[PATCH 4.9 34/49] vsock: fix locking in vsock_shutdown()

[Greg Kroah-Hartman]

From: Stefano Garzarella <sgarzare@xxxxxxxxxx>

commit 1c5fae9c9a092574398a17facc31c533791ef232 upstream.

In vsock_shutdown() we touched some socket fields without holding the
socket lock, such as 'state' and 'sk_flags'.

Also, after the introduction of multi-transport, we are accessing
'vsk->transport' in vsock_send_shutdown() without holding the lock
and this call can be made while the connection is in progress, so
the transport can change in the meantime.

To avoid issues, we hold the socket lock when we enter in
vsock_shutdown() and release it when we leave.

Among the transports that implement the 'shutdown' callback, only
hyperv_transport acquired the lock. Since the caller now holds it,
we no longer take it.

Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/vmw_vsock/af_vsock.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -830,10 +830,12 @@ static int vsock_shutdown(struct socket
 	 */
 
 	sk = sock->sk;
+
+	lock_sock(sk);
 	if (sock->state == SS_UNCONNECTED) {
 		err = -ENOTCONN;
 		if (sk->sk_type == SOCK_STREAM)
-			return err;
+			goto out;
 	} else {
 		sock->state = SS_DISCONNECTING;
 		err = 0;
@@ -842,10 +844,8 @@ static int vsock_shutdown(struct socket
 	/* Receive and send shutdowns are treated alike. */
 	mode = mode & (RCV_SHUTDOWN | SEND_SHUTDOWN);
 	if (mode) {
-		lock_sock(sk);
 		sk->sk_shutdown |= mode;
 		sk->sk_state_change(sk);
-		release_sock(sk);
 
 		if (sk->sk_type == SOCK_STREAM) {
 			sock_reset_flag(sk, SOCK_DONE);
@@ -853,6 +853,8 @@ static int vsock_shutdown(struct socket
 		}
 	}
 
+out:
+	release_sock(sk);
 	return err;
 }