apparmor: fix race in unix socket mediation when peer_path is used

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix race in unix socket mediation when peer_path is used The holding a reference to the peer_sk is not enough to ensure access to the peer sk path. Accessing the path outside of the state lock allows for a race with unix_release_sock(). Fix this by taking the state lock and getting a reference to the path under lock. Ideally for connected sockets we would cache this information so we don't have to take the lock here. But for now just fix the race.