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SubjectRe: [PATCH net] vhost_net: add missing lock nesting notation
On Mon, Mar 26, 2018 at 04:10:23PM +0800, Jason Wang wrote:
> 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>

> ---
> drivers/vhost/net.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 8139bc7..12bcfba 100644
> --- 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;
> --
> 2.7.4

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