Commit fd0a109a0f6b ("net, pidfs: prepare for handing out pidfds for
reaped sk->sk_peer_pid") inserted a `prepare_peercred()` call between
`err = -EINVAL` and the socket-state check in `unix_listen()`. Since
`prepare_peercred()` leaves `err` at 0 on success, `listen()` on an
AF_UNIX socket that is not in `TCP_CLOSE` or `TCP_LISTEN` state (e.g.
one that is already connected) now silently returns success without
doing anything, instead of failing with `EINVAL` as it did before.

Fixes: fd0a109a0f6b ("net, pidfs: prepare for handing out pidfds for reaped sk->sk_peer_pid")
Signed-off-by: John Ericson <redacted>

Reviewed-by: Christian Brauner (Amutable) <brauner@kernel.org>

-- 
Christian Brauner [off-list ref]