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net: unix: non blocking recvmsg() should not return -EINTR 

[ Upstream commit de1443916791d75fdd26becb116898277bb0273f ]

Some applications didn't expect recvmsg() on a non blocking socket
could return -EINTR. This possibility was added as a side effect
of commit b3ca9b02b0 ("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: b3ca9b02b0 ("net: fix multithreaded signal handling in unix recv routines")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet 2014-03-25 18:42:27 -07:00 committed by Greg Kroah-Hartman
parent 098c9960de
commit d7fc329bf0
1 changed files with 12 additions and 5 deletions
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17
net/unix/af_unix.c
View File

@ -1787,8 +1787,11 @@ static int unix_dgram_recvmsg(struct kiocb *iocb, struct socket *sock,
goto out; goto out;
err = mutex_lock_interruptible(&u->readlock); err = mutex_lock_interruptible(&u->readlock);
if (err) { if (unlikely(err)) {
err = sock_intr_errno(sock_rcvtimeo(sk, noblock)); /* 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; goto out;
} }
@ -1910,6 +1913,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
struct unix_sock *u = unix_sk(sk); struct unix_sock *u = unix_sk(sk);
struct sockaddr_un *sunaddr = msg->msg_name; struct sockaddr_un *sunaddr = msg->msg_name;
int copied = 0; int copied = 0;
int noblock = flags & MSG_DONTWAIT;
int check_creds = 0; int check_creds = 0;
int target; int target;
int err = 0; int err = 0;
@ -1925,7 +1929,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
goto out; goto out;
target = sock_rcvlowat(sk, flags&MSG_WAITALL, size); 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 /* Lock the socket to prevent queue disordering
* while sleeps in memcpy_tomsg * while sleeps in memcpy_tomsg
@ -1937,8 +1941,11 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
} }
err = mutex_lock_interruptible(&u->readlock); err = mutex_lock_interruptible(&u->readlock);
if (err) { if (unlikely(err)) {
err = sock_intr_errno(timeo); /* 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; goto out;
} }