vsock/virtio: free queued packets when closing socket

As reported by syzbot [1], there is a memory leak while closing the
socket. We partially solved this issue with commit ac03046
("vsock/virtio: free packets during the socket release"), but we
forgot to drain the RX queue when the socket is definitely closed by
the scheduled work.

To avoid future issues, let's use the new virtio_transport_remove_sock()
to drain the RX queue before removing the socket from the af_vsock lists
calling vsock_remove_sock().

[1] https://syzkaller.appspot.com/bug?extid=24452624fc4c571eedd9

Fixes: ac03046 ("vsock/virtio: free packets during the socket release")
Reported-and-tested-by: syzbot+24452624fc4c571eedd9@syzkaller.appspotmail.com
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: stefano-garzarella

net/vmw_vsock/virtio_transport_common.c

@@ -733,6 +733,23 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
 	return t->send_pkt(reply);
 }
 
+/* This function should be called with sk_lock held and SOCK_DONE set */
+static void virtio_transport_remove_sock(struct vsock_sock *vsk)
+{
+	struct virtio_vsock_sock *vvs = vsk->trans;
+	struct virtio_vsock_pkt *pkt, *tmp;
+
+	/* We don't need to take rx_lock, as the socket is closing and we are
+	 * removing it.
+	 */
+	list_for_each_entry_safe(pkt, tmp, &vvs->rx_queue, list) {
+		list_del(&pkt->list);
+		virtio_transport_free_pkt(pkt);
+	}
+
+	vsock_remove_sock(vsk);
+}
+
 static void virtio_transport_wait_close(struct sock *sk, long timeout)
 {
 	if (timeout) {
@@ -765,7 +782,7 @@ static void virtio_transport_do_close(struct vsock_sock *vsk,
 	    (!cancel_timeout || cancel_delayed_work(&vsk->close_work))) {
 		vsk->close_work_scheduled = false;
 
-		vsock_remove_sock(vsk);
+		virtio_transport_remove_sock(vsk);
 
 		/* Release refcnt obtained when we scheduled the timeout */
 		sock_put(sk);
@@ -828,22 +845,15 @@ static bool virtio_transport_close(struct vsock_sock *vsk)
 
 void virtio_transport_release(struct vsock_sock *vsk)
 {
-	struct virtio_vsock_sock *vvs = vsk->trans;
-	struct virtio_vsock_pkt *pkt, *tmp;
 	struct sock *sk = &vsk->sk;
 	bool remove_sock = true;
 
 	if (sk->sk_type == SOCK_STREAM)
 		remove_sock = virtio_transport_close(vsk);
 
-	list_for_each_entry_safe(pkt, tmp, &vvs->rx_queue, list) {
-		list_del(&pkt->list);
-		virtio_transport_free_pkt(pkt);
-	}
-
 	if (remove_sock) {
 		sock_set_flag(sk, SOCK_DONE);
-		vsock_remove_sock(vsk);
+		virtio_transport_remove_sock(vsk);
 	}
 }
 EXPORT_SYMBOL_GPL(virtio_transport_release);