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authorDavid Vernet <void@manifault.com>2023-10-09 11:14:13 -0500
committerDaniel Borkmann <daniel@iogearbox.net>2023-10-09 23:10:58 +0200
commit829955981c557c7fc7416581c4cd68a8a0c28620 (patch)
tree80b95778675492d06e075316b2aa066b61cb184c /kernel
parenta12bbb3cccf03b12847de0f7a6772127f90936ac (diff)
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
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c0c7d137066a..873ade146f3d 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;