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Commit de144391 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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net: unix: non blocking recvmsg() should not return -EINTR 



Some applications didn't expect recvmsg() on a non blocking socket
could return -EINTR. This possibility was added as a side effect
of commit b3ca9b02 ("net: fix multithreaded signal handling in
unix recv routines").

To hit this bug, you need to be a bit unlucky, as the u->readlock
mutex is usually held for very small periods.

Fixes: b3ca9b02 ("net: fix multithreaded signal handling in unix recv routines")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dc0fe58f

net/unix/af_unix.c

+12 −5
Original line number Diff line number Diff line
@@ -1787,8 +1787,11 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock, 
		goto out;



	err = mutex_lock_interruptible(&u->readlock);

	if (err) {

		err = sock_intr_errno(sock_rcvtimeo(sk, noblock));

	if (unlikely(err)) {

		/* recvmsg() in non blocking mode is supposed to return -EAGAIN

		 * sk_rcvtimeo is not honored by mutex_lock_interruptible()

		 */

		err = noblock ? -EAGAIN : -ERESTARTSYS;

		goto out;

	}
@@ -1913,6 +1916,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, 
	struct unix_sock *u = unix_sk(sk);

	DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr, msg->msg_name);

	int copied = 0;

	int noblock = flags & MSG_DONTWAIT;

	int check_creds = 0;

	int target;

	int err = 0;
@@ -1928,7 +1932,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, 
		goto out;



	target = sock_rcvlowat(sk, flags&MSG_WAITALL, size);

	timeo = sock_rcvtimeo(sk, flags&MSG_DONTWAIT);

	timeo = sock_rcvtimeo(sk, noblock);



	/* Lock the socket to prevent queue disordering

	 * while sleeps in memcpy_tomsg
@@ -1940,8 +1944,11 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, 
	}



	err = mutex_lock_interruptible(&u->readlock);

	if (err) {

		err = sock_intr_errno(timeo);

	if (unlikely(err)) {

		/* recvmsg() in non blocking mode is supposed to return -EAGAIN

		 * sk_rcvtimeo is not honored by mutex_lock_interruptible()

		 */

		err = noblock ? -EAGAIN : -ERESTARTSYS;

		goto out;

	}