af_unix: Avoid socket->sk NULL OOPS in stream connect security hooks.
unix_release() can asynchornously set socket->sk to NULL, and it does so without holding the unix_state_lock() on "other" during stream connects. However, the reverse mapping, sk->sk_socket, is only transitioned to NULL under the unix_state_lock(). Therefore make the security hooks follow the reverse mapping instead of the forward mapping. Reported-by: Jeremy Fitzhardinge <firstname.lastname@example.org> Reported-by: Linus Torvalds <email@example.com> Signed-off-by: David S. Miller <firstname.lastname@example.org>