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

[Jakub Sitnicki]

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 <l...@cloudflare.com>
Signed-off-by: Jakub Sitnicki <ja...@cloudflare.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