diff options
| author | Yonghong Song <yonghong.song@linux.dev> | 2023-11-30 18:46:40 -0800 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2023-12-01 15:41:50 -0800 |
| commit | dfce9cb3140592b886838e06f3e0c25fea2a9cae (patch) | |
| tree | e3e3996806c2f48fb223715059d780f66af89db6 /kernel/bpf/core.c | |
| parent | 830139e7b6911266a84a77e1f18abf758995cc89 (diff) | |
bpf: Fix a verifier bug due to incorrect branch offset comparison with cpu=v4
Bpf cpu=v4 support is introduced in [1] and Commit 4cd58e9af8b9
("bpf: Support new 32bit offset jmp instruction") added support for new
32bit offset jmp instruction. Unfortunately, in function
bpf_adj_delta_to_off(), for new branch insn with 32bit offset, the offset
(plus/minor a small delta) compares to 16-bit offset bound
[S16_MIN, S16_MAX], which caused the following verification failure:
$ ./test_progs-cpuv4 -t verif_scale_pyperf180
...
insn 10 cannot be patched due to 16-bit range
...
libbpf: failed to load object 'pyperf180.bpf.o'
scale_test:FAIL:expect_success unexpected error: -12 (errno 12)
#405 verif_scale_pyperf180:FAIL
Note that due to recent llvm18 development, the patch [2] (already applied
in bpf-next) needs to be applied to bpf tree for testing purpose.
The fix is rather simple. For 32bit offset branch insn, the adjusted
offset compares to [S32_MIN, S32_MAX] and then verification succeeded.
[1] https://lore.kernel.org/all/20230728011143.3710005-1-yonghong.song@linux.dev
[2] https://lore.kernel.org/bpf/20231110193644.3130906-1-yonghong.song@linux.dev
Fixes: 4cd58e9af8b9 ("bpf: Support new 32bit offset jmp instruction")
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20231201024640.3417057-1-yonghong.song@linux.dev
Diffstat (limited to 'kernel/bpf/core.c')
| -rw-r--r-- | kernel/bpf/core.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index cd3afe57ece3..fe254ae035fe 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -371,14 +371,18 @@ static int bpf_adj_delta_to_imm(struct bpf_insn *insn, u32 pos, s32 end_old, static int bpf_adj_delta_to_off(struct bpf_insn *insn, u32 pos, s32 end_old, s32 end_new, s32 curr, const bool probe_pass) { - const s32 off_min = S16_MIN, off_max = S16_MAX; + s64 off_min, off_max, off; s32 delta = end_new - end_old; - s32 off; - if (insn->code == (BPF_JMP32 | BPF_JA)) + if (insn->code == (BPF_JMP32 | BPF_JA)) { off = insn->imm; - else + off_min = S32_MIN; + off_max = S32_MAX; + } else { off = insn->off; + off_min = S16_MIN; + off_max = S16_MAX; + } if (curr < pos && curr + off + 1 >= end_old) off += delta; |