f79efcb007
[ Upstream commit cd17d38f8b28f808c368121041c0a4fa91757e0d ]
Currently, when checking stack memory accessed by helper calls,
for spills, only PTR_TO_BTF_ID and SCALAR_VALUE are
allowed.
Song discovered an issue where the below bpf program
int dump_task(struct bpf_iter__task *ctx)
{
struct seq_file *seq = ctx->meta->seq;
static char[] info = "abc";
BPF_SEQ_PRINTF(seq, "%s\n", info);
return 0;
}
may cause a verifier failure.
The verifier output looks like:
; struct seq_file *seq = ctx->meta->seq;
1: (79) r1 = *(u64 *)(r1 +0)
; BPF_SEQ_PRINTF(seq, "%s\n", info);
2: (18) r2 = 0xffff9054400f6000
4: (7b) *(u64 *)(r10 -8) = r2
5: (bf) r4 = r10
;
6: (07) r4 += -8
; BPF_SEQ_PRINTF(seq, "%s\n", info);
7: (18) r2 = 0xffff9054400fe000
9: (b4) w3 = 4
10: (b4) w5 = 8
11: (85) call bpf_seq_printf#126
R1_w=ptr_seq_file(id=0,off=0,imm=0) R2_w=map_value(id=0,off=0,ks=4,vs=4,imm=0)
R3_w=inv4 R4_w=fp-8 R5_w=inv8 R10=fp0 fp-8_w=map_value
last_idx 11 first_idx 0
regs=8 stack=0 before 10: (b4) w5 = 8
regs=8 stack=0 before 9: (b4) w3 = 4
invalid indirect read from stack off -8+0 size 8
Basically, the verifier complains the map_value pointer at "fp-8" location.
To fix the issue, if env->allow_ptr_leaks is true, let us also permit
pointers on the stack to be accessible by the helper.
Reported-by: Song Liu <songliubraving@fb.com>
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201210013349.943719-1-yhs@fb.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.