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| author | David Vernet <void@manifault.com> | 2023-10-09 11:14:13 -0500 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-10-09 23:10:58 +0200 |
| commit | 829955981c557c7fc7416581c4cd68a8a0c28620 (patch) | |
| tree | 80b95778675492d06e075316b2aa066b61cb184c | |
| parent | a12bbb3cccf03b12847de0f7a6772127f90936ac (diff) | |
| download | linux-829955981c557c7fc7416581c4cd68a8a0c28620.tar.gz | |
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: bfc6bb74e4f1 ("bpf: Implement verifier support for validation of async callbacks.")
Signed-off-by: David Vernet <void@manifault.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20231009161414.235829-1-void@manifault.com
| -rw-r--r-- | kernel/bpf/verifier.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c0c7d137066ac8..873ade146f3deb 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -14479,7 +14479,7 @@ static int check_return_code(struct bpf_verifier_env *env) struct tnum enforce_attach_type_range = tnum_unknown; const struct bpf_prog *prog = env->prog; struct bpf_reg_state *reg; - struct tnum range = tnum_range(0, 1); + struct tnum range = tnum_range(0, 1), const_0 = tnum_const(0); enum bpf_prog_type prog_type = resolve_prog_type(env->prog); int err; struct bpf_func_state *frame = env->cur_state->frame[0]; @@ -14527,8 +14527,8 @@ static int check_return_code(struct bpf_verifier_env *env) return -EINVAL; } - if (!tnum_in(tnum_const(0), reg->var_off)) { - verbose_invalid_scalar(env, reg, &range, "async callback", "R0"); + if (!tnum_in(const_0, reg->var_off)) { + verbose_invalid_scalar(env, reg, &const_0, "async callback", "R0"); return -EINVAL; } return 0; |