vhost_net: add missing lock nesting notation

We try to hold TX virtqueue mutex in vhost_net_rx_peek_head_len()
after RX virtqueue mutex is held in handle_rx(). This requires an
appropriate lock nesting notation to calm down deadlock detector.

Fixes: 0308813724606 ("vhost_net: basic polling support")
Reported-by: syzbot+7f073540b1384a614e09@syzkaller.appspotmail.com
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 8139bc70ad7dcf09b2d2311fc1eab9d450ab4814..12bcfbac2cc9de526e1bfdcaf558c9b3396976a3 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -630,7 +630,7 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
 
        if (!len && vq->busyloop_timeout) {
                /* Both tx vq and rx socket were polled here */
-               mutex_lock(&vq->mutex);
+               mutex_lock_nested(&vq->mutex, 1);
                vhost_disable_notify(&net->dev, vq);
 
                preempt_disable();
@@ -763,7 +763,7 @@ static void handle_rx(struct vhost_net *net)
        struct iov_iter fixup;
        __virtio16 num_buffers;
 
-       mutex_lock(&vq->mutex);
+       mutex_lock_nested(&vq->mutex, 0);
        sock = vq->private_data;
        if (!sock)
                goto out;