af_unix: Remove put_pid()/put_cred() in copy_peercred().

When (AF_UNIX, SOCK_STREAM) socket connect()s to a listening socket,
the listener's sk_peer_pid/sk_peer_cred are copied to the client in
copy_peercred().

Then, the client's sk_peer_pid and sk_peer_cred are always NULL, so
we need not call put_pid() and put_cred() there.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/unix/af_unix.c

@@ -772,9 +772,6 @@ static void update_peercred(struct sock *sk)
 
 static void copy_peercred(struct sock *sk, struct sock *peersk)
 {
-	const struct cred *old_cred;
-	struct pid *old_pid;
-
 	if (sk < peersk) {
 		spin_lock(&sk->sk_peer_lock);
 		spin_lock_nested(&peersk->sk_peer_lock, SINGLE_DEPTH_NESTING);
@@ -782,16 +779,12 @@ static void copy_peercred(struct sock *sk, struct sock *peersk)
 		spin_lock(&peersk->sk_peer_lock);
 		spin_lock_nested(&sk->sk_peer_lock, SINGLE_DEPTH_NESTING);
 	}
-	old_pid = sk->sk_peer_pid;
-	old_cred = sk->sk_peer_cred;
+
 	sk->sk_peer_pid  = get_pid(peersk->sk_peer_pid);
 	sk->sk_peer_cred = get_cred(peersk->sk_peer_cred);
 
 	spin_unlock(&sk->sk_peer_lock);
 	spin_unlock(&peersk->sk_peer_lock);
-
-	put_pid(old_pid);
-	put_cred(old_cred);
 }
 
 static int unix_listen(struct socket *sock, int backlog)