linux-kernel - Re: [PATCH bpf-next v4 1/4] bpf: Fix an off-by-one error in check_indirect

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Message-ID: <aWdwGKLsL7G7IQ3z@mail.gmail.com>
Date: Wed, 14 Jan 2026 10:29:44 +0000
From: Anton Protopopov <a.s.protopopov@...il.com>
To: Xu Kuohai <xukuohai@...weicloud.com>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Yonghong Song <yonghong.song@...ux.dev>,
	Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH bpf-next v4 1/4] bpf: Fix an off-by-one error in
 check_indirect_jump

On 26/01/14 05:39PM, Xu Kuohai wrote:
> From: Xu Kuohai <xukuohai@...wei.com>
> 
> Fix an off-by-one error in check_indirect_jump() that skips the last
> element returned by copy_insn_array_uniq().
> 
> Fixes: 493d9e0d6083 ("bpf, x86: add support for indirect jumps")
> Signed-off-by: Xu Kuohai <xukuohai@...wei.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 faa1ecc1fe9d..22605d9e0ffa 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -20336,7 +20336,7 @@ static int check_indirect_jump(struct bpf_verifier_env *env, struct bpf_insn *in
>  		return -EINVAL;
>  	}
>  
> -	for (i = 0; i < n - 1; i++) {
> +	for (i = 0; i < n; i++) {
>  		other_branch = push_stack(env, env->gotox_tmp_buf->items[i],
>  					  env->insn_idx, env->cur_state->speculative);
>  		if (IS_ERR(other_branch))
> -- 
> 2.47.3

Nack, the last state doesn't require a push_stack() call, it is
verified directly under this loop. Instead of this patch, just
add another call to mark_indirect_target().