[bpf-next,v2,7/7] bpf: print full verifier states on infinite loop detection

Commit Message

Eduard Zingerman Oct. 22, 2023, 1:08 a.m. UTC

Additional logging in is_state_visited(): if infinite loop is detected
print full verifier state for both current and equivalent states.

Signed-off-by: Eduard Zingerman <[e-mail]>
---
 kernel/bpf/verifier.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Andrii Nakryiko Oct. 22, 2023, 4:28 a.m. UTC | #1

On Sat, Oct 21, 2023 at 6:08 PM Eduard Zingerman <[e-mail]> wrote:
>
> Additional logging in is_state_visited(): if infinite loop is detected
> print full verifier state for both current and equivalent states.
>
> Signed-off-by: Eduard Zingerman <[e-mail]>
> ---
>  kernel/bpf/verifier.c | 4 ++++
>  1 file changed, 4 insertions(+)
>

Great, thanks!

Acked-by: Andrii Nakryiko <[e-mail]>

> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index baf31b61b3ff..a91aa8638dba 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -16927,6 +16927,10 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
>                             !iter_active_depths_differ(&sl->state, cur)) {
>                                 verbose_linfo(env, insn_idx, "; ");
>                                 verbose(env, "infinite loop detected at insn %d\n", insn_idx);
> +                               verbose(env, "cur state:");
> +                               print_verifier_state(env, cur->frame[cur->curframe], true);
> +                               verbose(env, "old state:");
> +                               print_verifier_state(env, sl->state.frame[cur->curframe], true);
>                                 return -EINVAL;
>                         }
>                         /* if the verifier is processing a loop, avoid adding new state
> --
> 2.42.0
>

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index baf31b61b3ff..a91aa8638dba 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -16927,6 +16927,10 @@  static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
 			    !iter_active_depths_differ(&sl->state, cur)) {
 				verbose_linfo(env, insn_idx, "; ");
 				verbose(env, "infinite loop detected at insn %d\n", insn_idx);
+				verbose(env, "cur state:");
+				print_verifier_state(env, cur->frame[cur->curframe], true);
+				verbose(env, "old state:");
+				print_verifier_state(env, sl->state.frame[cur->curframe], true);
 				return -EINVAL;
 			}
 			/* if the verifier is processing a loop, avoid adding new state