Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 5456f09a authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

af_unix: fix unix_dgram_poll() behavior for EPOLLOUT event 



Alban Crequy reported a problem with connected dgram af_unix sockets and
provided a test program. epoll() would miss to send an EPOLLOUT event
when a thread unqueues a packet from the other peer, making its receive
queue not full.

This is because unix_dgram_poll() fails to call sock_poll_wait(file,
&unix_sk(other)->peer_wait, wait);
if the socket is not writeable at the time epoll_ctl(ADD) is called.

We must call sock_poll_wait(), regardless of 'writable' status, so that
epoll can be notified later of states changes.

Misc: avoids testing twice (sk->sk_shutdown & RCV_SHUTDOWN)

Reported-by: default avatarAlban Crequy <alban.crequy@collabora.co.uk>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Acked-by: default avatarDavide Libenzi <davidel@xmailserver.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 67426b75

net/unix/af_unix.c

+9 −15
Original line number Diff line number Diff line
@@ -2074,13 +2074,12 @@ static unsigned int unix_dgram_poll(struct file *file, struct socket *sock, 
	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))

		mask |= POLLERR;

	if (sk->sk_shutdown & RCV_SHUTDOWN)

		mask |= POLLRDHUP;

		mask |= POLLRDHUP | POLLIN | POLLRDNORM;

	if (sk->sk_shutdown == SHUTDOWN_MASK)

		mask |= POLLHUP;



	/* readable? */

	if (!skb_queue_empty(&sk->sk_receive_queue) ||

	    (sk->sk_shutdown & RCV_SHUTDOWN))

	if (!skb_queue_empty(&sk->sk_receive_queue))

		mask |= POLLIN | POLLRDNORM;



	/* Connection-based need to check for termination and startup */
@@ -2092,21 +2091,16 @@ static unsigned int unix_dgram_poll(struct file *file, struct socket *sock, 
			return mask;

	}



	/* writable? */

	writable = unix_writable(sk);

	if (writable) {

	other = unix_peer_get(sk);

	if (other) {

		if (unix_peer(other) != sk) {

				sock_poll_wait(file, &unix_sk(other)->peer_wait,

					  wait);

			sock_poll_wait(file, &unix_sk(other)->peer_wait, wait);

			if (unix_recvq_full(other))

				writable = 0;

		}



		sock_put(other);

	}

	}



	if (writable)

		mask |= POLLOUT | POLLWRNORM | POLLWRBAND;