netdev - Re: [PATCH bpf-next v2 05/12] bpf, cgroup: Return ENOLINK for auto-detached links on update

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Date:   Mon, 1 Jun 2020 15:31:05 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jakub Sitnicki <jakub@...udflare.com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        kernel-team@...udflare.com, Lorenz Bauer <lmb@...udflare.com>
Subject: Re: [PATCH bpf-next v2 05/12] bpf, cgroup: Return ENOLINK for
 auto-detached links on update

On Sun, May 31, 2020 at 1:29 AM Jakub Sitnicki <jakub@...udflare.com> wrote:
>
> Failure to update a bpf_link because it has been auto-detached by a dying
> cgroup currently results in EINVAL error, even though the arguments passed
> to bpf() syscall are not wrong.
>
> bpf_links attaching to netns in this case will return ENOLINK, which
> carries the message that the link is no longer attached to anything.
>
> Change cgroup bpf_links to do the same to keep the uAPI errors consistent.
>
> Fixes: 0c991ebc8c69 ("bpf: Implement bpf_prog replacement for an active bpf_cgroup_link")
> Suggested-by: Lorenz Bauer <lmb@...udflare.com>
> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
> ---

Looks good, thanks!

Acked-by: Andrii Nakryiko <andriin@...com>

>  kernel/bpf/cgroup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index 5c0e964105ac..fdf7836750a3 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -595,7 +595,7 @@ static int cgroup_bpf_replace(struct bpf_link *link, struct bpf_prog *new_prog,
>         mutex_lock(&cgroup_mutex);
>         /* link might have been auto-released by dying cgroup, so fail */
>         if (!cg_link->cgroup) {
> -               ret = -EINVAL;
> +               ret = -ENOLINK;
>                 goto out_unlock;
>         }
>         if (old_prog && link->prog != old_prog) {
> --
> 2.25.4
>