Commit 22e5751b authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Paolo Abeni
Browse files

af_unix: Don't use spin_lock_nested() 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, two sk_peer_locks are held there; one is client's and another
is listener's.

However, the latter is not needed because we hold the listner's
unix_state_lock() there and unix_listen() cannot update the cred
concurrently.

Let's drop the unnecessary spin_lock() and use the bare spin_lock()
for the client to protect concurrent read by getsockopt(SO_PEERCRED).

Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent e4bd881d

net/unix/af_unix.c

+3 −10
Original line number Diff line number Diff line
@@ -772,19 +772,12 @@ static void update_peercred(struct sock *sk) 


static void copy_peercred(struct sock *sk, struct sock *peersk)

{

	if (sk < peersk) {

		spin_lock(&sk->sk_peer_lock);

		spin_lock_nested(&peersk->sk_peer_lock, SINGLE_DEPTH_NESTING);

	} else {

		spin_lock(&peersk->sk_peer_lock);

		spin_lock_nested(&sk->sk_peer_lock, SINGLE_DEPTH_NESTING);

	}

	lockdep_assert_held(&unix_sk(peersk)->lock);



	spin_lock(&sk->sk_peer_lock);

	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);

}



static int unix_listen(struct socket *sock, int backlog)