vhost_net: add missing lock nesting notation

BugLink: http://bugs.launchpad.net/bugs/1763366
[ Upstream commit aaa3149bbee9ba9b4e6f0bd6e3e7d191edeae942 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 5636c7ca8ebac2aa92c0c43d3187f01d920d786e..0020ae906bf9c93f442241bbd28d4929ca7a2c72 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -618,7 +618,7 @@ 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();
@@ -751,7 +751,7 @@ 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;