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

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Date:   Sun, 31 May 2020 10:28:39 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, kernel-team@...udflare.com,
        Lorenz Bauer <lmb@...udflare.com>
Subject: [PATCH bpf-next v2 05/12] bpf, cgroup: Return ENOLINK for auto-detached links on update

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>
---
 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