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

[Anton Protopopov <a.s.protopopov@gmail.com>]

On 26/01/14 05:39PM, Xu Kuohai wrote:
> From: Xu Kuohai <xukuohai@huawei.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@huawei.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().