Re: [PATCH bpf 3/4] bpf: Improve ctx access verifier error message

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2025-08-01 at 11:49 +0200, Paul Chaignon wrote:
> We've already had two "error during ctx access conversion" warnings
> triggered by syzkaller. Let's improve the error message by dumping the
> cnt variable so that we can more easily differentiate between the
> different error cases.
> 
> Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
> ---

Acked-by: Eduard Zingerman <eddyz87@gmail.com>

>  kernel/bpf/verifier.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 399f03e62508..0806295945e4 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -21445,7 +21445,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
>  					 &target_size);
>  		if (cnt == 0 || cnt >= INSN_BUF_SIZE ||
>  		    (ctx_field_size && !target_size)) {
> -			verifier_bug(env, "error during ctx access conversion");
> +			verifier_bug(env, "error during ctx access conversion (%d)", cnt);

Nit: maybe print the rest of the fields as well?

>  			return -EFAULT;
>  		}
>