Leoshkevich. 4) Improve BPF verifier log output for scalar registers to better disambiguate their internal state wrt defaults vs min/max values matching, from Andrii Nakryiko. 5) Extend the BPF fib lookup helpers for IPv4/IPv6 to support retrieving the source IP address with a new BPF_FIB_LOOKUP_SRC flag, from Martynas Pumputis. 6) Add support for open-coded task_vma iterator to help with symbolization for BPF-collected user stacks, from Dave Marchevsky. 7) Add libbpf getters for accessing individual BPF ring buffers which is useful for polling them individually, for example, from Martin Kelly. 8) Extend AF_XDP selftests to validate the SHARED_UMEM feature, from Tushar Vyavahare. 9) Improve BPF selftests cross-building support for riscv arch, from Björn Töpel. 10) Add the ability to pin a BPF timer to the same calling CPU, from David Vernet. 11) Fix libbpf's bpf_tracing.h macros for riscv to use the generic implementation of PT_REGS_SYSCALL_REGS() to access syscall arguments, from Alexandre Ghiti. 12) Extend libbpf to support symbol versioning for uprobes, from Hengqi Chen. 13) Fix bpftool's skeleton code generation to guarantee that ELF data is 8 byte aligned, from Ian Rogers. 14) Inherit system-wide cpu_mitigations_off() setting for Spectre v1/v4 security mitigations in BPF verifier, from Yafang Shao. 15) Annotate struct bpf_stack_map with __counted_by attribute to prepare BPF side for upcoming __counted_by compiler support, from Kees Cook. * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (90 commits) bpf: Ensure proper register state printing for cond jumps bpf: Disambiguate SCALAR register state output in verifier logs selftests/bpf: Make align selftests more robust selftests/bpf: Improve missed_kprobe_recursion test robustness selftests/bpf: Improve percpu_alloc test robustness selftests/bpf: Add tests for open-coded task_vma iter bpf: Introduce task_vma open-coded iterator kfuncs selftests/bpf: Rename bpf_iter_task_vma.c to bpf_iter_task_vmas.c bpf: Don't explicitly emit BTF for struct btf_iter_num bpf: Change syscall_nr type to int in struct syscall_tp_t net/bpf: Avoid unused "sin_addr_len" warning when CONFIG_CGROUP_BPF is not set bpf: Avoid unnecessary audit log for CPU security mitigations selftests/bpf: Add tests for cgroup unix socket address hooks selftests/bpf: Make sure mount directory exists documentation/bpf: Document cgroup unix socket address hooks bpftool: Add support for cgroup unix socket address hooks libbpf: Add support for cgroup unix socket address hooks bpf: Implement cgroup sockaddr hooks for unix sockets bpf: Add bpf_sock_addr_set_sun_path() to allow writing unix sockaddr from bpf bpf: Propagate modified uaddrlen from cgroup sockaddr programs ... ==================== Link: https://lore.kernel.org/r/20231016204803.30153-1-daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
||
|
Andrii Nakryiko
|
1a8a315f00 |
bpf: Ensure proper register state printing for cond jumps
Verifier emits relevant register state involved in any given instruction next to it after `;` to the right, if possible. Or, worst case, on the separate line repeating instruction index. E.g., a nice and simple case would be: 2: (d5) if r0 s<= 0x0 goto pc+1 ; R0_w=0 But if there is some intervening extra output (e.g., precision backtracking log) involved, we are supposed to see the state after the precision backtrack log: 4: (75) if r0 s>= 0x0 goto pc+1 mark_precise: frame0: last_idx 4 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r0 stack= before 2: (d5) if r0 s<= 0x0 goto pc+1 mark_precise: frame0: regs=r0 stack= before 1: (b7) r0 = 0 6: R0_w=0 First off, note that in `6: R0_w=0` instruction index corresponds to the next instruction, not to the conditional jump instruction itself, which is wrong and we'll get to that. But besides that, the above is a happy case that does work today. Yet, if it so happens that precision backtracking had to traverse some of the parent states, this `6: R0_w=0` state output would be missing. This is due to a quirk of print_verifier_state() routine, which performs mark_verifier_state_clean(env) at the end. This marks all registers as "non-scratched", which means that subsequent logic to print *relevant* registers (that is, "scratched ones") fails and doesn't see anything relevant to print and skips the output altogether. print_verifier_state() is used both to print instruction context, but also to print an **entire** verifier state indiscriminately, e.g., during precision backtracking (and in a few other situations, like during entering or exiting subprogram). Which means if we have to print entire parent state before getting to printing instruction context state, instruction context is marked as clean and is omitted. Long story short, this is definitely not intentional. So we fix this behavior in this patch by teaching print_verifier_state() to clear scratch state only if it was used to print instruction state, not the parent/callback state. This is determined by print_all option, so if it's not set, we don't clear scratch state. This fixes missing instruction state for these cases. As for the mismatched instruction index, we fix that by making sure we call print_insn_state() early inside check_cond_jmp_op() before we adjusted insn_idx based on jump branch taken logic. And with that we get desired correct information: 9: (16) if w4 == 0x1 goto pc+9 mark_precise: frame0: last_idx 9 first_idx 9 subseq_idx -1 mark_precise: frame0: parent state regs=r4 stack=: R2_w=1944 R4_rw=P1 R10=fp0 mark_precise: frame0: last_idx 8 first_idx 0 subseq_idx 9 mark_precise: frame0: regs=r4 stack= before 8: (66) if w4 s> 0x3 goto pc+5 mark_precise: frame0: regs=r4 stack= before 7: (b7) r4 = 1 9: R4=1 Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20231011223728.3188086-6-andrii@kernel.org |
||
|
Andrii Nakryiko
|
72f8a1de4a |
bpf: Disambiguate SCALAR register state output in verifier logs
Currently the way that verifier prints SCALAR_VALUE register state (and
PTR_TO_PACKET, which can have var_off and ranges info as well) is very
ambiguous.
In the name of brevity we are trying to eliminate "unnecessary" output
of umin/umax, smin/smax, u32_min/u32_max, and s32_min/s32_max values, if
possible. Current rules are that if any of those have their default
value (which for mins is the minimal value of its respective types: 0,
S32_MIN, or S64_MIN, while for maxs it's U32_MAX, S32_MAX, S64_MAX, or
U64_MAX) *OR* if there is another min/max value that as matching value.
E.g., if smin=100 and umin=100, we'll emit only umin=10, omitting smin
altogether. This approach has a few problems, being both ambiguous and
sort-of incorrect in some cases.
Ambiguity is due to missing value could be either default value or value
of umin/umax or smin/smax. This is especially confusing when we mix
signed and unsigned ranges. Quite often, umin=0 and smin=0, and so we'll
have only `umin=0` leaving anyone reading verifier log to guess whether
smin is actually 0 or it's actually -9223372036854775808 (S64_MIN). And
often times it's important to know, especially when debugging tricky
issues.
"Sort-of incorrectness" comes from mixing negative and positive values.
E.g., if umin is some large positive number, it can be equal to smin
which is, interpreted as signed value, is actually some negative value.
Currently, that smin will be omitted and only umin will be emitted with
a large positive value, giving an impression that smin is also positive.
Anyway, ambiguity is the biggest issue making it impossible to have an
exact understanding of register state, preventing any sort of automated
testing of verifier state based on verifier log. This patch is
attempting to rectify the situation by removing ambiguity, while
minimizing the verboseness of register state output.
The rules are straightforward:
- if some of the values are missing, then it definitely has a default
value. I.e., `umin=0` means that umin is zero, but smin is actually
S64_MIN;
- all the various boundaries that happen to have the same value are
emitted in one equality separated sequence. E.g., if umin and smin are
both 100, we'll emit `smin=umin=100`, making this explicit;
- we do not mix negative and positive values together, and even if
they happen to have the same bit-level value, they will be emitted
separately with proper sign. I.e., if both umax and smax happen to be
0xffffffffffffffff, we'll emit them both separately as
`smax=-1,umax=18446744073709551615`;
- in the name of a bit more uniformity and consistency,
{u32,s32}_{min,max} are renamed to {s,u}{min,max}32, which seems to
improve readability.
The above means that in case of all 4 ranges being, say, [50, 100] range,
we'd previously see hugely ambiguous:
R1=scalar(umin=50,umax=100)
Now, we'll be more explicit:
R1=scalar(smin=umin=smin32=umin32=50,smax=umax=smax32=umax32=100)
This is slightly more verbose, but distinct from the case when we don't
know anything about signed boundaries and 32-bit boundaries, which under
new rules will match the old case:
R1=scalar(umin=50,umax=100)
Also, in the name of simplicity of implementation and consistency, order
for {s,u}32_{min,max} are emitted *before* var_off. Previously they were
emitted afterwards, for unclear reasons.
This patch also includes a few fixes to selftests that expect exact
register state to accommodate slight changes to verifier format. You can
see that the changes are pretty minimal in common cases.
Note, the special case when SCALAR_VALUE register is a known constant
isn't changed, we'll emit constant value once, interpreted as signed
value.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20231011223728.3188086-5-andrii@kernel.org
|
||
|
Jakub Kicinski
|
0e6bb5b7f4 |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Cross-merge networking fixes after downstream PR. No conflicts. Adjacent changes: kernel/bpf/verifier.c |
||
Daan De Meyer
|
859051dd16 |
bpf: Implement cgroup sockaddr hooks for unix sockets
These hooks allows intercepting connect(), getsockname(), getpeername(), sendmsg() and recvmsg() for unix sockets. The unix socket hooks get write access to the address length because the address length is not fixed when dealing with unix sockets and needs to be modified when a unix socket address is modified by the hook. Because abstract socket unix addresses start with a NUL byte, we cannot recalculate the socket address in kernelspace after running the hook by calculating the length of the unix socket path using strlen(). These hooks can be used when users want to multiplex syscall to a single unix socket to multiple different processes behind the scenes by redirecting the connect() and other syscalls to process specific sockets. We do not implement support for intercepting bind() because when using bind() with unix sockets with a pathname address, this creates an inode in the filesystem which must be cleaned up. If we rewrite the address, the user might try to clean up the wrong file, leaking the socket in the filesystem where it is never cleaned up. Until we figure out a solution for this (and a use case for intercepting bind()), we opt to not allow rewriting the sockaddr in bind() calls. We also implement recvmsg() support for connected streams so that after a connect() that is modified by a sockaddr hook, any corresponding recmvsg() on the connected socket can also be modified to make the connected program think it is connected to the "intended" remote. Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com> Link: https://lore.kernel.org/r/20231011185113.140426-5-daan.j.demeyer@gmail.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> |
||
David Vernet
|
829955981c |
bpf: Fix verifier log for async callback return values
The verifier, as part of check_return_code(), verifies that async
callbacks such as from e.g. timers, will return 0. It does this by
correctly checking that R0->var_off is in tnum_const(0), which
effectively checks that it's in a range of 0. If this condition fails,
however, it prints an error message which says that the value should
have been in (0x0; 0x1). This results in possibly confusing output such
as the following in which an async callback returns 1:
At async callback the register R0 has value (0x1; 0x0) should have been in (0x0; 0x1)
The fix is easy -- we should just pass the tnum_const(0) as the correct
range to verbose_invalid_scalar(), which will then print the following:
At async callback the register R0 has value (0x1; 0x0) should have been in (0x0; 0x0)
Fixes:
|
||
|
Jakub Kicinski
|
2606cf059c |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Cross-merge networking fixes after downstream PR. No conflicts (or adjacent changes of note). Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
||
Ilya Leoshkevich
|
577c06af81 |
bpf: Disable zero-extension for BPF_MEMSX
On the architectures that use bpf_jit_needs_zext(), e.g., s390x, the
verifier incorrectly inserts a zero-extension after BPF_MEMSX, leading
to miscompilations like the one below:
24: 89 1a ff fe 00 00 00 00 "r1 = *(s16 *)(r10 - 2);" # zext_dst set
0x3ff7fdb910e: lgh %r2,-2(%r13,%r0) # load halfword
0x3ff7fdb9114: llgfr %r2,%r2 # wrong!
25: 65 10 00 03 00 00 7f ff if r1 s> 32767 goto +3 <l0_1> # check_cond_jmp_op()
Disable such zero-extensions. The JITs need to insert sign-extension
themselves, if necessary.
Suggested-by: Puranjay Mohan <puranjay12@gmail.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Puranjay Mohan <puranjay12@gmail.com>
Link: https://lore.kernel.org/r/20230919101336.2223655-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Andrii Nakryiko
|
81335f90e8 |
bpf: unconditionally reset backtrack_state masks on global func exit
In mark_chain_precision() logic, when we reach the entry to a global
func, it is expected that R1-R5 might be still requested to be marked
precise. This would correspond to some integer input arguments being
tracked as precise. This is all expected and handled as a special case.
What's not expected is that we'll leave backtrack_state structure with
some register bits set. This is because for subsequent precision
propagations backtrack_state is reused without clearing masks, as all
code paths are carefully written in a way to leave empty backtrack_state
with zeroed out masks, for speed.
The fix is trivial, we always clear register bit in the register mask, and
then, optionally, set reg->precise if register is SCALAR_VALUE type.
Reported-by: Chris Mason <clm@meta.com>
Fixes:
|
||
Alexei Starovoitov
|
aec42f3623 |
bpf: Remove unused variables.
Remove unused prev_offset, min_size, krec_size variables.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202309190634.fL17FWoT-lkp@intel.com/
Fixes:
|
||
Kumar Kartikeya Dwivedi
|
06d686f771 |
bpf: Fix kfunc callback register type handling
The kfunc code to handle KF_ARG_PTR_TO_CALLBACK does not check the reg
type before using reg->subprogno. This can accidently permit invalid
pointers from being passed into callback helpers (e.g. silently from
different paths). Likewise, reg->subprogno from the per-register type
union may not be meaningful either. We need to reject any other type
except PTR_TO_FUNC.
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Fixes:
|
||
|
Kumar Kartikeya Dwivedi
|
fd548e1a46 |
bpf: Disallow fentry/fexit/freplace for exception callbacks
During testing, it was discovered that extensions to exception callbacks had no checks, upon running a testcase, the kernel ended up running off the end of a program having final call as bpf_throw, and hitting int3 instructions. The reason is that while the default exception callback would have reset the stack frame to return back to the main program's caller, the replacing extension program will simply return back to bpf_throw, which will instead return back to the program and the program will continue execution, now in an undefined state where anything could happen. The way to support extensions to an exception callback would be to mark the BPF_PROG_TYPE_EXT main subprog as an exception_cb, and prevent it from calling bpf_throw. This would make the JIT produce a prologue that restores saved registers and reset the stack frame. But let's not do that until there is a concrete use case for this, and simply disallow this for now. Similar issues will exist for fentry and fexit cases, where trampoline saves data on the stack when invoking exception callback, which however will then end up resetting the stack frame, and on return, the fexit program will never will invoked as the return address points to the main program's caller in the kernel. Instead of additional complexity and back and forth between the two stacks to enable such a use case, simply forbid it. One key point here to note is that currently X86_TAIL_CALL_OFFSET didn't require any modifications, even though we emit instructions before the corresponding endbr64 instruction. This is because we ensure that a main subprog never serves as an exception callback, and therefore the exception callback (which will be a global subprog) can never serve as the tail call target, eliminating any discrepancies. However, once we support a BPF_PROG_TYPE_EXT to also act as an exception callback, it will end up requiring change to the tail call offset to account for the extra instructions. For simplicitly, tail calls could be disabled for such targets. Noting the above, it appears better to wait for a concrete use case before choosing to permit extension programs to replace exception callbacks. As a precaution, we disable fentry and fexit for exception callbacks as well. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-13-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
a923819fb2 |
bpf: Treat first argument as return value for bpf_throw
In case of the default exception callback, change the behavior of bpf_throw, where the passed cookie value is no longer ignored, but is instead the return value of the default exception callback. As such, we need to place restrictions on the value being passed into bpf_throw in such a case, only allowing those permitted by the check_return_code function. Thus, bpf_throw can now control the return value of the program from each call site without having the user install a custom exception callback just to override the return value when an exception is thrown. We also modify the hidden subprog instructions to now move BPF_REG_1 to BPF_REG_0, so as to set the return value before exit in the default callback. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-9-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
b62bf8a5e9 |
bpf: Perform CFG walk for exception callback
Since exception callbacks are not referenced using bpf_pseudo_func and bpf_pseudo_call instructions, check_cfg traversal will never explore instructions of the exception callback. Even after adding the subprog, the program will then fail with a 'unreachable insn' error. We thus need to begin walking from the start of the exception callback again in check_cfg after a complete CFG traversal finishes, so as to explore the CFG rooted at the exception callback. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-8-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
b9ae0c9dd0 |
bpf: Add support for custom exception callbacks
By default, the subprog generated by the verifier to handle a thrown exception hardcodes a return value of 0. To allow user-defined logic and modification of the return value when an exception is thrown, introduce the 'exception_callback:' declaration tag, which marks a callback as the default exception handler for the program. The format of the declaration tag is 'exception_callback:<value>', where <value> is the name of the exception callback. Each main program can be tagged using this BTF declaratiion tag to associate it with an exception callback. In case the tag is absent, the default callback is used. As such, the exception callback cannot be modified at runtime, only set during verification. Allowing modification of the callback for the current program execution at runtime leads to issues when the programs begin to nest, as any per-CPU state maintaing this information will have to be saved and restored. We don't want it to stay in bpf_prog_aux as this takes a global effect for all programs. An alternative solution is spilling the callback pointer at a known location on the program stack on entry, and then passing this location to bpf_throw as a parameter. However, since exceptions are geared more towards a use case where they are ideally never invoked, optimizing for this use case and adding to the complexity has diminishing returns. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
aaa619ebcc |
bpf: Refactor check_btf_func and split into two phases
This patch splits the check_btf_info's check_btf_func check into two separate phases. The first phase sets up the BTF and prepares func_info, but does not perform any validation of required invariants for subprogs just yet. This is left to the second phase, which happens where check_btf_info executes currently, and performs the line_info and CO-RE relocation. The reason to perform this split is to obtain the userspace supplied func_info information before we perform the add_subprog call, where we would now require finding and adding subprogs that may not have a bpf_pseudo_call or bpf_pseudo_func instruction in the program. We require this as we want to enable userspace to supply exception callbacks that can override the default hidden subprogram generated by the verifier (which performs a hardcoded action). In such a case, the exception callback may never be referenced in an instruction, but will still be suitably annotated (by way of BTF declaration tags). For finding this exception callback, we would require the program's BTF information, and the supplied func_info information which maps BTF type IDs to subprograms. Since the exception callback won't actually be referenced through instructions, later checks in check_cfg and do_check_subprogs will not verify the subprog. This means that add_subprog needs to add them in the add_subprog_and_kfunc phase before we move forward, which is why the BTF and func_info are required at that point. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-6-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
f18b03faba |
bpf: Implement BPF exceptions
This patch implements BPF exceptions, and introduces a bpf_throw kfunc to allow programs to throw exceptions during their execution at runtime. A bpf_throw invocation is treated as an immediate termination of the program, returning back to its caller within the kernel, unwinding all stack frames. This allows the program to simplify its implementation, by testing for runtime conditions which the verifier has no visibility into, and assert that they are true. In case they are not, the program can simply throw an exception from the other branch. BPF exceptions are explicitly *NOT* an unlikely slowpath error handling primitive, and this objective has guided design choices of the implementation of the them within the kernel (with the bulk of the cost for unwinding the stack offloaded to the bpf_throw kfunc). The implementation of this mechanism requires use of add_hidden_subprog mechanism introduced in the previous patch, which generates a couple of instructions to move R1 to R0 and exit. The JIT then rewrites the prologue of this subprog to take the stack pointer and frame pointer as inputs and reset the stack frame, popping all callee-saved registers saved by the main subprog. The bpf_throw function then walks the stack at runtime, and invokes this exception subprog with the stack and frame pointers as parameters. Reviewers must take note that currently the main program is made to save all callee-saved registers on x86_64 during entry into the program. This is because we must do an equivalent of a lightweight context switch when unwinding the stack, therefore we need the callee-saved registers of the caller of the BPF program to be able to return with a sane state. Note that we have to additionally handle r12, even though it is not used by the program, because when throwing the exception the program makes an entry into the kernel which could clobber r12 after saving it on the stack. To be able to preserve the value we received on program entry, we push r12 and restore it from the generated subprogram when unwinding the stack. For now, bpf_throw invocation fails when lingering resources or locks exist in that path of the program. In a future followup, bpf_throw will be extended to perform frame-by-frame unwinding to release lingering resources for each stack frame, removing this limitation. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-5-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
335d1c5b54 |
bpf: Implement support for adding hidden subprogs
Introduce support in the verifier for generating a subprogram and include it as part of a BPF program dynamically after the do_check phase is complete. The first user will be the next patch which generates default exception callbacks if none are set for the program. The phase of invocation will be do_misc_fixups. Note that this is an internal verifier function, and should be used with instruction blocks which uphold the invariants stated in check_subprogs. Since these subprogs are always appended to the end of the instruction sequence of the program, it becomes relatively inexpensive to do the related adjustments to the subprog_info of the program. Only the fake exit subprogram is shifted forward, making room for our new subprog. This is useful to insert a new subprogram, get it JITed, and obtain its function pointer. The next patch will use this functionality to insert a default exception callback which will be invoked after unwinding the stack. Note that these added subprograms are invisible to userspace, and never reported in BPF_OBJ_GET_INFO_BY_ID etc. For now, only a single subprogram is supported, but more can be easily supported in the future. To this end, two function counts are introduced now, the existing func_cnt, and real_func_cnt, the latter including hidden programs. This allows us to conver the JIT code to use the real_func_cnt for management of resources while syscall path continues working with existing func_cnt. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230912233214.1518551-4-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
Leon Hwang
|
2b5dcb31a1 |
bpf, x64: Fix tailcall infinite loop
From commit |
||
Yonghong Song
|
5b221ecb3a |
bpf: Mark OBJ_RELEASE argument as MEM_RCU when possible
In previous selftests/bpf patch, we have
p = bpf_percpu_obj_new(struct val_t);
if (!p)
goto out;
p1 = bpf_kptr_xchg(&e->pc, p);
if (p1) {
/* race condition */
bpf_percpu_obj_drop(p1);
}
p = e->pc;
if (!p)
goto out;
After bpf_kptr_xchg(), we need to re-read e->pc into 'p'.
This is due to that the second argument of bpf_kptr_xchg() is marked
OBJ_RELEASE and it will be marked as invalid after the call.
So after bpf_kptr_xchg(), 'p' is an unknown scalar,
and the bpf program needs to reread from the map value.
This patch checks if the 'p' has type MEM_ALLOC and MEM_PERCPU,
and if 'p' is RCU protected. If this is the case, 'p' can be marked
as MEM_RCU. MEM_ALLOC needs to be removed since 'p' is not
an owning reference any more. Such a change makes re-read
from the map value unnecessary.
Note that re-reading 'e->pc' after bpf_kptr_xchg() might get
a different value from 'p' if immediately before 'p = e->pc',
another cpu may do another bpf_kptr_xchg() and swap in another value
into 'e->pc'. If this is the case, then 'p = e->pc' may
get either 'p' or another value, and race condition already exists.
So removing direct re-reading seems fine too.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230827152816.2000760-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Yonghong Song
|
01cc55af93 |
bpf: Add bpf_this_cpu_ptr/bpf_per_cpu_ptr support for allocated percpu obj
The bpf helpers bpf_this_cpu_ptr() and bpf_per_cpu_ptr() are re-purposed for allocated percpu objects. For an allocated percpu obj, the reg type is 'PTR_TO_BTF_ID | MEM_PERCPU | MEM_RCU'. The return type for these two re-purposed helpera is 'PTR_TO_MEM | MEM_RCU | MEM_ALLOC'. The MEM_ALLOC allows that the per-cpu data can be read and written. Since the memory allocator bpf_mem_alloc() returns a ptr to a percpu ptr for percpu data, the first argument of bpf_this_cpu_ptr() and bpf_per_cpu_ptr() is patched with a dereference before passing to the helper func. Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230827152749.1997202-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Yonghong Song
|
36d8bdf75a |
bpf: Add alloc/xchg/direct_access support for local percpu kptr
Add two new kfunc's, bpf_percpu_obj_new_impl() and
bpf_percpu_obj_drop_impl(), to allocate a percpu obj.
Two functions are very similar to bpf_obj_new_impl()
and bpf_obj_drop_impl(). The major difference is related
to percpu handling.
bpf_rcu_read_lock()
struct val_t __percpu_kptr *v = map_val->percpu_data;
...
bpf_rcu_read_unlock()
For a percpu data map_val like above 'v', the reg->type
is set as
PTR_TO_BTF_ID | MEM_PERCPU | MEM_RCU
if inside rcu critical section.
MEM_RCU marking here is similar to NON_OWN_REF as 'v'
is not a owning reference. But NON_OWN_REF is
trusted and typically inside the spinlock while
MEM_RCU is under rcu read lock. RCU is preferred here
since percpu data structures mean potential concurrent
access into its contents.
Also, bpf_percpu_obj_new_impl() is restricted such that
no pointers or special fields are allowed. Therefore,
the bpf_list_head and bpf_rb_root will not be supported
in this patch set to avoid potential memory leak issue
due to racing between bpf_obj_free_fields() and another
bpf_kptr_xchg() moving an allocated object to
bpf_list_head and bpf_rb_root.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230827152744.1996739-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Dave Marchevsky
|
5861d1e8db |
bpf: Allow bpf_spin_{lock,unlock} in sleepable progs
Commit
|
||
|
Dave Marchevsky
|
0816b8c6bf |
bpf: Consider non-owning refs to refcounted nodes RCU protected
An earlier patch in the series ensures that the underlying memory of nodes with bpf_refcount - which can have multiple owners - is not reused until RCU grace period has elapsed. This prevents use-after-free with non-owning references that may point to recently-freed memory. While RCU read lock is held, it's safe to dereference such a non-owning ref, as by definition RCU GP couldn't have elapsed and therefore underlying memory couldn't have been reused. From the perspective of verifier "trustedness" non-owning refs to refcounted nodes are now trusted only in RCU CS and therefore should no longer pass is_trusted_reg, but rather is_rcu_reg. Let's mark them MEM_RCU in order to reflect this new state. Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> Link: https://lore.kernel.org/r/20230821193311.3290257-6-davemarchevsky@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Dave Marchevsky
|
ba2464c86f |
bpf: Reenable bpf_refcount_acquire
Now that all reported issues are fixed, bpf_refcount_acquire can be turned back on. Also reenable all bpf_refcount-related tests which were disabled. This a revert of: * commit |
||
|
Dave Marchevsky
|
f0d991a070 |
bpf: Ensure kptr_struct_meta is non-NULL for collection insert and refcount_acquire
It's straightforward to prove that kptr_struct_meta must be non-NULL for
any valid call to these kfuncs:
* btf_parse_struct_metas in btf.c creates a btf_struct_meta for any
struct in user BTF with a special field (e.g. bpf_refcount,
{rb,list}_node). These are stored in that BTF's struct_meta_tab.
* __process_kf_arg_ptr_to_graph_node in verifier.c ensures that nodes
have {rb,list}_node field and that it's at the correct offset.
Similarly, check_kfunc_args ensures bpf_refcount field existence for
node param to bpf_refcount_acquire.
* So a btf_struct_meta must have been created for the struct type of
node param to these kfuncs
* That BTF and its struct_meta_tab are guaranteed to still be around.
Any arbitrary {rb,list} node the BPF program interacts with either:
came from bpf_obj_new or a collection removal kfunc in the same
program, in which case the BTF is associated with the program and
still around; or came from bpf_kptr_xchg, in which case the BTF was
associated with the map and is still around
Instead of silently continuing with NULL struct_meta, which caused
confusing bugs such as those addressed by commit
|
||
Yafang Shao
|
d75e30dddf |
bpf: Fix issue in verifying allow_ptr_leaks
After we converted the capabilities of our networking-bpf program from
cap_sys_admin to cap_net_admin+cap_bpf, our networking-bpf program
failed to start. Because it failed the bpf verifier, and the error log
is "R3 pointer comparison prohibited".
A simple reproducer as follows,
SEC("cls-ingress")
int ingress(struct __sk_buff *skb)
{
struct iphdr *iph = (void *)(long)skb->data + sizeof(struct ethhdr);
if ((long)(iph + 1) > (long)skb->data_end)
return TC_ACT_STOLEN;
return TC_ACT_OK;
}
Per discussion with Yonghong and Alexei [1], comparison of two packet
pointers is not a pointer leak. This patch fixes it.
Our local kernel is 6.1.y and we expect this fix to be backported to
6.1.y, so stable is CCed.
[1]. https://lore.kernel.org/bpf/CAADnVQ+Nmspr7Si+pxWn8zkE7hX-7s93ugwC+94aXSy4uQ9vBg@mail.gmail.com/
Suggested-by: Yonghong Song <yonghong.song@linux.dev>
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230823020703.3790-2-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Kumar Kartikeya Dwivedi
|
6785b2edf4 |
bpf: Fix check_func_arg_reg_off bug for graph root/node
The commit being fixed introduced a hunk into check_func_arg_reg_off
that bypasses reg->off == 0 enforcement when offset points to a graph
node or root. This might possibly be done for treating bpf_rbtree_remove
and others as KF_RELEASE and then later check correct reg->off in helper
argument checks.
But this is not the case, those helpers are already not KF_RELEASE and
permit non-zero reg->off and verify it later to match the subobject in
BTF type.
However, this logic leads to bpf_obj_drop permitting free of register
arguments with non-zero offset when they point to a graph root or node
within them, which is not ok.
For instance:
struct foo {
int i;
int j;
struct bpf_rb_node node;
};
struct foo *f = bpf_obj_new(typeof(*f));
if (!f) ...
bpf_obj_drop(f); // OK
bpf_obj_drop(&f->i); // still ok from verifier PoV
bpf_obj_drop(&f->node); // Not OK, but permitted right now
Fix this by dropping the whole part of code altogether.
Fixes:
|
||
|
Yonghong Song
|
ab6c637ad0 |
bpf: Fix a bpf_kptr_xchg() issue with local kptr
When reviewing local percpu kptr support, Alexei discovered a bug
wherea bpf_kptr_xchg() may succeed even if the map value kptr type and
locally allocated obj type do not match ([1]). Missed struct btf_id
comparison is the reason for the bug. This patch added such struct btf_id
comparison and will flag verification failure if types do not match.
[1] https://lore.kernel.org/bpf/20230819002907.io3iphmnuk43xblu@macbook-pro-8.dhcp.thefacebook.com/#t
Reported-by: Alexei Starovoitov <ast@kernel.org>
Fixes:
|
||
|
Yonghong Song
|
db2baf82b0 |
bpf: Fix an incorrect verification success with movsx insn
syzbot reports a verifier bug which triggers a runtime panic.
The test bpf program is:
0: (62) *(u32 *)(r10 -8) = 553656332
1: (bf) r1 = (s16)r10
2: (07) r1 += -8
3: (b7) r2 = 3
4: (bd) if r2 <= r1 goto pc+0
5: (85) call bpf_trace_printk#-138320
6: (b7) r0 = 0
7: (95) exit
At insn 1, the current implementation keeps 'r1' as a frame pointer,
which caused later bpf_trace_printk helper call crash since frame
pointer address is not valid any more. Note that at insn 4,
the 'pointer vs. scalar' comparison is allowed for privileged
prog run.
To fix the problem with above insn 1, the fix in the patch adopts
similar pattern to existing 'R1 = (u32) R2' handling. For unprivileged
prog run, verification will fail with 'R<num> sign-extension part of pointer'.
For privileged prog run, the dst_reg 'r1' will be marked as
an unknown scalar, so later 'bpf_trace_pointk' helper will complain
since it expected certain pointers.
Reported-by: syzbot+d61b595e9205573133b3@syzkaller.appspotmail.com
Fixes:
|
||
|
Jakub Kicinski
|
680ee0456a |
net: invert the netdevice.h vs xdp.h dependency
xdp.h is far more specific and is included in only 67 other files vs netdevice.h's 1538 include sites. Make xdp.h include netdevice.h, instead of the other way around. This decreases the incremental allmodconfig builds size when xdp.h is touched from 5947 to 662 objects. Move bpf_prog_run_xdp() to xdp.h, seems appropriate and filter.h is a mega-header in its own right so it's nice to avoid xdp.h getting included there as well. The only unfortunate part is that the typedef for xdp_features_t has to move to netdevice.h, since its embedded in struct netdevice. Signed-off-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Jesper Dangaard Brouer <hawk@kernel.org> Link: https://lore.kernel.org/r/20230803010230.1755386-4-kuba@kernel.org Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> |
||
|
Yonghong Song
|
09fedc7318 |
bpf: Fix compilation warning with -Wparentheses
The kernel test robot reported compilation warnings when -Wparentheses is
added to KBUILD_CFLAGS with gcc compiler. The following is the error message:
.../bpf-next/kernel/bpf/verifier.c: In function ‘coerce_reg_to_size_sx’:
.../bpf-next/kernel/bpf/verifier.c:5901:14:
error: suggest parentheses around comparison in operand of ‘==’ [-Werror=parentheses]
if (s64_max >= 0 == s64_min >= 0) {
~~~~~~~~^~~~
.../bpf-next/kernel/bpf/verifier.c: In function ‘coerce_subreg_to_size_sx’:
.../bpf-next/kernel/bpf/verifier.c:5965:14:
error: suggest parentheses around comparison in operand of ‘==’ [-Werror=parentheses]
if (s32_min >= 0 == s32_max >= 0) {
~~~~~~~~^~~~
To fix the issue, add proper parentheses for the above '>=' condition
to silence the warning/error.
I tried a few clang compilers like clang16 and clang18 and they do not emit
such warnings with -Wparentheses.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307281133.wi0c4SqG-lkp@intel.com/
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230728055740.2284534-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Yonghong Song
|
4cd58e9af8 |
bpf: Support new 32bit offset jmp instruction
Add interpreter/jit/verifier support for 32bit offset jmp instruction. If a conditional jmp instruction needs more than 16bit offset, it can be simulated with a conditional jmp + a 32bit jmp insn. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230728011231.3716103-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Yonghong Song
|
ec0e2da95f |
bpf: Support new signed div/mod instructions.
Add interpreter/jit support for new signed div/mod insns. The new signed div/mod instructions are encoded with unsigned div/mod instructions plus insn->off == 1. Also add basic verifier support to ensure new insns get accepted. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230728011219.3714605-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Yonghong Song
|
0845c3db7b |
bpf: Support new unconditional bswap instruction
The existing 'be' and 'le' insns will do conditional bswap depends on host endianness. This patch implements unconditional bswap insns. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230728011213.3712808-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Yonghong Song
|
1f1e864b65 |
bpf: Handle sign-extenstin ctx member accesses
Currently, if user accesses a ctx member with signed types, the compiler will generate an unsigned load followed by necessary left and right shifts. With the introduction of sign-extension load, compiler may just emit a ldsx insn instead. Let us do a final movsx sign extension to the final unsigned ctx load result to satisfy original sign extension requirement. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230728011207.3712528-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Yonghong Song
|
8100928c88 |
bpf: Support new sign-extension mov insns
Add interpreter/jit support for new sign-extension mov insns. The original 'MOV' insn is extended to support reg-to-reg signed version for both ALU and ALU64 operations. For ALU mode, the insn->off value of 8 or 16 indicates sign-extension from 8- or 16-bit value to 32-bit value. For ALU64 mode, the insn->off value of 8/16/32 indicates sign-extension from 8-, 16- or 32-bit value to 64-bit value. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230728011202.3712300-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Yonghong Song
|
1f9a1ea821 |
bpf: Support new sign-extension load insns
Add interpreter/jit support for new sign-extension load insns which adds a new mode (BPF_MEMSX). Also add verifier support to recognize these insns and to do proper verification with new insns. In verifier, besides to deduce proper bounds for the dst_reg, probed memory access is also properly handled. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20230728011156.3711870-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Jakub Kicinski
|
59be3baa8d |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Cross-merge networking fixes after downstream PR. No conflicts or adjacent changes. Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
||
Anton Protopopov
|
5ba190c29c |
bpf: consider CONST_PTR_TO_MAP as trusted pointer to struct bpf_map
Add the BTF id of struct bpf_map to the reg2btf_ids array. This makes the values of the CONST_PTR_TO_MAP type to be considered as trusted by kfuncs. This, in turn, allows users to execute trusted kfuncs which accept `struct bpf_map *` arguments from non-tracing programs. While exporting the btf_bpf_map_id variable, save some bytes by defining it as BTF_ID_LIST_GLOBAL_SINGLE (which is u32[1]) and not as BTF_ID_LIST (which is u32[64]). Signed-off-by: Anton Protopopov <aspsk@isovalent.com> Link: https://lore.kernel.org/r/20230719092952.41202-3-aspsk@isovalent.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Anton Protopopov
|
831deb2976 |
bpf: consider types listed in reg2btf_ids as trusted
The reg2btf_ids array contains a list of types for which we can (and need) to find a corresponding static BTF id. All the types in the list can be considered as trusted for purposes of kfuncs. Signed-off-by: Anton Protopopov <aspsk@isovalent.com> Link: https://lore.kernel.org/r/20230719092952.41202-2-aspsk@isovalent.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
b5e9ad522c |
bpf: Repeat check_max_stack_depth for async callbacks
While the check_max_stack_depth function explores call chains emanating
from the main prog, which is typically enough to cover all possible call
chains, it doesn't explore those rooted at async callbacks unless the
async callback will have been directly called, since unlike non-async
callbacks it skips their instruction exploration as they don't
contribute to stack depth.
It could be the case that the async callback leads to a callchain which
exceeds the stack depth, but this is never reachable while only
exploring the entry point from main subprog. Hence, repeat the check for
the main subprog *and* all async callbacks marked by the symbolic
execution pass of the verifier, as execution of the program may begin at
any of them.
Consider functions with following stack depths:
main: 256
async: 256
foo: 256
main:
rX = async
bpf_timer_set_callback(...)
async:
foo()
Here, async is not descended as it does not contribute to stack depth of
main (since it is referenced using bpf_pseudo_func and not
bpf_pseudo_call). However, when async is invoked asynchronously, it will
end up breaching the MAX_BPF_STACK limit by calling foo.
Hence, in addition to main, we also need to explore call chains
beginning at all async callback subprogs in a program.
Fixes:
|
||
|
Kumar Kartikeya Dwivedi
|
ba7b3e7d5f |
bpf: Fix subprog idx logic in check_max_stack_depth
The assignment to idx in check_max_stack_depth happens once we see a
bpf_pseudo_call or bpf_pseudo_func. This is not an issue as the rest of
the code performs a few checks and then pushes the frame to the frame
stack, except the case of async callbacks. If the async callback case
causes the loop iteration to be skipped, the idx assignment will be
incorrect on the next iteration of the loop. The value stored in the
frame stack (as the subprogno of the current subprog) will be incorrect.
This leads to incorrect checks and incorrect tail_call_reachable
marking. Save the target subprog in a new variable and only assign to
idx once we are done with the is_async_cb check which may skip pushing
of frame to the frame stack and subsequent stack depth checks and tail
call markings.
Fixes:
|
||
|
Jakub Kicinski
|
d2afa89f66 |
for-netdev
-----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEE+soXsSLHKoYyzcli6rmadz2vbToFAmSwqwoACgkQ6rmadz2v bTqOHRAAn+fzTLqUqsveFQcxOkie5MPHxKoOTjG4+yFR7rzPkU6Mn5RX3w5yFzSn RqutwykF9OgipAzC3QXv4pRJuq6Gia5nvwUSDP4CX273ljyeF54DK7HfopE1+YrK HXyBWZvVvMZP6q7qQyQ3qtbHZSjs5XP/M6YBlJ5zo/BTLFCyvbSDP14YKEqcBkWG ld72ElXFxlnr/zEfRjzBCfMlbmgeHLO0SiHS/9827zEmNP1AAH5/ETA7/rJ7yCJs QNQUIoJWob8xm5FMJ6CU/+sOqXR1CY053meGJFFBX5pvVD/CLRhrwHn0IMCyQqmh wKR5waeXhpl/CKNeFuxXVMNFiXbqBb/0LYJaJtrMysjMLTsQ9X7NkrDBa/+kYGyZ +ghGlaMQvPqUGg0rLH2nl9JNB8Ne/8prLMsAKUWnPuOo+Q03j054gnqhGeNtDd5b gpSk+7x93PlhGcegBV1Wk8dkiGC5V9nTVNxg40XQUCs4k9L/8Vjc35Tjqx7nBTNH DiFD24DDKUZacw9L6nEqvLF/N2fiRjtUZnVPC0yn/annyBcfX1s+ZH2Tu1F6Qk38 QMfBCnt12exmsiDoxdzzGJtjHnS/k5fsaKjlR21mOyMrIH7ipltr5UHHrdr1hBP6 24uSeTImvQQKDi+9IuXN127jZDOupKqVS6csrA0ZXrlKWh2HR+U= =GVUB -----END PGP SIGNATURE----- Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next Alexei Starovoitov says: ==================== pull-request: bpf-next 2023-07-13 We've added 67 non-merge commits during the last 15 day(s) which contain a total of 106 files changed, 4444 insertions(+), 619 deletions(-). The main changes are: 1) Fix bpftool build in presence of stale vmlinux.h, from Alexander Lobakin. 2) Introduce bpf_me_mcache_free_rcu() and fix OOM under stress, from Alexei Starovoitov. 3) Teach verifier actual bounds of bpf_get_smp_processor_id() and fix perf+libbpf issue related to custom section handling, from Andrii Nakryiko. 4) Introduce bpf map element count, from Anton Protopopov. 5) Check skb ownership against full socket, from Kui-Feng Lee. 6) Support for up to 12 arguments in BPF trampoline, from Menglong Dong. 7) Export rcu_request_urgent_qs_task, from Paul E. McKenney. 8) Fix BTF walking of unions, from Yafang Shao. 9) Extend link_info for kprobe_multi and perf_event links, from Yafang Shao. * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (67 commits) selftests/bpf: Add selftest for PTR_UNTRUSTED bpf: Fix an error in verifying a field in a union selftests/bpf: Add selftests for nested_trust bpf: Fix an error around PTR_UNTRUSTED selftests/bpf: add testcase for TRACING with 6+ arguments bpf, x86: allow function arguments up to 12 for TRACING bpf, x86: save/restore regs with BPF_DW size bpftool: Use "fallthrough;" keyword instead of comments bpf: Add object leak check. bpf: Convert bpf_cpumask to bpf_mem_cache_free_rcu. bpf: Introduce bpf_mem_free_rcu() similar to kfree_rcu(). selftests/bpf: Improve test coverage of bpf_mem_alloc. rcu: Export rcu_request_urgent_qs_task() bpf: Allow reuse from waiting_for_gp_ttrace list. bpf: Add a hint to allocated objects. bpf: Change bpf_mem_cache draining process. bpf: Further refactor alloc_bulk(). bpf: Factor out inc/dec of active flag into helpers. bpf: Refactor alloc_bulk(). bpf: Let free_all() return the number of freed elements. ... ==================== Link: https://lore.kernel.org/r/20230714020910.80794-1-alexei.starovoitov@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
||
|
Yafang Shao
|
7ce4dc3e4a |
bpf: Fix an error around PTR_UNTRUSTED
Per discussion with Alexei, the PTR_UNTRUSTED flag should not been
cleared when we start to walk a new struct, because the struct in
question may be a struct nested in a union. We should also check and set
this flag before we walk its each member, in case itself is a union.
We will clear this flag if the field is BTF_TYPE_SAFE_RCU_OR_NULL.
Fixes:
|
||
|
Andrii Nakryiko
|
f42bcd168d |
bpf: teach verifier actual bounds of bpf_get_smp_processor_id() result
bpf_get_smp_processor_id() helper returns current CPU on which BPF program runs. It can't return value that is bigger than maximum allowed number of CPUs (minus one, due to zero indexing). Teach BPF verifier to recognize that. This makes it possible to use bpf_get_smp_processor_id() result to index into arrays without extra checks, as demonstrated in subsequent selftests/bpf patch. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230711232400.1658562-1-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Kumar Kartikeya Dwivedi
|
5415ccd50a |
bpf: Fix max stack depth check for async callbacks
The check_max_stack_depth pass happens after the verifier's symbolic
execution, and attempts to walk the call graph of the BPF program,
ensuring that the stack usage stays within bounds for all possible call
chains. There are two cases to consider: bpf_pseudo_func and
bpf_pseudo_call. In the former case, the callback pointer is loaded into
a register, and is assumed that it is passed to some helper later which
calls it (however there is no way to be sure), but the check remains
conservative and accounts the stack usage anyway. For this particular
case, asynchronous callbacks are skipped as they execute asynchronously
when their corresponding event fires.
The case of bpf_pseudo_call is simpler and we know that the call is
definitely made, hence the stack depth of the subprog is accounted for.
However, the current check still skips an asynchronous callback even if
a bpf_pseudo_call was made for it. This is erroneous, as it will miss
accounting for the stack usage of the asynchronous callback, which can
be used to breach the maximum stack depth limit.
Fix this by only skipping asynchronous callbacks when the instruction is
not a pseudo call to the subprog.
Fixes:
|
||
|
Jakub Kicinski
|
a685d0df75 |
bpf-next-for-netdev
-----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQTFp0I1jqZrAX+hPRXbK58LschIgwUCZJX+ygAKCRDbK58LschI g0/2AQDHg12smf9mPfK9wOFDNRIIX8r2iufB8LUFQMzCwltN6gEAkAdkAyfbof7P TMaNUiHABijAFtChxoSI35j3OOSRrwE= =GJgN -----END PGP SIGNATURE----- Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next Daniel Borkmann says: ==================== pull-request: bpf-next 2023-06-23 We've added 49 non-merge commits during the last 24 day(s) which contain a total of 70 files changed, 1935 insertions(+), 442 deletions(-). The main changes are: 1) Extend bpf_fib_lookup helper to allow passing the route table ID, from Louis DeLosSantos. 2) Fix regsafe() in verifier to call check_ids() for scalar registers, from Eduard Zingerman. 3) Extend the set of cpumask kfuncs with bpf_cpumask_first_and() and a rework of bpf_cpumask_any*() kfuncs. Additionally, add selftests, from David Vernet. 4) Fix socket lookup BPF helpers for tc/XDP to respect VRF bindings, from Gilad Sever. 5) Change bpf_link_put() to use workqueue unconditionally to fix it under PREEMPT_RT, from Sebastian Andrzej Siewior. 6) Follow-ups to address issues in the bpf_refcount shared ownership implementation, from Dave Marchevsky. 7) A few general refactorings to BPF map and program creation permissions checks which were part of the BPF token series, from Andrii Nakryiko. 8) Various fixes for benchmark framework and add a new benchmark for BPF memory allocator to BPF selftests, from Hou Tao. 9) Documentation improvements around iterators and trusted pointers, from Anton Protopopov. 10) Small cleanup in verifier to improve allocated object check, from Daniel T. Lee. 11) Improve performance of bpf_xdp_pointer() by avoiding access to shared_info when XDP packet does not have frags, from Jesper Dangaard Brouer. 12) Silence a harmless syzbot-reported warning in btf_type_id_size(), from Yonghong Song. 13) Remove duplicate bpfilter_umh_cleanup in favor of umd_cleanup_helper, from Jarkko Sakkinen. 14) Fix BPF selftests build for resolve_btfids under custom HOSTCFLAGS, from Viktor Malik. * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (49 commits) bpf, docs: Document existing macros instead of deprecated bpf, docs: BPF Iterator Document selftests/bpf: Fix compilation failure for prog vrf_socket_lookup selftests/bpf: Add vrf_socket_lookup tests bpf: Fix bpf socket lookup from tc/xdp to respect socket VRF bindings bpf: Call __bpf_sk_lookup()/__bpf_skc_lookup() directly via TC hookpoint bpf: Factor out socket lookup functions for the TC hookpoint. selftests/bpf: Set the default value of consumer_cnt as 0 selftests/bpf: Ensure that next_cpu() returns a valid CPU number selftests/bpf: Output the correct error code for pthread APIs selftests/bpf: Use producer_cnt to allocate local counter array xsk: Remove unused inline function xsk_buff_discard() bpf: Keep BPF_PROG_LOAD permission checks clear of validations bpf: Centralize permissions checks for all BPF map types bpf: Inline map creation logic in map_create() function bpf: Move unprivileged checks into map_create() and bpf_prog_load() bpf: Remove in_atomic() from bpf_link_put(). selftests/bpf: Verify that check_ids() is used for scalars in regsafe() bpf: Verify scalar ids mapping in regsafe() using check_ids() selftests/bpf: Check if mark_chain_precision() follows scalar ids ... ==================== Link: https://lore.kernel.org/r/20230623211256.8409-1-daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
||
|
Jakub Kicinski
|
a7384f3918 |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Cross-merge networking fixes after downstream PR. Conflicts: tools/testing/selftests/net/fcnal-test.sh |
||
|
Eduard Zingerman
|
1ffc85d929 |
bpf: Verify scalar ids mapping in regsafe() using check_ids()
Make sure that the following unsafe example is rejected by verifier:
1: r9 = ... some pointer with range X ...
2: r6 = ... unbound scalar ID=a ...
3: r7 = ... unbound scalar ID=b ...
4: if (r6 > r7) goto +1
5: r6 = r7
6: if (r6 > X) goto ...
--- checkpoint ---
7: r9 += r7
8: *(u64 *)r9 = Y
This example is unsafe because not all execution paths verify r7 range.
Because of the jump at (4) the verifier would arrive at (6) in two states:
I. r6{.id=b}, r7{.id=b} via path 1-6;
II. r6{.id=a}, r7{.id=b} via path 1-4, 6.
Currently regsafe() does not call check_ids() for scalar registers,
thus from POV of regsafe() states (I) and (II) are identical. If the
path 1-6 is taken by verifier first, and checkpoint is created at (6)
the path [1-4, 6] would be considered safe.
Changes in this commit:
- check_ids() is modified to disallow mapping multiple old_id to the
same cur_id.
- check_scalar_ids() is added, unlike check_ids() it treats ID zero as
a unique scalar ID.
- check_scalar_ids() needs to generate temporary unique IDs, field
'tmp_id_gen' is added to bpf_verifier_env::idmap_scratch to
facilitate this.
- regsafe() is updated to:
- use check_scalar_ids() for precise scalar registers.
- compare scalar registers using memcmp only for explore_alu_limits
branch. This simplifies control flow for scalar case, and has no
measurable performance impact.
- check_alu_op() is updated to avoid generating bpf_reg_state::id for
constant scalar values when processing BPF_MOV. ID is needed to
propagate range information for identical values, but there is
nothing to propagate for constants.
Fixes:
|
||
|
Eduard Zingerman
|
904e6ddf41 |
bpf: Use scalar ids in mark_chain_precision()
Change mark_chain_precision() to track precision in situations
like below:
r2 = unknown value
...
--- state #0 ---
...
r1 = r2 // r1 and r2 now share the same ID
...
--- state #1 {r1.id = A, r2.id = A} ---
...
if (r2 > 10) goto exit; // find_equal_scalars() assigns range to r1
...
--- state #2 {r1.id = A, r2.id = A} ---
r3 = r10
r3 += r1 // need to mark both r1 and r2
At the beginning of the processing of each state, ensure that if a
register with a scalar ID is marked as precise, all registers sharing
this ID are also marked as precise.
This property would be used by a follow-up change in regsafe().
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230613153824.3324830-2-eddyz87@gmail.com
|
||
Krister Johansen
|
0108a4e9f3 |
bpf: ensure main program has an extable
When subprograms are in use, the main program is not jit'd after the
subprograms because jit_subprogs sets a value for prog->bpf_func upon
success. Subsequent calls to the JIT are bypassed when this value is
non-NULL. This leads to a situation where the main program and its
func[0] counterpart are both in the bpf kallsyms tree, but only func[0]
has an extable. Extables are only created during JIT. Now there are
two nearly identical program ksym entries in the tree, but only one has
an extable. Depending upon how the entries are placed, there's a chance
that a fault will call search_extable on the aux with the NULL entry.
Since jit_subprogs already copies state from func[0] to the main
program, include the extable pointer in this state duplication.
Additionally, ensure that the copy of the main program in func[0] is not
added to the bpf_prog_kallsyms table. Instead, let the main program get
added later in bpf_prog_load(). This ensures there is only a single
copy of the main program in the kallsyms table, and that its tag matches
the tag observed by tooling like bpftool.
Cc: stable@vger.kernel.org
Fixes:
|
||
Maxim Mikityanskiy
|
713274f1f2 |
bpf: Fix verifier id tracking of scalars on spill
The following scenario describes a bug in the verifier where it
incorrectly concludes about equivalent scalar IDs which could lead to
verifier bypass in privileged mode:
1. Prepare a 32-bit rogue number.
2. Put the rogue number into the upper half of a 64-bit register, and
roll a random (unknown to the verifier) bit in the lower half. The
rest of the bits should be zero (although variations are possible).
3. Assign an ID to the register by MOVing it to another arbitrary
register.
4. Perform a 32-bit spill of the register, then perform a 32-bit fill to
another register. Due to a bug in the verifier, the ID will be
preserved, although the new register will contain only the lower 32
bits, i.e. all zeros except one random bit.
At this point there are two registers with different values but the same
ID, which means the integrity of the verifier state has been corrupted.
5. Compare the new 32-bit register with 0. In the branch where it's
equal to 0, the verifier will believe that the original 64-bit
register is also 0, because it has the same ID, but its actual value
still contains the rogue number in the upper half.
Some optimizations of the verifier prevent the actual bypass, so
extra care is needed: the comparison must be between two registers,
and both branches must be reachable (this is why one random bit is
needed). Both branches are still suitable for the bypass.
6. Right shift the original register by 32 bits to pop the rogue number.
7. Use the rogue number as an offset with any pointer. The verifier will
believe that the offset is 0, while in reality it's the given number.
The fix is similar to the 32-bit BPF_MOV handling in check_alu_op for
SCALAR_VALUE. If the spill is narrowing the actual register value, don't
keep the ID, make sure it's reset to 0.
Fixes:
|
||
|
David Vernet
|
51302c951c |
bpf: Teach verifier that trusted PTR_TO_BTF_ID pointers are non-NULL
In reg_type_not_null(), we currently assume that a pointer may be NULL
if it has the PTR_MAYBE_NULL modifier, or if it doesn't belong to one of
several base type of pointers that are never NULL-able. For example,
PTR_TO_CTX, PTR_TO_MAP_VALUE, etc.
It turns out that in some cases, PTR_TO_BTF_ID can never be NULL as
well, though we currently don't specify it. For example, if you had the
following program:
SEC("tc")
long example_refcnt_fail(void *ctx)
{
struct bpf_cpumask *mask1, *mask2;
mask1 = bpf_cpumask_create();
mask2 = bpf_cpumask_create();
if (!mask1 || !mask2)
goto error_release;
bpf_cpumask_test_cpu(0, (const struct cpumask *)mask1);
bpf_cpumask_test_cpu(0, (const struct cpumask *)mask2);
error_release:
if (mask1)
bpf_cpumask_release(mask1);
if (mask2)
bpf_cpumask_release(mask2);
return ret;
}
The verifier will incorrectly fail to load the program, thinking
(unintuitively) that we have a possibly-unreleased reference if the mask
is NULL, because we (correctly) don't issue a bpf_cpumask_release() on
the NULL path.
The reason the verifier gets confused is due to the fact that we don't
explicitly tell the verifier that trusted PTR_TO_BTF_ID pointers can
never be NULL. Basically, if we successfully get past the if check
(meaning both pointers go from ptr_or_null_bpf_cpumask to
ptr_bpf_cpumask), the verifier will correctly assume that the references
need to be dropped on any possible branch that leads to program exit.
However, it will _incorrectly_ think that the ptr == NULL branch is
possible, and will erroneously detect it as a branch on which we failed
to drop the reference.
The solution is of course to teach the verifier that trusted
PTR_TO_BTF_ID pointers can never be NULL, so that it doesn't incorrectly
think it's possible for the reference to be present on the ptr == NULL
branch.
A follow-on patch will add a selftest that verifies this behavior.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230602150112.1494194-1-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
Daniel T. Lee
|
503e4def54 |
bpf: Replace open code with for allocated object check
>From commit |
||
|
Dave Marchevsky
|
7793fc3bab |
bpf: Make bpf_refcount_acquire fallible for non-owning refs
This patch fixes an incorrect assumption made in the original
bpf_refcount series [0], specifically that the BPF program calling
bpf_refcount_acquire on some node can always guarantee that the node is
alive. In that series, the patch adding failure behavior to rbtree_add
and list_push_{front, back} breaks this assumption for non-owning
references.
Consider the following program:
n = bpf_kptr_xchg(&mapval, NULL);
/* skip error checking */
bpf_spin_lock(&l);
if(bpf_rbtree_add(&t, &n->rb, less)) {
bpf_refcount_acquire(n);
/* Failed to add, do something else with the node */
}
bpf_spin_unlock(&l);
It's incorrect to assume that bpf_refcount_acquire will always succeed in this
scenario. bpf_refcount_acquire is being called in a critical section
here, but the lock being held is associated with rbtree t, which isn't
necessarily the lock associated with the tree that the node is already
in. So after bpf_rbtree_add fails to add the node and calls bpf_obj_drop
in it, the program has no ownership of the node's lifetime. Therefore
the node's refcount can be decr'd to 0 at any time after the failing
rbtree_add. If this happens before the refcount_acquire above, the node
might be free'd, and regardless refcount_acquire will be incrementing a
0 refcount.
Later patches in the series exercise this scenario, resulting in the
expected complaint from the kernel (without this patch's changes):
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 207 at lib/refcount.c:25 refcount_warn_saturate+0xbc/0x110
Modules linked in: bpf_testmod(O)
CPU: 1 PID: 207 Comm: test_progs Tainted: G O 6.3.0-rc7-02231-g723de1a718a2-dirty #371
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014
RIP: 0010:refcount_warn_saturate+0xbc/0x110
Code: 6f 64 f6 02 01 e8 84 a3 5c ff 0f 0b eb 9d 80 3d 5e 64 f6 02 00 75 94 48 c7 c7 e0 13 d2 82 c6 05 4e 64 f6 02 01 e8 64 a3 5c ff <0f> 0b e9 7a ff ff ff 80 3d 38 64 f6 02 00 0f 85 6d ff ff ff 48 c7
RSP: 0018:ffff88810b9179b0 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000
RDX: 0000000000000202 RSI: 0000000000000008 RDI: ffffffff857c3680
RBP: ffff88810027d3c0 R08: ffffffff8125f2a4 R09: ffff88810b9176e7
R10: ffffed1021722edc R11: 746e756f63666572 R12: ffff88810027d388
R13: ffff88810027d3c0 R14: ffffc900005fe030 R15: ffffc900005fe048
FS: 00007fee0584a700(0000) GS:ffff88811b280000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005634a96f6c58 CR3: 0000000108ce9002 CR4: 0000000000770ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<TASK>
bpf_refcount_acquire_impl+0xb5/0xc0
(rest of output snipped)
The patch addresses this by changing bpf_refcount_acquire_impl to use
refcount_inc_not_zero instead of refcount_inc and marking
bpf_refcount_acquire KF_RET_NULL.
For owning references, though, we know the above scenario is not possible
and thus that bpf_refcount_acquire will always succeed. Some verifier
bookkeeping is added to track "is input owning ref?" for bpf_refcount_acquire
calls and return false from is_kfunc_ret_null for bpf_refcount_acquire on
owning refs despite it being marked KF_RET_NULL.
Existing selftests using bpf_refcount_acquire are modified where
necessary to NULL-check its return value.
[0]: https://lore.kernel.org/bpf/20230415201811.343116-1-davemarchevsky@fb.com/
Fixes:
|
||
|
Dave Marchevsky
|
2140a6e342 |
bpf: Set kptr_struct_meta for node param to list and rbtree insert funcs
In verifier.c, fixup_kfunc_call uses struct bpf_insn_aux_data's
kptr_struct_meta field to pass information about local kptr types to
various helpers and kfuncs at runtime. The recent bpf_refcount series
added a few functions to the set that need this information:
* bpf_refcount_acquire
* Needs to know where the refcount field is in order to increment
* Graph collection insert kfuncs: bpf_rbtree_add, bpf_list_push_{front,back}
* Were migrated to possibly fail by the bpf_refcount series. If
insert fails, the input node is bpf_obj_drop'd. bpf_obj_drop needs
the kptr_struct_meta in order to decr refcount and properly free
special fields.
Unfortunately the verifier handling of collection insert kfuncs was not
modified to actually populate kptr_struct_meta. Accordingly, when the
node input to those kfuncs is passed to bpf_obj_drop, it is done so
without the information necessary to decr refcount.
This patch fixes the issue by populating kptr_struct_meta for those
kfuncs.
Fixes:
|
||
|
Jakub Kicinski
|
75455b906d |
bpf-next-for-netdev
-----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQTFp0I1jqZrAX+hPRXbK58LschIgwUCZHEm+wAKCRDbK58LschI gyIKAQCqO7B4sIu8hYVxBTwfHV2tIuXSMSCV4P9e78NUOPcO2QEAvLP/WVSjB0Bm vpyTKKM22SpZvPe/jSp52j6t20N+qAc= =HFxD -----END PGP SIGNATURE----- Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next Daniel Borkmann says: ==================== pull-request: bpf-next 2023-05-26 We've added 54 non-merge commits during the last 10 day(s) which contain a total of 76 files changed, 2729 insertions(+), 1003 deletions(-). The main changes are: 1) Add the capability to destroy sockets in BPF through a new kfunc, from Aditi Ghag. 2) Support O_PATH fds in BPF_OBJ_PIN and BPF_OBJ_GET commands, from Andrii Nakryiko. 3) Add capability for libbpf to resize datasec maps when backed via mmap, from JP Kobryn. 4) Move all the test kfuncs for CI out of the kernel and into bpf_testmod, from Jiri Olsa. 5) Big batch of xsk selftest improvements to prep for multi-buffer testing, from Magnus Karlsson. 6) Show the target_{obj,btf}_id in tracing link's fdinfo and dump it via bpftool, from Yafang Shao. 7) Various misc BPF selftest improvements to work with upcoming LLVM 17, from Yonghong Song. 8) Extend bpftool to specify netdevice for resolving XDP hints, from Larysa Zaremba. 9) Document masking in shift operations for the insn set document, from Dave Thaler. 10) Extend BPF selftests to check xdp_feature support for bond driver, from Lorenzo Bianconi. * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (54 commits) bpf: Fix bad unlock balance on freeze_mutex libbpf: Ensure FD >= 3 during bpf_map__reuse_fd() libbpf: Ensure libbpf always opens files with O_CLOEXEC selftests/bpf: Check whether to run selftest libbpf: Change var type in datasec resize func bpf: drop unnecessary bpf_capable() check in BPF_MAP_FREEZE command libbpf: Selftests for resizing datasec maps libbpf: Add capability for resizing datasec maps selftests/bpf: Add path_fd-based BPF_OBJ_PIN and BPF_OBJ_GET tests libbpf: Add opts-based bpf_obj_pin() API and add support for path_fd bpf: Support O_PATH FDs in BPF_OBJ_PIN and BPF_OBJ_GET commands libbpf: Start v1.3 development cycle bpf: Validate BPF object in BPF_OBJ_PIN before calling LSM bpftool: Specify XDP Hints ifname when loading program selftests/bpf: Add xdp_feature selftest for bond device selftests/bpf: Test bpf_sock_destroy selftests/bpf: Add helper to get port using getsockname bpf: Add bpf_sock_destroy kfunc bpf: Add kfunc filter function to 'struct btf_kfunc_id_set' bpf: udp: Implement batching for sockets iterator ... ==================== Link: https://lore.kernel.org/r/20230526222747.17775-1-daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
||
|
Jakub Kicinski
|
d4031ec844 |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Cross-merge networking fixes after downstream PR. Conflicts: net/ipv4/raw.c |
||
Aditi Ghag
|
e924e80ee6 |
bpf: Add kfunc filter function to 'struct btf_kfunc_id_set'
This commit adds the ability to filter kfuncs to certain BPF program types. This is required to limit bpf_sock_destroy kfunc implemented in follow-up commits to programs with attach type 'BPF_TRACE_ITER'. The commit adds a callback filter to 'struct btf_kfunc_id_set'. The filter has access to the `bpf_prog` construct including its properties such as `expected_attached_type`. Signed-off-by: Aditi Ghag <aditi.ghag@isovalent.com> Link: https://lore.kernel.org/r/20230519225157.760788-7-aditi.ghag@isovalent.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> |
||
Will Deacon
|
0613d8ca9a |
bpf: Fix mask generation for 32-bit narrow loads of 64-bit fields
A narrow load from a 64-bit context field results in a 64-bit load
followed potentially by a 64-bit right-shift and then a bitwise AND
operation to extract the relevant data.
In the case of a 32-bit access, an immediate mask of 0xffffffff is used
to construct a 64-bit BPP_AND operation which then sign-extends the mask
value and effectively acts as a glorified no-op. For example:
0: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0)
results in the following code generation for a 64-bit field:
ldr x7, [x7] // 64-bit load
mov x10, #0xffffffffffffffff
and x7, x7, x10
Fix the mask generation so that narrow loads always perform a 32-bit AND
operation:
ldr x7, [x7] // 64-bit load
mov w10, #0xffffffff
and w7, w7, w10
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Krzesimir Nowak <krzesimir@kinvolk.io>
Cc: Andrey Ignatov <rdna@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Fixes:
|
||
|
Andrii Nakryiko
|
d84b1a6708 |
bpf: fix calculation of subseq_idx during precision backtracking
Subsequent instruction index (subseq_idx) is an index of an instruction
that was verified/executed by verifier after the currently processed
instruction. It is maintained during precision backtracking processing
and is used to detect various subprog calling conditions.
This patch fixes the bug with incorrectly resetting subseq_idx to -1
when going from child state to parent state during backtracking. If we
don't maintain correct subseq_idx we can misidentify subprog calls
leading to precision tracking bugs.
One such case was triggered by test_global_funcs/global_func9 test where
global subprog call happened to be the very last instruction in parent
state, leading to subseq_idx==-1, triggering WARN_ONCE:
[ 36.045754] verifier backtracking bug
[ 36.045764] WARNING: CPU: 13 PID: 2073 at kernel/bpf/verifier.c:3503 __mark_chain_precision+0xcc6/0xde0
[ 36.046819] Modules linked in: aesni_intel(E) crypto_simd(E) cryptd(E) kvm_intel(E) kvm(E) irqbypass(E) i2c_piix4(E) serio_raw(E) i2c_core(E) crc32c_intel)
[ 36.048040] CPU: 13 PID: 2073 Comm: test_progs Tainted: G W OE 6.3.0-07976-g4d585f48ee6b-dirty #972
[ 36.048783] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
[ 36.049648] RIP: 0010:__mark_chain_precision+0xcc6/0xde0
[ 36.050038] Code: 3d 82 c6 05 bb 35 32 02 01 e8 66 21 ec ff 0f 0b b8 f2 ff ff ff e9 30 f5 ff ff 48 c7 c7 f3 61 3d 82 4c 89 0c 24 e8 4a 21 ec ff <0f> 0b 4c0
With the fix precision tracking across multiple states works correctly now:
mark_precise: frame0: last_idx 45 first_idx 38 subseq_idx -1
mark_precise: frame0: regs=r8 stack= before 44: (61) r7 = *(u32 *)(r10 -4)
mark_precise: frame0: regs=r8 stack= before 43: (85) call pc+41
mark_precise: frame0: regs=r8 stack= before 42: (07) r1 += -48
mark_precise: frame0: regs=r8 stack= before 41: (bf) r1 = r10
mark_precise: frame0: regs=r8 stack= before 40: (63) *(u32 *)(r10 -48) = r1
mark_precise: frame0: regs=r8 stack= before 39: (b4) w1 = 0
mark_precise: frame0: regs=r8 stack= before 38: (85) call pc+38
mark_precise: frame0: parent state regs=r8 stack=: R0_w=scalar() R1_w=map_value(off=4,ks=4,vs=8,imm=0) R6=1 R7_w=scalar() R8_r=P0 R10=fpm
mark_precise: frame0: last_idx 36 first_idx 28 subseq_idx 38
mark_precise: frame0: regs=r8 stack= before 36: (18) r1 = 0xffff888104f2ed14
mark_precise: frame0: regs=r8 stack= before 35: (85) call pc+33
mark_precise: frame0: regs=r8 stack= before 33: (18) r1 = 0xffff888104f2ed10
mark_precise: frame0: regs=r8 stack= before 32: (85) call pc+36
mark_precise: frame0: regs=r8 stack= before 31: (07) r1 += -4
mark_precise: frame0: regs=r8 stack= before 30: (bf) r1 = r10
mark_precise: frame0: regs=r8 stack= before 29: (63) *(u32 *)(r10 -4) = r7
mark_precise: frame0: regs=r8 stack= before 28: (4c) w7 |= w0
mark_precise: frame0: parent state regs=r8 stack=: R0_rw=scalar() R6=1 R7_rw=scalar() R8_rw=P0 R10=fp0 fp-48_r=mmmmmmmm
mark_precise: frame0: last_idx 27 first_idx 16 subseq_idx 28
mark_precise: frame0: regs=r8 stack= before 27: (85) call pc+31
mark_precise: frame0: regs=r8 stack= before 26: (b7) r1 = 0
mark_precise: frame0: regs=r8 stack= before 25: (b7) r8 = 0
Note how subseq_idx starts out as -1, then is preserved as 38 and then 28 as we
go up the parent state chain.
Reported-by: Alexei Starovoitov <ast@kernel.org>
Fixes:
|
||
|
Dave Marchevsky
|
4d585f48ee |
bpf: Remove anonymous union in bpf_kfunc_call_arg_meta
For kfuncs like bpf_obj_drop and bpf_refcount_acquire - which take
user-defined types as input - the verifier needs to track the specific
type passed in when checking a particular kfunc call. This requires
tracking (btf, btf_id) tuple. In commit
|
||
Daniel Rosenberg
|
2012c867c8 |
bpf: verifier: Accept dynptr mem as mem in helpers
This allows using memory retrieved from dynptrs with helper functions that accept ARG_PTR_TO_MEM. For instance, results from bpf_dynptr_data can be passed along to bpf_strncmp. Signed-off-by: Daniel Rosenberg <drosen@google.com> Link: https://lore.kernel.org/r/20230506013134.2492210-5-drosen@google.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Daniel Rosenberg
|
3bda08b636 |
bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)
bpf_dynptr_slice(_rw) uses a user provided buffer if it can not provide a pointer to a block of contiguous memory. This buffer is unused in the case of local dynptrs, and may be unused in other cases as well. There is no need to require the buffer, as the kfunc can just return NULL if it was needed and not provided. This adds another kfunc annotation, __opt, which combines with __sz and __szk to allow the buffer associated with the size to be NULL. If the buffer is NULL, the verifier does not check that the buffer is of sufficient size. Signed-off-by: Daniel Rosenberg <drosen@google.com> Link: https://lore.kernel.org/r/20230506013134.2492210-2-drosen@google.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Andrii Nakryiko
|
fde2a3882b |
bpf: support precision propagation in the presence of subprogs
Add support precision backtracking in the presence of subprogram frames in
jump history.
This means supporting a few different kinds of subprogram invocation
situations, all requiring a slightly different handling in precision
backtracking handling logic:
- static subprogram calls;
- global subprogram calls;
- callback-calling helpers/kfuncs.
For each of those we need to handle a few precision propagation cases:
- what to do with precision of subprog returns (r0);
- what to do with precision of input arguments;
- for all of them callee-saved registers in caller function should be
propagated ignoring subprog/callback part of jump history.
N.B. Async callback-calling helpers (currently only
bpf_timer_set_callback()) are transparent to all this because they set
a separate async callback environment and thus callback's history is not
shared with main program's history. So as far as all the changes in this
commit goes, such helper is just a regular helper.
Let's look at all these situation in more details. Let's start with
static subprogram being called, using an exxerpt of a simple main
program and its static subprog, indenting subprog's frame slightly to
make everything clear.
frame 0 frame 1 precision set
======= ======= =============
9: r6 = 456;
10: r1 = 123; fr0: r6
11: call pc+10; fr0: r1, r6
22: r0 = r1; fr0: r6; fr1: r1
23: exit fr0: r6; fr1: r0
12: r1 = <map_pointer> fr0: r0, r6
13: r1 += r0; fr0: r0, r6
14: r1 += r6; fr0: r6
15: exit
As can be seen above main function is passing 123 as single argument to
an identity (`return x;`) subprog. Returned value is used to adjust map
pointer offset, which forces r0 to be marked as precise. Then
instruction #14 does the same for callee-saved r6, which will have to be
backtracked all the way to instruction #9. For brevity, precision sets
for instruction #13 and #14 are combined in the diagram above.
First, for subprog calls, r0 returned from subprog (in frame 0) has to
go into subprog's frame 1, and should be cleared from frame 0. So we go
back into subprog's frame knowing we need to mark r0 precise. We then
see that insn #22 sets r0 from r1, so now we care about marking r1
precise. When we pop up from subprog's frame back into caller at
insn #11 we keep r1, as it's an argument-passing register, so we eventually
find `10: r1 = 123;` and satify precision propagation chain for insn #13.
This example demonstrates two sets of rules:
- r0 returned after subprog call has to be moved into subprog's r0 set;
- *static* subprog arguments (r1-r5) are moved back to caller precision set.
Let's look at what happens with callee-saved precision propagation. Insn #14
mark r6 as precise. When we get into subprog's frame, we keep r6 in
frame 0's precision set *only*. Subprog itself has its own set of
independent r6-r10 registers and is not affected. When we eventually
made our way out of subprog frame we keep r6 in precision set until we
reach `9: r6 = 456;`, satisfying propagation. r6-r10 propagation is
perhaps the simplest aspect, it always stays in its original frame.
That's pretty much all we have to do to support precision propagation
across *static subprog* invocation.
Let's look at what happens when we have global subprog invocation.
frame 0 frame 1 precision set
======= ======= =============
9: r6 = 456;
10: r1 = 123; fr0: r6
11: call pc+10; # global subprog fr0: r6
12: r1 = <map_pointer> fr0: r0, r6
13: r1 += r0; fr0: r0, r6
14: r1 += r6; fr0: r6;
15: exit
Starting from insn #13, r0 has to be precise. We backtrack all the way
to insn #11 (call pc+10) and see that subprog is global, so was already
validated in isolation. As opposed to static subprog, global subprog
always returns unknown scalar r0, so that satisfies precision
propagation and we drop r0 from precision set. We are done for insns #13.
Now for insn #14. r6 is in precision set, we backtrack to `call pc+10;`.
Here we need to recognize that this is effectively both exit and entry
to global subprog, which means we stay in caller's frame. So we carry on
with r6 still in precision set, until we satisfy it at insn #9. The only
hard part with global subprogs is just knowing when it's a global func.
Lastly, callback-calling helpers and kfuncs do simulate subprog calls,
so jump history will have subprog instructions in between caller
program's instructions, but the rules of propagating r0 and r1-r5
differ, because we don't actually directly call callback. We actually
call helper/kfunc, which at runtime will call subprog, so the only
difference between normal helper/kfunc handling is that we need to make
sure to skip callback simulatinog part of jump history.
Let's look at an example to make this clearer.
frame 0 frame 1 precision set
======= ======= =============
8: r6 = 456;
9: r1 = 123; fr0: r6
10: r2 = &callback; fr0: r6
11: call bpf_loop; fr0: r6
22: r0 = r1; fr0: r6 fr1:
23: exit fr0: r6 fr1:
12: r1 = <map_pointer> fr0: r0, r6
13: r1 += r0; fr0: r0, r6
14: r1 += r6; fr0: r6;
15: exit
Again, insn #13 forces r0 to be precise. As soon as we get to `23: exit`
we see that this isn't actually a static subprog call (it's `call
bpf_loop;` helper call instead). So we clear r0 from precision set.
For callee-saved register, there is no difference: it stays in frame 0's
precision set, we go through insn #22 and #23, ignoring them until we
get back to caller frame 0, eventually satisfying precision backtrack
logic at insn #8 (`r6 = 456;`).
Assuming callback needed to set r0 as precise at insn #23, we'd
backtrack to insn #22, switching from r0 to r1, and then at the point
when we pop back to frame 0 at insn #11, we'll clear r1-r5 from
precision set, as we don't really do a subprog call directly, so there
is no input argument precision propagation.
That's pretty much it. With these changes, it seems like the only still
unsupported situation for precision backpropagation is the case when
program is accessing stack through registers other than r10. This is
still left as unsupported (though rare) case for now.
As for results. For selftests, few positive changes for bigger programs,
cls_redirect in dynptr variant benefitting the most:
[vmuser@archvm bpf]$ ./veristat -C ~/subprog-precise-before-results.csv ~/subprog-precise-after-results.csv -f @veristat.cfg -e file,prog,insns -f 'insns_diff!=0'
File Program Insns (A) Insns (B) Insns (DIFF)
---------------------------------------- ------------- --------- --------- ----------------
pyperf600_bpf_loop.bpf.linked1.o on_event 2060 2002 -58 (-2.82%)
test_cls_redirect_dynptr.bpf.linked1.o cls_redirect 15660 2914 -12746 (-81.39%)
test_cls_redirect_subprogs.bpf.linked1.o cls_redirect 61620 59088 -2532 (-4.11%)
xdp_synproxy_kern.bpf.linked1.o syncookie_tc 109980 86278 -23702 (-21.55%)
xdp_synproxy_kern.bpf.linked1.o syncookie_xdp 97716 85147 -12569 (-12.86%)
Cilium progress don't really regress. They don't use subprogs and are
mostly unaffected, but some other fixes and improvements could have
changed something. This doesn't appear to be the case:
[vmuser@archvm bpf]$ ./veristat -C ~/subprog-precise-before-results-cilium.csv ~/subprog-precise-after-results-cilium.csv -e file,prog,insns -f 'insns_diff!=0'
File Program Insns (A) Insns (B) Insns (DIFF)
------------- ------------------------------ --------- --------- ------------
bpf_host.o tail_nodeport_nat_ingress_ipv6 4983 5003 +20 (+0.40%)
bpf_lxc.o tail_nodeport_nat_ingress_ipv6 4983 5003 +20 (+0.40%)
bpf_overlay.o tail_nodeport_nat_ingress_ipv6 4983 5003 +20 (+0.40%)
bpf_xdp.o tail_handle_nat_fwd_ipv6 12475 12504 +29 (+0.23%)
bpf_xdp.o tail_nodeport_nat_ingress_ipv6 6363 6371 +8 (+0.13%)
Looking at (somewhat anonymized) Meta production programs, we see mostly
insignificant variation in number of instructions, with one program
(syar_bind6_protect6) benefitting the most at -17%.
[vmuser@archvm bpf]$ ./veristat -C ~/subprog-precise-before-results-fbcode.csv ~/subprog-precise-after-results-fbcode.csv -e prog,insns -f 'insns_diff!=0'
Program Insns (A) Insns (B) Insns (DIFF)
------------------------ --------- --------- ----------------
on_request_context_event 597 585 -12 (-2.01%)
read_async_py_stack 43789 43657 -132 (-0.30%)
read_sync_py_stack 35041 37599 +2558 (+7.30%)
rrm_usdt 946 940 -6 (-0.63%)
sysarmor_inet6_bind 28863 28249 -614 (-2.13%)
sysarmor_inet_bind 28845 28240 -605 (-2.10%)
syar_bind4_protect4 154145 147640 -6505 (-4.22%)
syar_bind6_protect6 165242 137088 -28154 (-17.04%)
syar_task_exit_setgid 21289 19720 -1569 (-7.37%)
syar_task_exit_setuid 21290 19721 -1569 (-7.37%)
do_uprobe 19967 19413 -554 (-2.77%)
tw_twfw_ingress 215877 204833 -11044 (-5.12%)
tw_twfw_tc_in 215877 204833 -11044 (-5.12%)
But checking duration (wall clock) differences, that is the actual time taken
by verifier to validate programs, we see a sometimes dramatic improvements, all
the way to about 16x improvements:
[vmuser@archvm bpf]$ ./veristat -C ~/subprog-precise-before-results-meta.csv ~/subprog-precise-after-results-meta.csv -e prog,duration -s duration_diff^ | head -n20
Program Duration (us) (A) Duration (us) (B) Duration (us) (DIFF)
---------------------------------------- ----------------- ----------------- --------------------
tw_twfw_ingress 4488374 272836 -4215538 (-93.92%)
tw_twfw_tc_in 4339111 268175 -4070936 (-93.82%)
tw_twfw_egress 3521816 270751 -3251065 (-92.31%)
tw_twfw_tc_eg 3472878 284294 -3188584 (-91.81%)
balancer_ingress 343119 291391 -51728 (-15.08%)
syar_bind6_protect6 78992 64782 -14210 (-17.99%)
ttls_tc_ingress 11739 8176 -3563 (-30.35%)
kprobe__security_inode_link 13864 11341 -2523 (-18.20%)
read_sync_py_stack 21927 19442 -2485 (-11.33%)
read_async_py_stack 30444 28136 -2308 (-7.58%)
syar_task_exit_setuid 10256 8440 -1816 (-17.71%)
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230505043317.3629845-9-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Andrii Nakryiko
|
c50c0b57a5 |
bpf: fix mark_all_scalars_precise use in mark_chain_precision
When precision backtracking bails out due to some unsupported sequence of instructions (e.g., stack access through register other than r10), we need to mark all SCALAR registers as precise to be safe. Currently, though, we mark SCALARs precise only starting from the state we detected unsupported condition, which could be one of the parent states of the actual current state. This will leave some registers potentially not marked as precise, even though they should. So make sure we start marking scalars as precise from current state (env->cur_state). Further, we don't currently detect a situation when we end up with some stack slots marked as needing precision, but we ran out of available states to find the instructions that populate those stack slots. This is akin the `i >= func->allocated_stack / BPF_REG_SIZE` check and should be handled similarly by falling back to marking all SCALARs precise. Add this check when we run out of states. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230505043317.3629845-8-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Andrii Nakryiko
|
f655badf2a |
bpf: fix propagate_precision() logic for inner frames
Fix propagate_precision() logic to perform propagation of all necessary
registers and stack slots across all active frames *in one batch step*.
Doing this for each register/slot in each individual frame is wasteful,
but the main problem is that backtracking of instruction in any frame
except the deepest one just doesn't work. This is due to backtracking
logic relying on jump history, and available jump history always starts
(or ends, depending how you view it) in current frame. So, if
prog A (frame #0) called subprog B (frame #1) and we need to propagate
precision of, say, register R6 (callee-saved) within frame #0, we
actually don't even know where jump history that corresponds to prog
A even starts. We'd need to skip subprog part of jump history first to
be able to do this.
Luckily, with struct backtrack_state and __mark_chain_precision()
handling bitmasks tracking/propagation across all active frames at the
same time (added in previous patch), propagate_precision() can be both
fixed and sped up by setting all the necessary bits across all frames
and then performing one __mark_chain_precision() pass. This makes it
unnecessary to skip subprog parts of jump history.
We also improve logging along the way, to clearly specify which
registers' and slots' precision markings are propagated within which
frame. Each frame will have dedicated line and all registers and stack
slots from that frame will be reported in format similar to precision
backtrack regs/stack logging. E.g.:
frame 1: propagating r1,r2,r3,fp-8,fp-16
frame 0: propagating r3,r9,fp-120
Fixes:
|
||
|
Andrii Nakryiko
|
1ef22b6865 |
bpf: maintain bitmasks across all active frames in __mark_chain_precision
Teach __mark_chain_precision logic to maintain register/stack masks across all active frames when going from child state to parent state. Currently this should be mostly no-op, as precision backtracking usually bails out when encountering subprog entry/exit. It's not very apparent from the diff due to increased indentation, but the logic remains the same, except everything is done on specific `fr` frame index. Calls to bt_clear_reg() and bt_clear_slot() are replaced with frame-specific bt_clear_frame_reg() and bt_clear_frame_slot(), where frame index is passed explicitly, instead of using current frame number. We also adjust logging to emit affected frame number. And we also add better logging of human-readable register and stack slot masks, similar to previous patch. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230505043317.3629845-6-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Andrii Nakryiko
|
d9439c21a9 |
bpf: improve precision backtrack logging
Add helper to format register and stack masks in more human-readable format. Adjust logging a bit during backtrack propagation and especially during forcing precision fallback logic to make it clearer what's going on (with log_level=2, of course), and also start reporting affected frame depth. This is in preparation for having more than one active frame later when precision propagation between subprog calls is added. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230505043317.3629845-5-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Andrii Nakryiko
|
407958a0e9 |
bpf: encapsulate precision backtracking bookkeeping
Add struct backtrack_state and straightforward API around it to keep track of register and stack masks used and maintained during precision backtracking process. Having this logic separately allow to keep high-level backtracking algorithm cleaner, but also it sets us up to cleanly keep track of register and stack masks per frame, allowing (with some further logic adjustments) to perform precision backpropagation across multiple frames (i.e., subprog calls). Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230505043317.3629845-4-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Andrii Nakryiko
|
e0bf462276 |
bpf: mark relevant stack slots scratched for register read instructions
When handling instructions that read register slots, mark relevant stack slots as scratched so that verifier log would contain those slots' states, in addition to currently emitted registers with stack slot offsets. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230505043317.3629845-3-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
Joanne Koong
|
361f129f3c |
bpf: Add bpf_dynptr_clone
The cloned dynptr will point to the same data as its parent dynptr, with the same type, offset, size and read-only properties. Any writes to a dynptr will be reflected across all instances (by 'instance', this means any dynptrs that point to the same underlying data). Please note that data slice and dynptr invalidations will affect all instances as well. For example, if bpf_dynptr_write() is called on an skb-type dynptr, all data slices of dynptr instances to that skb will be invalidated as well (eg data slices of any clones, parents, grandparents, ...). Another example is if a ringbuf dynptr is submitted, any instance of that dynptr will be invalidated. Changing the view of the dynptr (eg advancing the offset or trimming the size) will only affect that dynptr and not affect any other instances. One example use case where cloning may be helpful is for hashing or iterating through dynptr data. Cloning will allow the user to maintain the original view of the dynptr for future use, while also allowing views to smaller subsets of the data after the offset is advanced or the size is trimmed. Signed-off-by: Joanne Koong <joannelkoong@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20230420071414.570108-5-joannelkoong@gmail.com |
||
|
Yafang Shao
|
a0c109dcaf |
bpf: Add __rcu_read_{lock,unlock} into btf id deny list
The tracing recursion prevention mechanism must be protected by rcu, that
leaves __rcu_read_{lock,unlock} unprotected by this mechanism. If we trace
them, the recursion will happen. Let's add them into the btf id deny list.
When CONFIG_PREEMPT_RCU is enabled, it can be reproduced with a simple bpf
program as such:
SEC("fentry/__rcu_read_lock")
int fentry_run()
{
return 0;
}
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20230424161104.3737-2-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Dave Marchevsky
|
7deca5eae8 |
bpf: Disable bpf_refcount_acquire kfunc calls until race conditions are fixed
As reported by Kumar in [0], the shared ownership implementation for BPF programs has some race conditions which need to be addressed before it can safely be used. This patch does so in a minimal way instead of ripping out shared ownership entirely, as proper fixes for the issues raised will follow ASAP, at which point this patch's commit can be reverted to re-enable shared ownership. The patch removes the ability to call bpf_refcount_acquire_impl from BPF programs. Programs can only bump refcount and obtain a new owning reference using this kfunc, so removing the ability to call it effectively disables shared ownership. Instead of changing success / failure expectations for bpf_refcount-related selftests, this patch just disables them from running for now. [0]: https://lore.kernel.org/bpf/d7hyspcow5wtjcmw4fugdgyp3fwhljwuscp3xyut5qnwivyeru@ysdq543otzv2/ Reported-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> Link: https://lore.kernel.org/r/20230424204321.2680232-1-davemarchevsky@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Jakub Kicinski
|
9a82cdc28f |
bpf-next-for-netdev
-----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQTFp0I1jqZrAX+hPRXbK58LschIgwUCZELn8wAKCRDbK58LschI g1khAQC1nmXPuKjM4EAfFK8Ysb3KoF8ADmpE97n+/HEDydCagwD/bX0+NABR75Nh ueGcoU1TcfcbshDzrH0s+C95owZDZw4= =BeZM -----END PGP SIGNATURE----- Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next Daniel Borkmann says: ==================== pull-request: bpf-next 2023-04-21 We've added 71 non-merge commits during the last 8 day(s) which contain a total of 116 files changed, 13397 insertions(+), 8896 deletions(-). The main changes are: 1) Add a new BPF netfilter program type and minimal support to hook BPF programs to netfilter hooks such as prerouting or forward, from Florian Westphal. 2) Fix race between btf_put and btf_idr walk which caused a deadlock, from Alexei Starovoitov. 3) Second big batch to migrate test_verifier unit tests into test_progs for ease of readability and debugging, from Eduard Zingerman. 4) Add support for refcounted local kptrs to the verifier for allowing shared ownership, useful for adding a node to both the BPF list and rbtree, from Dave Marchevsky. 5) Migrate bpf_for(), bpf_for_each() and bpf_repeat() macros from BPF selftests into libbpf-provided bpf_helpers.h header and improve kfunc handling, from Andrii Nakryiko. 6) Support 64-bit pointers to kfuncs needed for archs like s390x, from Ilya Leoshkevich. 7) Support BPF progs under getsockopt with a NULL optval, from Stanislav Fomichev. 8) Improve verifier u32 scalar equality checking in order to enable LLVM transformations which earlier had to be disabled specifically for BPF backend, from Yonghong Song. 9) Extend bpftool's struct_ops object loading to support links, from Kui-Feng Lee. 10) Add xsk selftest follow-up fixes for hugepage allocated umem, from Magnus Karlsson. 11) Support BPF redirects from tc BPF to ifb devices, from Daniel Borkmann. 12) Add BPF support for integer type when accessing variable length arrays, from Feng Zhou. * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (71 commits) selftests/bpf: verifier/value_ptr_arith converted to inline assembly selftests/bpf: verifier/value_illegal_alu converted to inline assembly selftests/bpf: verifier/unpriv converted to inline assembly selftests/bpf: verifier/subreg converted to inline assembly selftests/bpf: verifier/spin_lock converted to inline assembly selftests/bpf: verifier/sock converted to inline assembly selftests/bpf: verifier/search_pruning converted to inline assembly selftests/bpf: verifier/runtime_jit converted to inline assembly selftests/bpf: verifier/regalloc converted to inline assembly selftests/bpf: verifier/ref_tracking converted to inline assembly selftests/bpf: verifier/map_ptr_mixing converted to inline assembly selftests/bpf: verifier/map_in_map converted to inline assembly selftests/bpf: verifier/lwt converted to inline assembly selftests/bpf: verifier/loops1 converted to inline assembly selftests/bpf: verifier/jeq_infer_not_null converted to inline assembly selftests/bpf: verifier/direct_packet_access converted to inline assembly selftests/bpf: verifier/d_path converted to inline assembly selftests/bpf: verifier/ctx converted to inline assembly selftests/bpf: verifier/btf_ctx_access converted to inline assembly selftests/bpf: verifier/bpf_get_stack converted to inline assembly ... ==================== Link: https://lore.kernel.org/r/20230421211035.9111-1-daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org> |
||
Florian Westphal
|
fd9c663b9a |
bpf: minimal support for programs hooked into netfilter framework
This adds minimal support for BPF_PROG_TYPE_NETFILTER bpf programs that will be invoked via the NF_HOOK() points in the ip stack. Invocation incurs an indirect call. This is not a necessity: Its possible to add 'DEFINE_BPF_DISPATCHER(nf_progs)' and handle the program invocation with the same method already done for xdp progs. This isn't done here to keep the size of this chunk down. Verifier restricts verdicts to either DROP or ACCEPT. Signed-off-by: Florian Westphal <fw@strlen.de> Link: https://lore.kernel.org/r/20230421170300.24115-3-fw@strlen.de Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Jakub Kicinski
|
681c5b51dc |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Adjacent changes: net/mptcp/protocol.h |
||
Daniel Borkmann
|
71b547f561 |
bpf: Fix incorrect verifier pruning due to missing register precision taints
Juan Jose et al reported an issue found via fuzzing where the verifier's
pruning logic prematurely marks a program path as safe.
Consider the following program:
0: (b7) r6 = 1024
1: (b7) r7 = 0
2: (b7) r8 = 0
3: (b7) r9 = -2147483648
4: (97) r6 %= 1025
5: (05) goto pc+0
6: (bd) if r6 <= r9 goto pc+2
7: (97) r6 %= 1
8: (b7) r9 = 0
9: (bd) if r6 <= r9 goto pc+1
10: (b7) r6 = 0
11: (b7) r0 = 0
12: (63) *(u32 *)(r10 -4) = r0
13: (18) r4 = 0xffff888103693400 // map_ptr(ks=4,vs=48)
15: (bf) r1 = r4
16: (bf) r2 = r10
17: (07) r2 += -4
18: (85) call bpf_map_lookup_elem#1
19: (55) if r0 != 0x0 goto pc+1
20: (95) exit
21: (77) r6 >>= 10
22: (27) r6 *= 8192
23: (bf) r1 = r0
24: (0f) r0 += r6
25: (79) r3 = *(u64 *)(r0 +0)
26: (7b) *(u64 *)(r1 +0) = r3
27: (95) exit
The verifier treats this as safe, leading to oob read/write access due
to an incorrect verifier conclusion:
func#0 @0
0: R1=ctx(off=0,imm=0) R10=fp0
0: (b7) r6 = 1024 ; R6_w=1024
1: (b7) r7 = 0 ; R7_w=0
2: (b7) r8 = 0 ; R8_w=0
3: (b7) r9 = -2147483648 ; R9_w=-2147483648
4: (97) r6 %= 1025 ; R6_w=scalar()
5: (05) goto pc+0
6: (bd) if r6 <= r9 goto pc+2 ; R6_w=scalar(umin=18446744071562067969,var_off=(0xffffffff00000000; 0xffffffff)) R9_w=-2147483648
7: (97) r6 %= 1 ; R6_w=scalar()
8: (b7) r9 = 0 ; R9=0
9: (bd) if r6 <= r9 goto pc+1 ; R6=scalar(umin=1) R9=0
10: (b7) r6 = 0 ; R6_w=0
11: (b7) r0 = 0 ; R0_w=0
12: (63) *(u32 *)(r10 -4) = r0
last_idx 12 first_idx 9
regs=1 stack=0 before 11: (b7) r0 = 0
13: R0_w=0 R10=fp0 fp-8=0000????
13: (18) r4 = 0xffff8ad3886c2a00 ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
15: (bf) r1 = r4 ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
16: (bf) r2 = r10 ; R2_w=fp0 R10=fp0
17: (07) r2 += -4 ; R2_w=fp-4
18: (85) call bpf_map_lookup_elem#1 ; R0=map_value_or_null(id=1,off=0,ks=4,vs=48,imm=0)
19: (55) if r0 != 0x0 goto pc+1 ; R0=0
20: (95) exit
from 19 to 21: R0=map_value(off=0,ks=4,vs=48,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0 fp-8=mmmm????
21: (77) r6 >>= 10 ; R6_w=0
22: (27) r6 *= 8192 ; R6_w=0
23: (bf) r1 = r0 ; R0=map_value(off=0,ks=4,vs=48,imm=0) R1_w=map_value(off=0,ks=4,vs=48,imm=0)
24: (0f) r0 += r6
last_idx 24 first_idx 19
regs=40 stack=0 before 23: (bf) r1 = r0
regs=40 stack=0 before 22: (27) r6 *= 8192
regs=40 stack=0 before 21: (77) r6 >>= 10
regs=40 stack=0 before 19: (55) if r0 != 0x0 goto pc+1
parent didn't have regs=40 stack=0 marks: R0_rw=map_value_or_null(id=1,off=0,ks=4,vs=48,imm=0) R6_rw=P0 R7=0 R8=0 R9=0 R10=fp0 fp-8=mmmm????
last_idx 18 first_idx 9
regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
regs=40 stack=0 before 17: (07) r2 += -4
regs=40 stack=0 before 16: (bf) r2 = r10
regs=40 stack=0 before 15: (bf) r1 = r4
regs=40 stack=0 before 13: (18) r4 = 0xffff8ad3886c2a00
regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
regs=40 stack=0 before 11: (b7) r0 = 0
regs=40 stack=0 before 10: (b7) r6 = 0
25: (79) r3 = *(u64 *)(r0 +0) ; R0_w=map_value(off=0,ks=4,vs=48,imm=0) R3_w=scalar()
26: (7b) *(u64 *)(r1 +0) = r3 ; R1_w=map_value(off=0,ks=4,vs=48,imm=0) R3_w=scalar()
27: (95) exit
from 9 to 11: R1=ctx(off=0,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0
11: (b7) r0 = 0 ; R0_w=0
12: (63) *(u32 *)(r10 -4) = r0
last_idx 12 first_idx 11
regs=1 stack=0 before 11: (b7) r0 = 0
13: R0_w=0 R10=fp0 fp-8=0000????
13: (18) r4 = 0xffff8ad3886c2a00 ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
15: (bf) r1 = r4 ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
16: (bf) r2 = r10 ; R2_w=fp0 R10=fp0
17: (07) r2 += -4 ; R2_w=fp-4
18: (85) call bpf_map_lookup_elem#1
frame 0: propagating r6
last_idx 19 first_idx 11
regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
regs=40 stack=0 before 17: (07) r2 += -4
regs=40 stack=0 before 16: (bf) r2 = r10
regs=40 stack=0 before 15: (bf) r1 = r4
regs=40 stack=0 before 13: (18) r4 = 0xffff8ad3886c2a00
regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
regs=40 stack=0 before 11: (b7) r0 = 0
parent didn't have regs=40 stack=0 marks: R1=ctx(off=0,imm=0) R6_r=P0 R7=0 R8=0 R9=0 R10=fp0
last_idx 9 first_idx 9
regs=40 stack=0 before 9: (bd) if r6 <= r9 goto pc+1
parent didn't have regs=40 stack=0 marks: R1=ctx(off=0,imm=0) R6_rw=Pscalar() R7_w=0 R8_w=0 R9_rw=0 R10=fp0
last_idx 8 first_idx 0
regs=40 stack=0 before 8: (b7) r9 = 0
regs=40 stack=0 before 7: (97) r6 %= 1
regs=40 stack=0 before 6: (bd) if r6 <= r9 goto pc+2
regs=40 stack=0 before 5: (05) goto pc+0
regs=40 stack=0 before 4: (97) r6 %= 1025
regs=40 stack=0 before 3: (b7) r9 = -2147483648
regs=40 stack=0 before 2: (b7) r8 = 0
regs=40 stack=0 before 1: (b7) r7 = 0
regs=40 stack=0 before 0: (b7) r6 = 1024
19: safe
frame 0: propagating r6
last_idx 9 first_idx 0
regs=40 stack=0 before 6: (bd) if r6 <= r9 goto pc+2
regs=40 stack=0 before 5: (05) goto pc+0
regs=40 stack=0 before 4: (97) r6 %= 1025
regs=40 stack=0 before 3: (b7) r9 = -2147483648
regs=40 stack=0 before 2: (b7) r8 = 0
regs=40 stack=0 before 1: (b7) r7 = 0
regs=40 stack=0 before 0: (b7) r6 = 1024
from 6 to 9: safe
verification time 110 usec
stack depth 4
processed 36 insns (limit 1000000) max_states_per_insn 0 total_states 3 peak_states 3 mark_read 2
The verifier considers this program as safe by mistakenly pruning unsafe
code paths. In the above func#0, code lines 0-10 are of interest. In line
0-3 registers r6 to r9 are initialized with known scalar values. In line 4
the register r6 is reset to an unknown scalar given the verifier does not
track modulo operations. Due to this, the verifier can also not determine
precisely which branches in line 6 and 9 are taken, therefore it needs to
explore them both.
As can be seen, the verifier starts with exploring the false/fall-through
paths first. The 'from 19 to 21' path has both r6=0 and r9=0 and the pointer
arithmetic on r0 += r6 is therefore considered safe. Given the arithmetic,
r6 is correctly marked for precision tracking where backtracking kicks in
where it walks back the current path all the way where r6 was set to 0 in
the fall-through branch.
Next, the pruning logics pops the path 'from 9 to 11' from the stack. Also
here, the state of the registers is the same, that is, r6=0 and r9=0, so
that at line 19 the path can be pruned as it is considered safe. It is
interesting to note that the conditional in line 9 turned r6 into a more
precise state, that is, in the fall-through path at the beginning of line
10, it is R6=scalar(umin=1), and in the branch-taken path (which is analyzed
here) at the beginning of line 11, r6 turned into a known const r6=0 as
r9=0 prior to that and therefore (unsigned) r6 <= 0 concludes that r6 must
be 0 (**):
[...] ; R6_w=scalar()
9: (bd) if r6 <= r9 goto pc+1 ; R6=scalar(umin=1) R9=0
[...]
from 9 to 11: R1=ctx(off=0,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0
[...]
The next path is 'from 6 to 9'. The verifier considers the old and current
state equivalent, and therefore prunes the search incorrectly. Looking into
the two states which are being compared by the pruning logic at line 9, the
old state consists of R6_rwD=Pscalar() R9_rwD=0 R10=fp0 and the new state
consists of R1=ctx(off=0,imm=0) R6_w=scalar(umax=18446744071562067968)
R7_w=0 R8_w=0 R9_w=-2147483648 R10=fp0. While r6 had the reg->precise flag
correctly set in the old state, r9 did not. Both r6'es are considered as
equivalent given the old one is a superset of the current, more precise one,
however, r9's actual values (0 vs 0x80000000) mismatch. Given the old r9
did not have reg->precise flag set, the verifier does not consider the
register as contributing to the precision state of r6, and therefore it
considered both r9 states as equivalent. However, for this specific pruned
path (which is also the actual path taken at runtime), register r6 will be
0x400 and r9 0x80000000 when reaching line 21, thus oob-accessing the map.
The purpose of precision tracking is to initially mark registers (including
spilled ones) as imprecise to help verifier's pruning logic finding equivalent
states it can then prune if they don't contribute to the program's safety
aspects. For example, if registers are used for pointer arithmetic or to pass
constant length to a helper, then the verifier sets reg->precise flag and
backtracks the BPF program instruction sequence and chain of verifier states
to ensure that the given register or stack slot including their dependencies
are marked as precisely tracked scalar. This also includes any other registers
and slots that contribute to a tracked state of given registers/stack slot.
This backtracking relies on recorded jmp_history and is able to traverse
entire chain of parent states. This process ends only when all the necessary
registers/slots and their transitive dependencies are marked as precise.
The backtrack_insn() is called from the current instruction up to the first
instruction, and its purpose is to compute a bitmask of registers and stack
slots that need precision tracking in the parent's verifier state. For example,
if a current instruction is r6 = r7, then r6 needs precision after this
instruction and r7 needs precision before this instruction, that is, in the
parent state. Hence for the latter r7 is marked and r6 unmarked.
For the class of jmp/jmp32 instructions, backtrack_insn() today only looks
at call and exit instructions and for all other conditionals the masks
remain as-is. However, in the given situation register r6 has a dependency
on r9 (as described above in **), so also that one needs to be marked for
precision tracking. In other words, if an imprecise register influences a
precise one, then the imprecise register should also be marked precise.
Meaning, in the parent state both dest and src register need to be tracked
for precision and therefore the marking must be more conservative by setting
reg->precise flag for both. The precision propagation needs to cover both
for the conditional: if the src reg was marked but not the dst reg and vice
versa.
After the fix the program is correctly rejected:
func#0 @0
0: R1=ctx(off=0,imm=0) R10=fp0
0: (b7) r6 = 1024 ; R6_w=1024
1: (b7) r7 = 0 ; R7_w=0
2: (b7) r8 = 0 ; R8_w=0
3: (b7) r9 = -2147483648 ; R9_w=-2147483648
4: (97) r6 %= 1025 ; R6_w=scalar()
5: (05) goto pc+0
6: (bd) if r6 <= r9 goto pc+2 ; R6_w=scalar(umin=18446744071562067969,var_off=(0xffffffff80000000; 0x7fffffff),u32_min=-2147483648) R9_w=-2147483648
7: (97) r6 %= 1 ; R6_w=scalar()
8: (b7) r9 = 0 ; R9=0
9: (bd) if r6 <= r9 goto pc+1 ; R6=scalar(umin=1) R9=0
10: (b7) r6 = 0 ; R6_w=0
11: (b7) r0 = 0 ; R0_w=0
12: (63) *(u32 *)(r10 -4) = r0
last_idx 12 first_idx 9
regs=1 stack=0 before 11: (b7) r0 = 0
13: R0_w=0 R10=fp0 fp-8=0000????
13: (18) r4 = 0xffff9290dc5bfe00 ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
15: (bf) r1 = r4 ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
16: (bf) r2 = r10 ; R2_w=fp0 R10=fp0
17: (07) r2 += -4 ; R2_w=fp-4
18: (85) call bpf_map_lookup_elem#1 ; R0=map_value_or_null(id=1,off=0,ks=4,vs=48,imm=0)
19: (55) if r0 != 0x0 goto pc+1 ; R0=0
20: (95) exit
from 19 to 21: R0=map_value(off=0,ks=4,vs=48,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0 fp-8=mmmm????
21: (77) r6 >>= 10 ; R6_w=0
22: (27) r6 *= 8192 ; R6_w=0
23: (bf) r1 = r0 ; R0=map_value(off=0,ks=4,vs=48,imm=0) R1_w=map_value(off=0,ks=4,vs=48,imm=0)
24: (0f) r0 += r6
last_idx 24 first_idx 19
regs=40 stack=0 before 23: (bf) r1 = r0
regs=40 stack=0 before 22: (27) r6 *= 8192
regs=40 stack=0 before 21: (77) r6 >>= 10
regs=40 stack=0 before 19: (55) if r0 != 0x0 goto pc+1
parent didn't have regs=40 stack=0 marks: R0_rw=map_value_or_null(id=1,off=0,ks=4,vs=48,imm=0) R6_rw=P0 R7=0 R8=0 R9=0 R10=fp0 fp-8=mmmm????
last_idx 18 first_idx 9
regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
regs=40 stack=0 before 17: (07) r2 += -4
regs=40 stack=0 before 16: (bf) r2 = r10
regs=40 stack=0 before 15: (bf) r1 = r4
regs=40 stack=0 before 13: (18) r4 = 0xffff9290dc5bfe00
regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
regs=40 stack=0 before 11: (b7) r0 = 0
regs=40 stack=0 before 10: (b7) r6 = 0
25: (79) r3 = *(u64 *)(r0 +0) ; R0_w=map_value(off=0,ks=4,vs=48,imm=0) R3_w=scalar()
26: (7b) *(u64 *)(r1 +0) = r3 ; R1_w=map_value(off=0,ks=4,vs=48,imm=0) R3_w=scalar()
27: (95) exit
from 9 to 11: R1=ctx(off=0,imm=0) R6=0 R7=0 R8=0 R9=0 R10=fp0
11: (b7) r0 = 0 ; R0_w=0
12: (63) *(u32 *)(r10 -4) = r0
last_idx 12 first_idx 11
regs=1 stack=0 before 11: (b7) r0 = 0
13: R0_w=0 R10=fp0 fp-8=0000????
13: (18) r4 = 0xffff9290dc5bfe00 ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
15: (bf) r1 = r4 ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
16: (bf) r2 = r10 ; R2_w=fp0 R10=fp0
17: (07) r2 += -4 ; R2_w=fp-4
18: (85) call bpf_map_lookup_elem#1
frame 0: propagating r6
last_idx 19 first_idx 11
regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
regs=40 stack=0 before 17: (07) r2 += -4
regs=40 stack=0 before 16: (bf) r2 = r10
regs=40 stack=0 before 15: (bf) r1 = r4
regs=40 stack=0 before 13: (18) r4 = 0xffff9290dc5bfe00
regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
regs=40 stack=0 before 11: (b7) r0 = 0
parent didn't have regs=40 stack=0 marks: R1=ctx(off=0,imm=0) R6_r=P0 R7=0 R8=0 R9=0 R10=fp0
last_idx 9 first_idx 9
regs=40 stack=0 before 9: (bd) if r6 <= r9 goto pc+1
parent didn't have regs=240 stack=0 marks: R1=ctx(off=0,imm=0) R6_rw=Pscalar() R7_w=0 R8_w=0 R9_rw=P0 R10=fp0
last_idx 8 first_idx 0
regs=240 stack=0 before 8: (b7) r9 = 0
regs=40 stack=0 before 7: (97) r6 %= 1
regs=40 stack=0 before 6: (bd) if r6 <= r9 goto pc+2
regs=240 stack=0 before 5: (05) goto pc+0
regs=240 stack=0 before 4: (97) r6 %= 1025
regs=240 stack=0 before 3: (b7) r9 = -2147483648
regs=40 stack=0 before 2: (b7) r8 = 0
regs=40 stack=0 before 1: (b7) r7 = 0
regs=40 stack=0 before 0: (b7) r6 = 1024
19: safe
from 6 to 9: R1=ctx(off=0,imm=0) R6_w=scalar(umax=18446744071562067968) R7_w=0 R8_w=0 R9_w=-2147483648 R10=fp0
9: (bd) if r6 <= r9 goto pc+1
last_idx 9 first_idx 0
regs=40 stack=0 before 6: (bd) if r6 <= r9 goto pc+2
regs=240 stack=0 before 5: (05) goto pc+0
regs=240 stack=0 before 4: (97) r6 %= 1025
regs=240 stack=0 before 3: (b7) r9 = -2147483648
regs=40 stack=0 before 2: (b7) r8 = 0
regs=40 stack=0 before 1: (b7) r7 = 0
regs=40 stack=0 before 0: (b7) r6 = 1024
last_idx 9 first_idx 0
regs=200 stack=0 before 6: (bd) if r6 <= r9 goto pc+2
regs=240 stack=0 before 5: (05) goto pc+0
regs=240 stack=0 before 4: (97) r6 %= 1025
regs=240 stack=0 before 3: (b7) r9 = -2147483648
regs=40 stack=0 before 2: (b7) r8 = 0
regs=40 stack=0 before 1: (b7) r7 = 0
regs=40 stack=0 before 0: (b7) r6 = 1024
11: R6=scalar(umax=18446744071562067968) R9=-2147483648
11: (b7) r0 = 0 ; R0_w=0
12: (63) *(u32 *)(r10 -4) = r0
last_idx 12 first_idx 11
regs=1 stack=0 before 11: (b7) r0 = 0
13: R0_w=0 R10=fp0 fp-8=0000????
13: (18) r4 = 0xffff9290dc5bfe00 ; R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
15: (bf) r1 = r4 ; R1_w=map_ptr(off=0,ks=4,vs=48,imm=0) R4_w=map_ptr(off=0,ks=4,vs=48,imm=0)
16: (bf) r2 = r10 ; R2_w=fp0 R10=fp0
17: (07) r2 += -4 ; R2_w=fp-4
18: (85) call bpf_map_lookup_elem#1 ; R0_w=map_value_or_null(id=3,off=0,ks=4,vs=48,imm=0)
19: (55) if r0 != 0x0 goto pc+1 ; R0_w=0
20: (95) exit
from 19 to 21: R0=map_value(off=0,ks=4,vs=48,imm=0) R6=scalar(umax=18446744071562067968) R7=0 R8=0 R9=-2147483648 R10=fp0 fp-8=mmmm????
21: (77) r6 >>= 10 ; R6_w=scalar(umax=18014398507384832,var_off=(0x0; 0x3fffffffffffff))
22: (27) r6 *= 8192 ; R6_w=scalar(smax=9223372036854767616,umax=18446744073709543424,var_off=(0x0; 0xffffffffffffe000),s32_max=2147475456,u32_max=-8192)
23: (bf) r1 = r0 ; R0=map_value(off=0,ks=4,vs=48,imm=0) R1_w=map_value(off=0,ks=4,vs=48,imm=0)
24: (0f) r0 += r6
last_idx 24 first_idx 21
regs=40 stack=0 before 23: (bf) r1 = r0
regs=40 stack=0 before 22: (27) r6 *= 8192
regs=40 stack=0 before 21: (77) r6 >>= 10
parent didn't have regs=40 stack=0 marks: R0_rw=map_value(off=0,ks=4,vs=48,imm=0) R6_r=Pscalar(umax=18446744071562067968) R7=0 R8=0 R9=-2147483648 R10=fp0 fp-8=mmmm????
last_idx 19 first_idx 11
regs=40 stack=0 before 19: (55) if r0 != 0x0 goto pc+1
regs=40 stack=0 before 18: (85) call bpf_map_lookup_elem#1
regs=40 stack=0 before 17: (07) r2 += -4
regs=40 stack=0 before 16: (bf) r2 = r10
regs=40 stack=0 before 15: (bf) r1 = r4
regs=40 stack=0 before 13: (18) r4 = 0xffff9290dc5bfe00
regs=40 stack=0 before 12: (63) *(u32 *)(r10 -4) = r0
regs=40 stack=0 before 11: (b7) r0 = 0
parent didn't have regs=40 stack=0 marks: R1=ctx(off=0,imm=0) R6_rw=Pscalar(umax=18446744071562067968) R7_w=0 R8_w=0 R9_w=-2147483648 R10=fp0
last_idx 9 first_idx 0
regs=40 stack=0 before 9: (bd) if r6 <= r9 goto pc+1
regs=240 stack=0 before 6: (bd) if r6 <= r9 goto pc+2
regs=240 stack=0 before 5: (05) goto pc+0
regs=240 stack=0 before 4: (97) r6 %= 1025
regs=240 stack=0 before 3: (b7) r9 = -2147483648
regs=40 stack=0 before 2: (b7) r8 = 0
regs=40 stack=0 before 1: (b7) r7 = 0
regs=40 stack=0 before 0: (b7) r6 = 1024
math between map_value pointer and register with unbounded min value is not allowed
verification time 886 usec
stack depth 4
processed 49 insns (limit 1000000) max_states_per_insn 1 total_states 5 peak_states 5 mark_read 2
Fixes:
|
||
Yonghong Song
|
3be49f7955 |
bpf: Improve verifier u32 scalar equality checking
In [1], I tried to remove bpf-specific codes to prevent certain
llvm optimizations, and add llvm TTI (target transform info) hooks
to prevent those optimizations. During this process, I found
if I enable llvm SimplifyCFG:shouldFoldTwoEntryPHINode
transformation, I will hit the following verification failure with selftests:
...
8: (18) r1 = 0xffffc900001b2230 ; R1_w=map_value(off=560,ks=4,vs=564,imm=0)
10: (61) r1 = *(u32 *)(r1 +0) ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
; if (skb->tstamp == EGRESS_ENDHOST_MAGIC)
11: (79) r2 = *(u64 *)(r6 +152) ; R2_w=scalar() R6=ctx(off=0,imm=0)
; if (skb->tstamp == EGRESS_ENDHOST_MAGIC)
12: (55) if r2 != 0xb9fbeef goto pc+10 ; R2_w=195018479
13: (bc) w2 = w1 ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R2_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
; if (test < __NR_TESTS)
14: (a6) if w1 < 0x9 goto pc+1 16: R0=2 R1_w=scalar(umax=8,var_off=(0x0; 0xf)) R2_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R6=ctx(off=0,imm=0) R10=fp0
;
16: (27) r2 *= 28 ; R2_w=scalar(umax=120259084260,var_off=(0x0; 0x1ffffffffc),s32_max=2147483644,u32_max=-4)
17: (18) r3 = 0xffffc900001b2118 ; R3_w=map_value(off=280,ks=4,vs=564,imm=0)
19: (0f) r3 += r2 ; R2_w=scalar(umax=120259084260,var_off=(0x0; 0x1ffffffffc),s32_max=2147483644,u32_max=-4) R3_w=map_value(off=280,ks=4,vs=564,umax=120259084260,var_off=(0x0; 0x1ffffffffc),s32_max=2147483644,u32_max=-4)
20: (61) r2 = *(u32 *)(r3 +0)
R3 unbounded memory access, make sure to bounds check any such access
processed 97 insns (limit 1000000) max_states_per_insn 1 total_states 10 peak_states 10 mark_read 6
-- END PROG LOAD LOG --
libbpf: prog 'ingress_fwdns_prio100': failed to load: -13
libbpf: failed to load object 'test_tc_dtime'
libbpf: failed to load BPF skeleton 'test_tc_dtime': -13
...
At insn 14, with condition 'w1 < 9', register r1 is changed from an arbitrary
u32 value to `scalar(umax=8,var_off=(0x0; 0xf))`. Register r2, however, remains
as an arbitrary u32 value. Current verifier won't claim r1/r2 equality if
the previous mov is alu32 ('w2 = w1').
If r1 upper 32bit value is not 0, we indeed cannot clamin r1/r2 equality
after 'w2 = w1'. But in this particular case, we know r1 upper 32bit value
is 0, so it is safe to claim r1/r2 equality. This patch exactly did this.
For a 32bit subreg mov, if the src register upper 32bit is 0,
it is okay to claim equality between src and dst registers.
With this patch, the above verification sequence becomes
...
8: (18) r1 = 0xffffc9000048e230 ; R1_w=map_value(off=560,ks=4,vs=564,imm=0)
10: (61) r1 = *(u32 *)(r1 +0) ; R1_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff))
; if (skb->tstamp == EGRESS_ENDHOST_MAGIC)
11: (79) r2 = *(u64 *)(r6 +152) ; R2_w=scalar() R6=ctx(off=0,imm=0)
; if (skb->tstamp == EGRESS_ENDHOST_MAGIC)
12: (55) if r2 != 0xb9fbeef goto pc+10 ; R2_w=195018479
13: (bc) w2 = w1 ; R1_w=scalar(id=6,umax=4294967295,var_off=(0x0; 0xffffffff)) R2_w=scalar(id=6,umax=4294967295,var_off=(0x0; 0xffffffff))
; if (test < __NR_TESTS)
14: (a6) if w1 < 0x9 goto pc+1 ; R1_w=scalar(id=6,umin=9,umax=4294967295,var_off=(0x0; 0xffffffff))
...
from 14 to 16: R0=2 R1_w=scalar(id=6,umax=8,var_off=(0x0; 0xf)) R2_w=scalar(id=6,umax=8,var_off=(0x0; 0xf)) R6=ctx(off=0,imm=0) R10=fp0
16: (27) r2 *= 28 ; R2_w=scalar(umax=224,var_off=(0x0; 0xfc))
17: (18) r3 = 0xffffc9000048e118 ; R3_w=map_value(off=280,ks=4,vs=564,imm=0)
19: (0f) r3 += r2
20: (61) r2 = *(u32 *)(r3 +0) ; R2_w=scalar(umax=4294967295,var_off=(0x0; 0xffffffff)) R3_w=map_value(off=280,ks=4,vs=564,umax=224,var_off=(0x0; 0xfc),s32_max=252,u32_max=252)
...
and eventually the bpf program can be verified successfully.
[1] https://reviews.llvm.org/D147968
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20230417222134.359714-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
David Vernet
|
7b4ddf3920 |
bpf: Remove KF_KPTR_GET kfunc flag
We've managed to improve the UX for kptrs significantly over the last 9
months. All of the existing use cases which previously had KF_KPTR_GET
kfuncs (struct bpf_cpumask *, struct task_struct *, and struct cgroup *)
have all been updated to be synchronized using RCU. In other words,
their KF_KPTR_GET kfuncs have been removed in favor of KF_RCU |
KF_ACQUIRE kfuncs, with the pointers themselves also being readable from
maps in an RCU read region thanks to the types being RCU safe.
While KF_KPTR_GET was a logical starting point for kptrs, it's become
clear that they're not the correct abstraction. KF_KPTR_GET is a flag
that essentially does nothing other than enforcing that the argument to
a function is a pointer to a referenced kptr map value. At first glance,
that's a useful thing to guarantee to a kfunc. It gives kfuncs the
ability to try and acquire a reference on that kptr without requiring
the BPF prog to do something like this:
struct kptr_type *in_map, *new = NULL;
in_map = bpf_kptr_xchg(&map->value, NULL);
if (in_map) {
new = bpf_kptr_type_acquire(in_map);
in_map = bpf_kptr_xchg(&map->value, in_map);
if (in_map)
bpf_kptr_type_release(in_map);
}
That's clearly a pretty ugly (and racy) UX, and if using KF_KPTR_GET is
the only alternative, it's better than nothing. However, the problem
with any KF_KPTR_GET kfunc lies in the fact that it always requires some
kind of synchronization in order to safely do an opportunistic acquire
of the kptr in the map. This is because a BPF program running on another
CPU could do a bpf_kptr_xchg() on that map value, and free the kptr
after it's been read by the KF_KPTR_GET kfunc. For example, the
now-removed bpf_task_kptr_get() kfunc did the following:
struct task_struct *bpf_task_kptr_get(struct task_struct **pp)
{
struct task_struct *p;
rcu_read_lock();
p = READ_ONCE(*pp);
/* If p is non-NULL, it could still be freed by another CPU,
* so we have to do an opportunistic refcount_inc_not_zero()
* and return NULL if the task will be freed after the
* current RCU read region.
*/
|f (p && !refcount_inc_not_zero(&p->rcu_users))
p = NULL;
rcu_read_unlock();
return p;
}
In other words, the kfunc uses RCU to ensure that the task remains valid
after it's been peeked from the map. However, this is completely
redundant with just defining a KF_RCU kfunc that itself does a
refcount_inc_not_zero(), which is exactly what bpf_task_acquire() now
does.
So, the question of whether KF_KPTR_GET is useful is actually, "Are
there any synchronization mechanisms / safety flags that are required by
certain kptrs, but which are not provided by the verifier to kfuncs?"
The answer to that question today is "No", because every kptr we
currently care about is RCU protected.
Even if the answer ever became "yes", the proper way to support that
referenced kptr type would be to add support for whatever
synchronization mechanism it requires in the verifier, rather than
giving kfuncs a flag that says, "Here's a pointer to a referenced kptr
in a map, do whatever you need to do."
With all that said -- so as to allow us to consolidate the kfunc API,
and simplify the verifier a bit, this patch removes KF_KPTR_GET, and all
relevant logic from the verifier.
Signed-off-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230416084928.326135-3-void@manifault.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Dave Marchevsky
|
404ad75a36 |
bpf: Migrate bpf_rbtree_remove to possibly fail
This patch modifies bpf_rbtree_remove to account for possible failure
due to the input rb_node already not being in any collection.
The function can now return NULL, and does when the aforementioned
scenario occurs. As before, on successful removal an owning reference to
the removed node is returned.
Adding KF_RET_NULL to bpf_rbtree_remove's kfunc flags - now KF_RET_NULL |
KF_ACQUIRE - provides the desired verifier semantics:
* retval must be checked for NULL before use
* if NULL, retval's ref_obj_id is released
* retval is a "maybe acquired" owning ref, not a non-owning ref,
so it will live past end of critical section (bpf_spin_unlock), and
thus can be checked for NULL after the end of the CS
BPF programs must add checks
============================
This does change bpf_rbtree_remove's verifier behavior. BPF program
writers will need to add NULL checks to their programs, but the
resulting UX looks natural:
bpf_spin_lock(&glock);
n = bpf_rbtree_first(&ghead);
if (!n) { /* ... */}
res = bpf_rbtree_remove(&ghead, &n->node);
bpf_spin_unlock(&glock);
if (!res) /* Newly-added check after this patch */
return 1;
n = container_of(res, /* ... */);
/* Do something else with n */
bpf_obj_drop(n);
return 0;
The "if (!res)" check above is the only addition necessary for the above
program to pass verification after this patch.
bpf_rbtree_remove no longer clobbers non-owning refs
====================================================
An issue arises when bpf_rbtree_remove fails, though. Consider this
example:
struct node_data {
long key;
struct bpf_list_node l;
struct bpf_rb_node r;
struct bpf_refcount ref;
};
long failed_sum;
void bpf_prog()
{
struct node_data *n = bpf_obj_new(/* ... */);
struct bpf_rb_node *res;
n->key = 10;
bpf_spin_lock(&glock);
bpf_list_push_back(&some_list, &n->l); /* n is now a non-owning ref */
res = bpf_rbtree_remove(&some_tree, &n->r, /* ... */);
if (!res)
failed_sum += n->key; /* not possible */
bpf_spin_unlock(&glock);
/* if (res) { do something useful and drop } ... */
}
The bpf_rbtree_remove in this example will always fail. Similarly to
bpf_spin_unlock, bpf_rbtree_remove is a non-owning reference
invalidation point. The verifier clobbers all non-owning refs after a
bpf_rbtree_remove call, so the "failed_sum += n->key" line will fail
verification, and in fact there's no good way to get information about
the node which failed to add after the invalidation. This patch removes
non-owning reference invalidation from bpf_rbtree_remove to allow the
above usecase to pass verification. The logic for why this is now
possible is as follows:
Before this series, bpf_rbtree_add couldn't fail and thus assumed that
its input, a non-owning reference, was in the tree. But it's easy to
construct an example where two non-owning references pointing to the same
underlying memory are acquired and passed to rbtree_remove one after
another (see rbtree_api_release_aliasing in
selftests/bpf/progs/rbtree_fail.c).
So it was necessary to clobber non-owning refs to prevent this
case and, more generally, to enforce "non-owning ref is definitely
in some collection" invariant. This series removes that invariant and
the failure / runtime checking added in this patch provide a clean way
to deal with the aliasing issue - just fail to remove.
Because the aliasing issue prevented by clobbering non-owning refs is no
longer an issue, this patch removes the invalidate_non_owning_refs
call from verifier handling of bpf_rbtree_remove. Note that
bpf_spin_unlock - the other caller of invalidate_non_owning_refs -
clobbers non-owning refs for a different reason, so its clobbering
behavior remains unchanged.
No BPF program changes are necessary for programs to remain valid as a
result of this clobbering change. A valid program before this patch
passed verification with its non-owning refs having shorter (or equal)
lifetimes due to more aggressive clobbering.
Also, update existing tests to check bpf_rbtree_remove retval for NULL
where necessary, and move rbtree_api_release_aliasing from
progs/rbtree_fail.c to progs/rbtree.c since it's now expected to pass
verification.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230415201811.343116-8-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Dave Marchevsky
|
d2dcc67df9 |
bpf: Migrate bpf_rbtree_add and bpf_list_push_{front,back} to possibly fail
Consider this code snippet:
struct node {
long key;
bpf_list_node l;
bpf_rb_node r;
bpf_refcount ref;
}
int some_bpf_prog(void *ctx)
{
struct node *n = bpf_obj_new(/*...*/), *m;
bpf_spin_lock(&glock);
bpf_rbtree_add(&some_tree, &n->r, /* ... */);
m = bpf_refcount_acquire(n);
bpf_rbtree_add(&other_tree, &m->r, /* ... */);
bpf_spin_unlock(&glock);
/* ... */
}
After bpf_refcount_acquire, n and m point to the same underlying memory,
and that node's bpf_rb_node field is being used by the some_tree insert,
so overwriting it as a result of the second insert is an error. In order
to properly support refcounted nodes, the rbtree and list insert
functions must be allowed to fail. This patch adds such support.
The kfuncs bpf_rbtree_add, bpf_list_push_{front,back} are modified to
return an int indicating success/failure, with 0 -> success, nonzero ->
failure.
bpf_obj_drop on failure
=======================
Currently the only reason an insert can fail is the example above: the
bpf_{list,rb}_node is already in use. When such a failure occurs, the
insert kfuncs will bpf_obj_drop the input node. This allows the insert
operations to logically fail without changing their verifier owning ref
behavior, namely the unconditional release_reference of the input
owning ref.
With insert that always succeeds, ownership of the node is always passed
to the collection, since the node always ends up in the collection.
With a possibly-failed insert w/ bpf_obj_drop, ownership of the node
is always passed either to the collection (success), or to bpf_obj_drop
(failure). Regardless, it's correct to continue unconditionally
releasing the input owning ref, as something is always taking ownership
from the calling program on insert.
Keeping owning ref behavior unchanged results in a nice default UX for
insert functions that can fail. If the program's reaction to a failed
insert is "fine, just get rid of this owning ref for me and let me go
on with my business", then there's no reason to check for failure since
that's default behavior. e.g.:
long important_failures = 0;
int some_bpf_prog(void *ctx)
{
struct node *n, *m, *o; /* all bpf_obj_new'd */
bpf_spin_lock(&glock);
bpf_rbtree_add(&some_tree, &n->node, /* ... */);
bpf_rbtree_add(&some_tree, &m->node, /* ... */);
if (bpf_rbtree_add(&some_tree, &o->node, /* ... */)) {
important_failures++;
}
bpf_spin_unlock(&glock);
}
If we instead chose to pass ownership back to the program on failed
insert - by returning NULL on success or an owning ref on failure -
programs would always have to do something with the returned ref on
failure. The most likely action is probably "I'll just get rid of this
owning ref and go about my business", which ideally would look like:
if (n = bpf_rbtree_add(&some_tree, &n->node, /* ... */))
bpf_obj_drop(n);
But bpf_obj_drop isn't allowed in a critical section and inserts must
occur within one, so in reality error handling would become a
hard-to-parse mess.
For refcounted nodes, we can replicate the "pass ownership back to
program on failure" logic with this patch's semantics, albeit in an ugly
way:
struct node *n = bpf_obj_new(/* ... */), *m;
bpf_spin_lock(&glock);
m = bpf_refcount_acquire(n);
if (bpf_rbtree_add(&some_tree, &n->node, /* ... */)) {
/* Do something with m */
}
bpf_spin_unlock(&glock);
bpf_obj_drop(m);
bpf_refcount_acquire is used to simulate "return owning ref on failure".
This should be an uncommon occurrence, though.
Addition of two verifier-fixup'd args to collection inserts
===========================================================
The actual bpf_obj_drop kfunc is
bpf_obj_drop_impl(void *, struct btf_struct_meta *), with bpf_obj_drop
macro populating the second arg with 0 and the verifier later filling in
the arg during insn fixup.
Because bpf_rbtree_add and bpf_list_push_{front,back} now might do
bpf_obj_drop, these kfuncs need a btf_struct_meta parameter that can be
passed to bpf_obj_drop_impl.
Similarly, because the 'node' param to those insert functions is the
bpf_{list,rb}_node within the node type, and bpf_obj_drop expects a
pointer to the beginning of the node, the insert functions need to be
able to find the beginning of the node struct. A second
verifier-populated param is necessary: the offset of {list,rb}_node within the
node type.
These two new params allow the insert kfuncs to correctly call
__bpf_obj_drop_impl:
beginning_of_node = bpf_rb_node_ptr - offset
if (already_inserted)
__bpf_obj_drop_impl(beginning_of_node, btf_struct_meta->record);
Similarly to other kfuncs with "hidden" verifier-populated params, the
insert functions are renamed with _impl prefix and a macro is provided
for common usage. For example, bpf_rbtree_add kfunc is now
bpf_rbtree_add_impl and bpf_rbtree_add is now a macro which sets
"hidden" args to 0.
Due to the two new args BPF progs will need to be recompiled to work
with the new _impl kfuncs.
This patch also rewrites the "hidden argument" explanation to more
directly say why the BPF program writer doesn't need to populate the
arguments with anything meaningful.
How does this new logic affect non-owning references?
=====================================================
Currently, non-owning refs are valid until the end of the critical
section in which they're created. We can make this guarantee because, if
a non-owning ref exists, the referent was added to some collection. The
collection will drop() its nodes when it goes away, but it can't go away
while our program is accessing it, so that's not a problem. If the
referent is removed from the collection in the same CS that it was added
in, it can't be bpf_obj_drop'd until after CS end. Those are the only
two ways to free the referent's memory and neither can happen until
after the non-owning ref's lifetime ends.
On first glance, having these collection insert functions potentially
bpf_obj_drop their input seems like it breaks the "can't be
bpf_obj_drop'd until after CS end" line of reasoning. But we care about
the memory not being _freed_ until end of CS end, and a previous patch
in the series modified bpf_obj_drop such that it doesn't free refcounted
nodes until refcount == 0. So the statement can be more accurately
rewritten as "can't be free'd until after CS end".
We can prove that this rewritten statement holds for any non-owning
reference produced by collection insert functions:
* If the input to the insert function is _not_ refcounted
* We have an owning reference to the input, and can conclude it isn't
in any collection
* Inserting a node in a collection turns owning refs into
non-owning, and since our input type isn't refcounted, there's no
way to obtain additional owning refs to the same underlying
memory
* Because our node isn't in any collection, the insert operation
cannot fail, so bpf_obj_drop will not execute
* If bpf_obj_drop is guaranteed not to execute, there's no risk of
memory being free'd
* Otherwise, the input to the insert function is refcounted
* If the insert operation fails due to the node's list_head or rb_root
already being in some collection, there was some previous successful
insert which passed refcount to the collection
* We have an owning reference to the input, it must have been
acquired via bpf_refcount_acquire, which bumped the refcount
* refcount must be >= 2 since there's a valid owning reference and the
node is already in a collection
* Insert triggering bpf_obj_drop will decr refcount to >= 1, never
resulting in a free
So although we may do bpf_obj_drop during the critical section, this
will never result in memory being free'd, and no changes to non-owning
ref logic are needed in this patch.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230415201811.343116-6-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Dave Marchevsky
|
7c50b1cb76 |
bpf: Add bpf_refcount_acquire kfunc
Currently, BPF programs can interact with the lifetime of refcounted
local kptrs in the following ways:
bpf_obj_new - Initialize refcount to 1 as part of new object creation
bpf_obj_drop - Decrement refcount and free object if it's 0
collection add - Pass ownership to the collection. No change to
refcount but collection is responsible for
bpf_obj_dropping it
In order to be able to add a refcounted local kptr to multiple
collections we need to be able to increment the refcount and acquire a
new owning reference. This patch adds a kfunc, bpf_refcount_acquire,
implementing such an operation.
bpf_refcount_acquire takes a refcounted local kptr and returns a new
owning reference to the same underlying memory as the input. The input
can be either owning or non-owning. To reinforce why this is safe,
consider the following code snippets:
struct node *n = bpf_obj_new(typeof(*n)); // A
struct node *m = bpf_refcount_acquire(n); // B
In the above snippet, n will be alive with refcount=1 after (A), and
since nothing changes that state before (B), it's obviously safe. If
n is instead added to some rbtree, we can still safely refcount_acquire
it:
struct node *n = bpf_obj_new(typeof(*n));
struct node *m;
bpf_spin_lock(&glock);
bpf_rbtree_add(&groot, &n->node, less); // A
m = bpf_refcount_acquire(n); // B
bpf_spin_unlock(&glock);
In the above snippet, after (A) n is a non-owning reference, and after
(B) m is an owning reference pointing to the same memory as n. Although
n has no ownership of that memory's lifetime, it's guaranteed to be
alive until the end of the critical section, and n would be clobbered if
we were past the end of the critical section, so it's safe to bump
refcount.
Implementation details:
* From verifier's perspective, bpf_refcount_acquire handling is similar
to bpf_obj_new and bpf_obj_drop. Like the former, it returns a new
owning reference matching input type, although like the latter, type
can be inferred from concrete kptr input. Verifier changes in
{check,fixup}_kfunc_call and check_kfunc_args are largely copied from
aforementioned functions' verifier changes.
* An exception to the above is the new KF_ARG_PTR_TO_REFCOUNTED_KPTR
arg, indicated by new "__refcounted_kptr" kfunc arg suffix. This is
necessary in order to handle both owning and non-owning input without
adding special-casing to "__alloc" arg handling. Also a convenient
place to confirm that input type has bpf_refcount field.
* The implemented kfunc is actually bpf_refcount_acquire_impl, with
'hidden' second arg that the verifier sets to the type's struct_meta
in fixup_kfunc_call.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230415201811.343116-5-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Ilya Leoshkevich
|
1cf3bfc60f |
bpf: Support 64-bit pointers to kfuncs
test_ksyms_module fails to emit a kfunc call targeting a module on s390x, because the verifier stores the difference between kfunc address and __bpf_call_base in bpf_insn.imm, which is s32, and modules are roughly (1 << 42) bytes away from the kernel on s390x. Fix by keeping BTF id in bpf_insn.imm for BPF_PSEUDO_KFUNC_CALLs, and storing the absolute address in bpf_kfunc_desc. Introduce bpf_jit_supports_far_kfunc_call() in order to limit this new behavior to the s390x JIT. Otherwise other JITs need to be modified, which is not desired. Introduce bpf_get_kfunc_addr() instead of exposing both find_kfunc_desc() and struct bpf_kfunc_desc. In addition to sorting kfuncs by imm, also sort them by offset, in order to handle conflicting imms from different modules. Do this on all architectures in order to simplify code. Factor out resolving specialized kfuncs (XPD and dynptr) from fixup_kfunc_call(). This was required in the first place, because fixup_kfunc_call() uses find_kfunc_desc(), which returns a const pointer, so it's not possible to modify kfunc addr without stripping const, which is not nice. It also removes repetition of code like: if (bpf_jit_supports_far_kfunc_call()) desc->addr = func; else insn->imm = BPF_CALL_IMM(func); and separates kfunc_desc_tab fixups from kfunc_call fixups. Suggested-by: Jiri Olsa <olsajiri@gmail.com> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20230412230632.885985-1-iii@linux.ibm.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Yafang
|
c11bd04648 |
bpf: Add preempt_count_{sub,add} into btf id deny list
The recursion check in __bpf_prog_enter* and __bpf_prog_exit*
leave preempt_count_{sub,add} unprotected. When attaching trampoline to
them we get panic as follows,
[ 867.843050] BUG: TASK stack guard page was hit at 0000000009d325cf (stack is 0000000046a46a15..00000000537e7b28)
[ 867.843064] stack guard page: 0000 [#1] PREEMPT SMP NOPTI
[ 867.843067] CPU: 8 PID: 11009 Comm: trace Kdump: loaded Not tainted 6.2.0+ #4
[ 867.843100] Call Trace:
[ 867.843101] <TASK>
[ 867.843104] asm_exc_int3+0x3a/0x40
[ 867.843108] RIP: 0010:preempt_count_sub+0x1/0xa0
[ 867.843135] __bpf_prog_enter_recur+0x17/0x90
[ 867.843148] bpf_trampoline_6442468108_0+0x2e/0x1000
[ 867.843154] ? preempt_count_sub+0x1/0xa0
[ 867.843157] preempt_count_sub+0x5/0xa0
[ 867.843159] ? migrate_enable+0xac/0xf0
[ 867.843164] __bpf_prog_exit_recur+0x2d/0x40
[ 867.843168] bpf_trampoline_6442468108_0+0x55/0x1000
...
[ 867.843788] preempt_count_sub+0x5/0xa0
[ 867.843793] ? migrate_enable+0xac/0xf0
[ 867.843829] __bpf_prog_exit_recur+0x2d/0x40
[ 867.843837] BUG: IRQ stack guard page was hit at 0000000099bd8228 (stack is 00000000b23e2bc4..000000006d95af35)
[ 867.843841] BUG: IRQ stack guard page was hit at 000000005ae07924 (stack is 00000000ffd69623..0000000014eb594c)
[ 867.843843] BUG: IRQ stack guard page was hit at 00000000028320f0 (stack is 00000000034b6438..0000000078d1bcec)
[ 867.843842] bpf_trampoline_6442468108_0+0x55/0x1000
...
That is because in __bpf_prog_exit_recur, the preempt_count_{sub,add} are
called after prog->active is decreased.
Fixing this by adding these two functions into btf ids deny list.
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Yafang <laoar.shao@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Acked-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/r/20230413025248.79764-1-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
|
Andrii Nakryiko
|
bdcab4144f |
bpf: Simplify internal verifier log interface
Simplify internal verifier log API down to bpf_vlog_init() and bpf_vlog_finalize(). The former handles input arguments validation in one place and makes it easier to change it. The latter subsumes -ENOSPC (truncation) and -EFAULT handling and simplifies both caller's code (bpf_check() and btf_parse()). For btf_parse(), this patch also makes sure that verifier log finalization happens even if there is some error condition during BTF verification process prior to normal finalization step. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Lorenz Bauer <lmb@isovalent.com> Link: https://lore.kernel.org/bpf/20230406234205.323208-14-andrii@kernel.org |
||
|
Andrii Nakryiko
|
47a71c1f9a |
bpf: Add log_true_size output field to return necessary log buffer size
Add output-only log_true_size and btf_log_true_size field to BPF_PROG_LOAD and BPF_BTF_LOAD commands, respectively. It will return the size of log buffer necessary to fit in all the log contents at specified log_level. This is very useful for BPF loader libraries like libbpf to be able to size log buffer correctly, but could be used by users directly, if necessary, as well. This patch plumbs all this through the code, taking into account actual bpf_attr size provided by user to determine if these new fields are expected by users. And if they are, set them from kernel on return. We refactory btf_parse() function to accommodate this, moving attr and uattr handling inside it. The rest is very straightforward code, which is split from the logging accounting changes in the previous patch to make it simpler to review logic vs UAPI changes. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Lorenz Bauer <lmb@isovalent.com> Link: https://lore.kernel.org/bpf/20230406234205.323208-13-andrii@kernel.org |
||
|
Andrii Nakryiko
|
8a6ca6bc55 |
bpf: Simplify logging-related error conditions handling
Move log->level == 0 check into bpf_vlog_truncated() instead of doing it explicitly. Also remove unnecessary goto in kernel/bpf/verifier.c. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Lorenz Bauer <lmb@isovalent.com> Link: https://lore.kernel.org/bpf/20230406234205.323208-11-andrii@kernel.org |
||
|
Andrii Nakryiko
|
cbedb42a0d |
bpf: Avoid incorrect -EFAULT error in BPF_LOG_KERNEL mode
If verifier log is in BPF_LOG_KERNEL mode, no log->ubuf is expected and it stays NULL throughout entire verification process. Don't erroneously return -EFAULT in such case. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Lorenz Bauer <lmb@isovalent.com> Link: https://lore.kernel.org/bpf/20230406234205.323208-10-andrii@kernel.org |
||
|
Andrii Nakryiko
|
1216640938 |
bpf: Switch BPF verifier log to be a rotating log by default
Currently, if user-supplied log buffer to collect BPF verifier log turns out to be too small to contain full log, bpf() syscall returns -ENOSPC, fails BPF program verification/load, and preserves first N-1 bytes of the verifier log (where N is the size of user-supplied buffer). This is problematic in a bunch of common scenarios, especially when working with real-world BPF programs that tend to be pretty complex as far as verification goes and require big log buffers. Typically, it's when debugging tricky cases at log level 2 (verbose). Also, when BPF program is successfully validated, log level 2 is the only way to actually see verifier state progression and all the important details. Even with log level 1, it's possible to get -ENOSPC even if the final verifier log fits in log buffer, if there is a code path that's deep enough to fill up entire log, even if normally it would be reset later on (there is a logic to chop off successfully validated portions of BPF verifier log). In short, it's not always possible to pre-size log buffer. Also, what's worse, in practice, the end of the log most often is way more important than the beginning, but verifier stops emitting log as soon as initial log buffer is filled up. This patch switches BPF verifier log behavior to effectively behave as rotating log. That is, if user-supplied log buffer turns out to be too short, verifier will keep overwriting previously written log, effectively treating user's log buffer as a ring buffer. -ENOSPC is still going to be returned at the end, to notify user that log contents was truncated, but the important last N bytes of the log would be returned, which might be all that user really needs. This consistent -ENOSPC behavior, regardless of rotating or fixed log behavior, allows to prevent backwards compatibility breakage. The only user-visible change is which portion of verifier log user ends up seeing *if buffer is too small*. Given contents of verifier log itself is not an ABI, there is no breakage due to this behavior change. Specialized tools that rely on specific contents of verifier log in -ENOSPC scenario are expected to be easily adapted to accommodate old and new behaviors. Importantly, though, to preserve good user experience and not require every user-space application to adopt to this new behavior, before exiting to user-space verifier will rotate log (in place) to make it start at the very beginning of user buffer as a continuous zero-terminated string. The contents will be a chopped off N-1 last bytes of full verifier log, of course. Given beginning of log is sometimes important as well, we add BPF_LOG_FIXED (which equals 8) flag to force old behavior, which allows tools like veristat to request first part of verifier log, if necessary. BPF_LOG_FIXED flag is also a simple and straightforward way to check if BPF verifier supports rotating behavior. On the implementation side, conceptually, it's all simple. We maintain 64-bit logical start and end positions. If we need to truncate the log, start position will be adjusted accordingly to lag end position by N bytes. We then use those logical positions to calculate their matching actual positions in user buffer and handle wrap around the end of the buffer properly. Finally, right before returning from bpf_check(), we rotate user log buffer contents in-place as necessary, to make log contents contiguous. See comments in relevant functions for details. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Lorenz Bauer <lmb@isovalent.com> Link: https://lore.kernel.org/bpf/20230406234205.323208-4-andrii@kernel.org |
||
|
Andrii Nakryiko
|
4294a0a7ab |
bpf: Split off basic BPF verifier log into separate file
kernel/bpf/verifier.c file is large and growing larger all the time. So it's good to start splitting off more or less self-contained parts into separate files to keep source code size (somewhat) somewhat under control. This patch is a one step in this direction, moving some of BPF verifier log routines into a separate kernel/bpf/log.c. Right now it's most low-level and isolated routines to append data to log, reset log to previous position, etc. Eventually we could probably move verifier state printing logic here as well, but this patch doesn't attempt to do that yet. Subsequent patches will add more logic to verifier log management, so having basics in a separate file will make sure verifier.c doesn't grow more with new changes. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Lorenz Bauer <lmb@isovalent.com> Link: https://lore.kernel.org/bpf/20230406234205.323208-2-andrii@kernel.org |
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|
Yonghong Song
|
953d9f5bea |
bpf: Improve handling of pattern '<const> <cond_op> <non_const>' in verifier
Currently, the verifier does not handle '<const> <cond_op> <non_const>' well. For example, ... 10: (79) r1 = *(u64 *)(r10 -16) ; R1_w=scalar() R10=fp0 11: (b7) r2 = 0 ; R2_w=0 12: (2d) if r2 > r1 goto pc+2 13: (b7) r0 = 0 14: (95) exit 15: (65) if r1 s> 0x1 goto pc+3 16: (0f) r0 += r1 ... At insn 12, verifier decides both true and false branch are possible, but actually only false branch is possible. Currently, the verifier already supports patterns '<non_const> <cond_op> <const>. Add support for patterns '<const> <cond_op> <non_const>' in a similar way. Also fix selftest 'verifier_bounds_mix_sign_unsign/bounds checks mixing signed and unsigned, variant 10' due to this change. Signed-off-by: Yonghong Song <yhs@fb.com> Acked-by: Dave Marchevsky <davemarchevsky@fb.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230406164505.1046801-1-yhs@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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|
Yonghong Song
|
13fbcee557 |
bpf: Improve verifier JEQ/JNE insn branch taken checking
Currently, for BPF_JEQ/BPF_JNE insn, verifier determines whether the branch is taken or not only if both operands are constants. Therefore, for the following code snippet, 0: (85) call bpf_ktime_get_ns#5 ; R0_w=scalar() 1: (a5) if r0 < 0x3 goto pc+2 ; R0_w=scalar(umin=3) 2: (b7) r2 = 2 ; R2_w=2 3: (1d) if r0 == r2 goto pc+2 6 At insn 3, since r0 is not a constant, verifier assumes both branch can be taken which may lead inproper verification failure. Add comparing umin/umax value and the constant. If the umin value is greater than the constant, or umax value is smaller than the constant, for JEQ the branch must be not-taken, and for JNE the branch must be taken. The jmp32 mode JEQ/JNE branch taken checking is also handled similarly. The following lists the veristat result w.r.t. changed number of processes insns during verification: File Program Insns (A) Insns (B) Insns (DIFF) ----------------------------------------------------- ---------------------------------------------------- --------- --------- --------------- test_cls_redirect.bpf.linked3.o cls_redirect 64980 73472 +8492 (+13.07%) test_seg6_loop.bpf.linked3.o __add_egr_x 12425 12423 -2 (-0.02%) test_tcp_hdr_options.bpf.linked3.o estab 2634 2558 -76 (-2.89%) test_parse_tcp_hdr_opt.bpf.linked3.o xdp_ingress_v6 1421 1420 -1 (-0.07%) test_parse_tcp_hdr_opt_dynptr.bpf.linked3.o xdp_ingress_v6 1238 1237 -1 (-0.08%) test_tc_dtime.bpf.linked3.o egress_fwdns_prio100 414 411 -3 (-0.72%) Mostly a small improvement but test_cls_redirect.bpf.linked3.o has a 13% regression. I checked with verifier log and found it this is due to pruning. For some JEQ/JNE branches impacted by this patch, one branch is explored and the other has state equivalence and pruned. Signed-off-by: Yonghong Song <yhs@fb.com> Acked-by: Dave Marchevsky <davemarchevsky@fb.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230406164455.1045294-1-yhs@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Alexei Starovoitov
|
afeebf9f57 |
bpf: Undo strict enforcement for walking untagged fields.
The commit |
||
|
Alexei Starovoitov
|
30ee9821f9 |
bpf: Allowlist few fields similar to __rcu tag.
Allow bpf program access cgrp->kn, mm->exe_file, skb->sk, req->sk. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230404045029.82870-7-alexei.starovoitov@gmail.com |
||
|
Alexei Starovoitov
|
add68b843f |
bpf: Refactor NULL-ness check in check_reg_type().
check_reg_type() unconditionally disallows PTR_TO_BTF_ID | PTR_MAYBE_NULL. It's problematic for helpers that allow ARG_PTR_TO_BTF_ID_OR_NULL like bpf_sk_storage_get(). Allow passing PTR_TO_BTF_ID | PTR_MAYBE_NULL into such helpers. That technically includes bpf_kptr_xchg() helper, but in practice: bpf_kptr_xchg(..., bpf_cpumask_create()); is still disallowed because bpf_cpumask_create() returns ref counted pointer with ref_obj_id > 0. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230404045029.82870-6-alexei.starovoitov@gmail.com |
||
|
Alexei Starovoitov
|
63260df139 |
bpf: Refactor btf_nested_type_is_trusted().
btf_nested_type_is_trusted() tries to find a struct member at corresponding offset.
It works for flat structures and falls apart in more complex structs with nested structs.
The offset->member search is already performed by btf_struct_walk() including nested structs.
Reuse this work and pass {field name, field btf id} into btf_nested_type_is_trusted()
instead of offset to make BTF_TYPE_SAFE*() logic more robust.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230404045029.82870-4-alexei.starovoitov@gmail.com
|
||
|
Alexei Starovoitov
|
b7e852a9ec |
bpf: Remove unused arguments from btf_struct_access().
Remove unused arguments from btf_struct_access() callback. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230404045029.82870-3-alexei.starovoitov@gmail.com |
||
|
Alexei Starovoitov
|
7d64c51328 |
bpf: Invoke btf_struct_access() callback only for writes.
Remove duplicated if (atype == BPF_READ) btf_struct_access() from btf_struct_access() callback and invoke it only for writes. This is possible to do because currently btf_struct_access() custom callback always delegates to generic btf_struct_access() helper for BPF_READ accesses. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230404045029.82870-2-alexei.starovoitov@gmail.com |
||
|
Dave Marchevsky
|
f6a6a5a976 |
bpf: Fix struct_meta lookup for bpf_obj_free_fields kfunc call
bpf_obj_drop_impl has a void return type. In check_kfunc_call, the "else
if" which sets insn_aux->kptr_struct_meta for bpf_obj_drop_impl is
surrounded by a larger if statement which checks btf_type_is_ptr. As a
result:
* The bpf_obj_drop_impl-specific code will never execute
* The btf_struct_meta input to bpf_obj_drop is always NULL
* __bpf_obj_drop_impl will always see a NULL btf_record when called
from BPF program, and won't call bpf_obj_free_fields
* program-allocated kptrs which have fields that should be cleaned up
by bpf_obj_free_fields may instead leak resources
This patch adds a btf_type_is_void branch to the larger if and moves
special handling for bpf_obj_drop_impl there, fixing the issue.
Fixes:
|
||
|
David Vernet
|
d02c48fa11 |
bpf: Make struct task_struct an RCU-safe type
struct task_struct objects are a bit interesting in terms of how their lifetime is protected by refcounts. task structs have two refcount fields: 1. refcount_t usage: Protects the memory backing the task struct. When this refcount drops to 0, the task is immediately freed, without waiting for an RCU grace period to elapse. This is the field that most callers in the kernel currently use to ensure that a task remains valid while it's being referenced, and is what's currently tracked with bpf_task_acquire() and bpf_task_release(). 2. refcount_t rcu_users: A refcount field which, when it drops to 0, schedules an RCU callback that drops a reference held on the 'usage' field above (which is acquired when the task is first created). This field therefore provides a form of RCU protection on the task by ensuring that at least one 'usage' refcount will be held until an RCU grace period has elapsed. The qualifier "a form of" is important here, as a task can remain valid after task->rcu_users has dropped to 0 and the subsequent RCU gp has elapsed. In terms of BPF, we want to use task->rcu_users to protect tasks that function as referenced kptrs, and to allow tasks stored as referenced kptrs in maps to be accessed with RCU protection. Let's first determine whether we can safely use task->rcu_users to protect tasks stored in maps. All of the bpf_task* kfuncs can only be called from tracepoint, struct_ops, or BPF_PROG_TYPE_SCHED_CLS, program types. For tracepoint and struct_ops programs, the struct task_struct passed to a program handler will always be trusted, so it will always be safe to call bpf_task_acquire() with any task passed to a program. Note, however, that we must update bpf_task_acquire() to be KF_RET_NULL, as it is possible that the task has exited by the time the program is invoked, even if the pointer is still currently valid because the main kernel holds a task->usage refcount. For BPF_PROG_TYPE_SCHED_CLS, tasks should never be passed as an argument to the any program handlers, so it should not be relevant. The second question is whether it's safe to use RCU to access a task that was acquired with bpf_task_acquire(), and stored in a map. Because bpf_task_acquire() now uses task->rcu_users, it follows that if the task is present in the map, that it must have had at least one task->rcu_users refcount by the time the current RCU cs was started. Therefore, it's safe to access that task until the end of the current RCU cs. With all that said, this patch makes struct task_struct is an RCU-protected object. In doing so, we also change bpf_task_acquire() to be KF_ACQUIRE | KF_RCU | KF_RET_NULL, and adjust any selftests as necessary. A subsequent patch will remove bpf_task_kptr_get(), and bpf_task_acquire_not_zero() respectively. Signed-off-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230331195733.699708-2-void@manifault.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
David Vernet
|
e4c2acab95 |
bpf: Handle PTR_MAYBE_NULL case in PTR_TO_BTF_ID helper call arg
When validating a helper function argument, we use check_reg_type() to
ensure that the register containing the argument is of the correct type.
When the register's base type is PTR_TO_BTF_ID, there is some
supplemental logic where we do extra checks for various combinations of
PTR_TO_BTF_ID type modifiers. For example, for PTR_TO_BTF_ID,
PTR_TO_BTF_ID | PTR_TRUSTED, and PTR_TO_BTF_ID | MEM_RCU, we call
map_kptr_match_type() for bpf_kptr_xchg() calls, and
btf_struct_ids_match() for other helper calls.
When an unhandled PTR_TO_BTF_ID type modifier combination is passed to
check_reg_type(), the verifier fails with an internal verifier error
message. This can currently be triggered by passing a PTR_MAYBE_NULL
pointer to helper functions (currently just bpf_kptr_xchg()) with an
ARG_PTR_TO_BTF_ID_OR_NULL arg type. For example, by callin
bpf_kptr_xchg(&v->kptr, bpf_cpumask_create()).
Whether or not passing a PTR_MAYBE_NULL arg to an
ARG_PTR_TO_BTF_ID_OR_NULL argument is valid is an interesting question.
In a vacuum, it seems fine. A helper function with an
ARG_PTR_TO_BTF_ID_OR_NULL arg would seem to be implying that it can
handle either a NULL or non-NULL arg, and has logic in place to detect
and gracefully handle each. This is the case for bpf_kptr_xchg(), which
of course simply does an xchg(). On the other hand, bpf_kptr_xchg() also
specifies OBJ_RELEASE, and refcounting semantics for a PTR_MAYBE_NULL
pointer is different than handling it for a NULL _OR_ non-NULL pointer.
For example, with a non-NULL arg, we should always fail if there was not
a nonzero refcount for the value in the register being passed to the
helper. For PTR_MAYBE_NULL on the other hand, it's unclear. If the
pointer is NULL it would be fine, but if it's not NULL, it would be
incorrect to load the program.
The current solution to this is to just fail if PTR_MAYBE_NULL is
passed, and to instead require programs to have a NULL check to
explicitly handle the NULL and non-NULL cases. This seems reasonable.
Not only would it possibly be quite complicated to correctly handle
PTR_MAYBE_NULL refcounting in the verifier, but it's also an arguably
odd programming pattern in general to not explicitly handle the NULL
case anyways. For example, it seems odd to not care about whether a
pointer you're passing to bpf_kptr_xchg() was successfully allocated in
a program such as the following:
private(MASK) static struct bpf_cpumask __kptr * global_mask;
SEC("tp_btf/task_newtask")
int BPF_PROG(example, struct task_struct *task, u64 clone_flags)
{
struct bpf_cpumask *prev;
/* bpf_cpumask_create() returns PTR_MAYBE_NULL */
prev = bpf_kptr_xchg(&global_mask, bpf_cpumask_create());
if (prev)
bpf_cpumask_release(prev);
return 0;
}
This patch therefore updates the verifier to explicitly check for
PTR_MAYBE_NULL in check_reg_type(), and fail gracefully if it's
observed. This isn't really "fixing" anything unsafe or incorrect. We're
just updating the verifier to fail gracefully, and explicitly handle
this pattern rather than unintentionally falling back to an internal
verifier error path. A subsequent patch will update selftests.
Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230330145203.80506-1-void@manifault.com
|
||
|
David Vernet
|
6c831c4684 |
bpf: Treat KF_RELEASE kfuncs as KF_TRUSTED_ARGS
KF_RELEASE kfuncs are not currently treated as having KF_TRUSTED_ARGS, even though they have a superset of the requirements of KF_TRUSTED_ARGS. Like KF_TRUSTED_ARGS, KF_RELEASE kfuncs require a 0-offset argument, and don't allow NULL-able arguments. Unlike KF_TRUSTED_ARGS which require _either_ an argument with ref_obj_id > 0, _or_ (ref->type & BPF_REG_TRUSTED_MODIFIERS) (and no unsafe modifiers allowed), KF_RELEASE only allows for ref_obj_id > 0. Because KF_RELEASE today doesn't automatically imply KF_TRUSTED_ARGS, some of these requirements are enforced in different ways that can make the behavior of the verifier feel unpredictable. For example, a KF_RELEASE kfunc with a NULL-able argument will currently fail in the verifier with a message like, "arg#0 is ptr_or_null_ expected ptr_ or socket" rather than "Possibly NULL pointer passed to trusted arg0". Our intention is the same, but the semantics are different due to implemenetation details that kfunc authors and BPF program writers should not need to care about. Let's make the behavior of the verifier more consistent and intuitive by having KF_RELEASE kfuncs imply the presence of KF_TRUSTED_ARGS. Our eventual goal is to have all kfuncs assume KF_TRUSTED_ARGS by default anyways, so this takes us a step in that direction. Note that it does not make sense to assume KF_TRUSTED_ARGS for all KF_ACQUIRE kfuncs. KF_ACQUIRE kfuncs can have looser semantics than KF_RELEASE, with e.g. KF_RCU | KF_RET_NULL. We may want to have KF_ACQUIRE imply KF_TRUSTED_ARGS _unless_ KF_RCU is specified, but that can be left to another patch set, and there are no such subtleties to address for KF_RELEASE. Signed-off-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230325213144.486885-4-void@manifault.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Andrii Nakryiko
|
b63cbc490e |
bpf: remember meta->iter info only for initialized iters
For iter_new() functions iterator state's slot might not be yet
initialized, in which case iter_get_spi() will return -ERANGE. This is
expected and is handled properly. But for iter_next() and iter_destroy()
cases iter slot is supposed to be initialized and correct, so -ERANGE is
not possible.
Move meta->iter.{spi,frameno} initialization into iter_next/iter_destroy
handling branch to make it more explicit that valid information will be
remembered in meta->iter block for subsequent use in process_iter_next_call(),
avoiding confusingly looking -ERANGE assignment for meta->iter.spi.
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230322232502.836171-1-andrii@kernel.org
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
|
||
|
Daniel Borkmann
|
7be14c1c90 |
bpf: Fix __reg_bound_offset 64->32 var_off subreg propagation
Xu reports that after commit |
||
JP Kobryn
|
d7ba4cc900 |
bpf: return long from bpf_map_ops funcs
This patch changes the return types of bpf_map_ops functions to long, where previously int was returned. Using long allows for bpf programs to maintain the sign bit in the absence of sign extension during situations where inlined bpf helper funcs make calls to the bpf_map_ops funcs and a negative error is returned. The definitions of the helper funcs are generated from comments in the bpf uapi header at `include/uapi/linux/bpf.h`. The return type of these helpers was previously changed from int to long in commit |
||
|
Alexei Starovoitov
|
1057d29945 |
bpf: Teach the verifier to recognize rdonly_mem as not null.
Teach the verifier to recognize PTR_TO_MEM | MEM_RDONLY as not NULL otherwise if (!bpf_ksym_exists(known_kfunc)) doesn't go through dead code elimination. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230321203854.3035-3-alexei.starovoitov@gmail.com |
||
|
Alexei Starovoitov
|
58aa2afbb1 |
bpf: Allow ld_imm64 instruction to point to kfunc.
Allow ld_imm64 insn with BPF_PSEUDO_BTF_ID to hold the address of kfunc. The ld_imm64 pointing to a valid kfunc will be seen as non-null PTR_TO_MEM by is_branch_taken() logic of the verifier, while libbpf will resolve address to unknown kfunc as ld_imm64 reg, 0 which will also be recognized by is_branch_taken() and the verifier will proceed dead code elimination. BPF programs can use this logic to detect at load time whether kfunc is present in the kernel with bpf_ksym_exists() macro that is introduced in the next patches. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org> Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20230317201920.62030-2-alexei.starovoitov@gmail.com |
||
Viktor Malik
|
bd5314f8dd |
kallsyms, bpf: Move find_kallsyms_symbol_value out of internal header
Moving find_kallsyms_symbol_value from kernel/module/internal.h to
include/linux/module.h. The reason is that internal.h is not prepared to
be included when CONFIG_MODULES=n. find_kallsyms_symbol_value is used by
kernel/bpf/verifier.c and including internal.h from it (without modules)
leads into a compilation error:
In file included from ../include/linux/container_of.h:5,
from ../include/linux/list.h:5,
from ../include/linux/timer.h:5,
from ../include/linux/workqueue.h:9,
from ../include/linux/bpf.h:10,
from ../include/linux/bpf-cgroup.h:5,
from ../kernel/bpf/verifier.c:7:
../kernel/bpf/../module/internal.h: In function 'mod_find':
../include/linux/container_of.h:20:54: error: invalid use of undefined type 'struct module'
20 | static_assert(__same_type(*(ptr), ((type *)0)->member) || \
| ^~
[...]
This patch fixes the above error.
Fixes:
|
||
Luis Gerhorst
|
082cdc69a4 |
bpf: Remove misleading spec_v1 check on var-offset stack read
For every BPF_ADD/SUB involving a pointer, adjust_ptr_min_max_vals() ensures that the resulting pointer has a constant offset if bypass_spec_v1 is false. This is ensured by calling sanitize_check_bounds() which in turn calls check_stack_access_for_ptr_arithmetic(). There, -EACCESS is returned if the register's offset is not constant, thereby rejecting the program. In summary, an unprivileged user must never be able to create stack pointers with a variable offset. That is also the case, because a respective check in check_stack_write() is missing. If they were able to create a variable-offset pointer, users could still use it in a stack-write operation to trigger unsafe speculative behavior [1]. Because unprivileged users must already be prevented from creating variable-offset stack pointers, viable options are to either remove this check (replacing it with a clarifying comment), or to turn it into a "verifier BUG"-message, also adding a similar check in check_stack_write() (for consistency, as a second-level defense). This patch implements the first option to reduce verifier bloat. This check was introduced by commit |
||
|
David Vernet
|
63d2d83d21 |
bpf: Mark struct bpf_cpumask as rcu protected
struct bpf_cpumask is a BPF-wrapper around the struct cpumask type which can be instantiated by a BPF program, and then queried as a cpumask in similar fashion to normal kernel code. The previous patch in this series makes the type fully RCU safe, so the type can be included in the rcu_protected_type BTF ID list. A subsequent patch will remove bpf_cpumask_kptr_get(), as it's no longer useful now that we can just treat the type as RCU safe by default and do our own if check. Signed-off-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230316054028.88924-3-void@manifault.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Viktor Malik
|
31bf1dbccf |
bpf: Fix attaching fentry/fexit/fmod_ret/lsm to modules
This resolves two problems with attachment of fentry/fexit/fmod_ret/lsm to functions located in modules: 1. The verifier tries to find the address to attach to in kallsyms. This is always done by searching the entire kallsyms, not respecting the module in which the function is located. Such approach causes an incorrect attachment address to be computed if the function to attach to is shadowed by a function of the same name located earlier in kallsyms. 2. If the address to attach to is located in a module, the module reference is only acquired in register_fentry. If the module is unloaded between the place where the address is found (bpf_check_attach_target in the verifier) and register_fentry, it is possible that another module is loaded to the same address which may lead to potential errors. Since the attachment must contain the BTF of the program to attach to, we extract the module from it and search for the function address in the correct module (resolving problem no. 1). Then, the module reference is taken directly in bpf_check_attach_target and stored in the bpf program (in bpf_prog_aux). The reference is only released when the program is unloaded (resolving problem no. 2). Signed-off-by: Viktor Malik <vmalik@redhat.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Link: https://lore.kernel.org/r/3f6a9d8ae850532b5ef864ef16327b0f7a669063.1678432753.git.vmalik@redhat.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
|
Alexei Starovoitov
|
3e30be4288 |
bpf: Allow helpers access trusted PTR_TO_BTF_ID.
The verifier rejects the code: bpf_strncmp(task->comm, 16, "my_task"); with the message: 16: (85) call bpf_strncmp#182 R1 type=trusted_ptr_ expected=fp, pkt, pkt_meta, map_key, map_value, mem, ringbuf_mem, buf Teach the verifier that such access pattern is safe. Do not allow untrusted and legacy ptr_to_btf_id to be passed into helpers. Reported-by: David Vernet <void@manifault.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230313235845.61029-3-alexei.starovoitov@gmail.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> |
||
|
Andrii Nakryiko
|
34f0677e7a |
bpf: fix precision propagation verbose logging
Fix wrong order of frame index vs register/slot index in precision
propagation verbose (level 2) output. It's wrong and very confusing as is.
Fixes:
|
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|
Dave Marchevsky
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738c96d5e2 |
bpf: Allow local kptrs to be exchanged via bpf_kptr_xchg
The previous patch added necessary plumbing for verifier and runtime to know what to do with non-kernel PTR_TO_BTF_IDs in map values, but didn't provide any way to get such local kptrs into a map value. This patch modifies verifier handling of bpf_kptr_xchg to allow MEM_ALLOC kptr types. check_reg_type is modified accept MEM_ALLOC-flagged input to bpf_kptr_xchg despite such types not being in btf_ptr_types. This could have been done with a MAYBE_MEM_ALLOC equivalent to MAYBE_NULL, but bpf_kptr_xchg is the only helper that I can forsee using MAYBE_MEM_ALLOC, so keep it special-cased for now. The verifier tags bpf_kptr_xchg retval MEM_ALLOC if and only if the BTF associated with the retval is not kernel BTF. Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> Link: https://lore.kernel.org/r/20230310230743.2320707-3-davemarchevsky@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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Dave Marchevsky
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b32a5dae44 |
bpf: verifier: Rename kernel_type_name helper to btf_type_name
kernel_type_name was introduced in commit |