iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

bpf: Move PTR_TO_STACK alignment check to process_dynptr_func

Browse Source 
After previous commit, we are minimizing helper specific assumptions
from check_func_arg_reg_off, making it generic, and offloading checks
for a specific argument type to their respective functions called after
check_func_arg_reg_off has been called.

This allows relying on a consistent set of guarantees after that call
and then relying on them in code that deals with registers for each
argument type later. This is in line with how process_spin_lock,
process_timer_func, process_kptr_func check reg->var_off to be constant.
The same reasoning is used here to move the alignment check into
process_dynptr_func. Note that it also needs to check for constant
var_off, and accumulate the constant var_off when computing the spi in
get_spi, but that fix will come in later changes.

Acked-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20221207204141.308952-6-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2022-12-08 02:11:39 +05:30 committed by Alexei Starovoitov
parent 184c9bdb8f
commit f6ee298fa1
1 changed files with 8 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
kernel/bpf/verifier.c
View File

@ -5932,6 +5932,14 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
verbose(env, "verifier internal error: misconfigured dynptr helper type flags\n");
return -EFAULT;
}
/* CONST_PTR_TO_DYNPTR already has fixed and var_off as 0 due to
* check_func_arg_reg_off's logic. We only need to check offset
* alignment for PTR_TO_STACK.
*/
if (reg->type == PTR_TO_STACK && (reg->off % BPF_REG_SIZE)) {
verbose(env, "cannot pass in dynptr at an offset=%d\n", reg->off);
return -EINVAL;
}
/* MEM_UNINIT - Points to memory that is an appropriate candidate for
* constructing a mutable bpf_dynptr object.
*
@ -6301,11 +6309,6 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
switch (type) {
/* Pointer types where both fixed and variable offset is explicitly allowed: */
case PTR_TO_STACK:
if (arg_type_is_dynptr(arg_type) && reg->off % BPF_REG_SIZE) {
verbose(env, "cannot pass in dynptr at an offset\n");
return -EINVAL;
}
fallthrough;
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
case PTR_TO_MAP_KEY: