[PATCH 3.8 149/166] net: unix: allow set_peek_off to fail

Kamal Mostafa
2014-01-15T21:52:43Z

From: Sasha Levin <sasha.levin@oracle.com>

[ Upstream commit 12663bfc97c8b3fdb292428105dd92d563164050 ]

unix_dgram_recvmsg() will hold the readlock of the socket until recv
is complete.

In the same time, we may try to setsockopt(SO_PEEK_OFF) which will hang until
unix_dgram_recvmsg() will complete (which can take a while) without allowing
us to break out of it, triggering a hung task spew.

Instead, allow set_peek_off to fail, this way userspace will not hang.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
include/linux/net.h | 2 +-
net/core/sock.c | 2 +-
net/unix/af_unix.c | 8 ++++++--
3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/net.h b/include/linux/net.h
index 5ea38d9..f6dc1f5 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -180,7 +180,7 @@ struct proto_ops {
int offset, size_t size, int flags);
ssize_t (*splice_read)(struct socket *sock, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len, unsigned int flags);
- void (*set_peek_off)(struct sock *sk, int val);
+ int (*set_peek_off)(struct sock *sk, int val);
};

#define DECLARE_SOCKADDR(type, dst, src) \
diff --git a/net/core/sock.c b/net/core/sock.c
index fc0d751..7367c05 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -886,7 +886,7 @@ set_rcvbuf:

case SO_PEEK_OFF:
if (sock->ops->set_peek_off)
- sock->ops->set_peek_off(sk, val);
+ ret = sock->ops->set_peek_off(sk, val);
else
ret = -EOPNOTSUPP;
break;
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 6cc5803..499efb7 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -531,13 +531,17 @@ static int unix_seqpacket_sendmsg(struct kiocb *, struct socket *,
static int unix_seqpacket_recvmsg(struct kiocb *, struct socket *,
struct msghdr *, size_t, int);

-static void unix_set_peek_off(struct sock *sk, int val)
+static int unix_set_peek_off(struct sock *sk, int val)
{
struct unix_sock *u = unix_sk(sk);

- mutex_lock(&u->readlock);
+ if (mutex_lock_interruptible(&u->readlock))
+ return -EINTR;
+
sk->sk_peek_off = val;
mutex_unlock(&u->readlock);
+
+ return 0;
}

--
1.8.3.2