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    Subject[PATCH 4.14 137/138] vhost_net: add missing lock nesting notation
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jason Wang <jasowang@redhat.com>


    [ 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>
    ---
    drivers/vhost/net.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/drivers/vhost/net.c
    +++ b/drivers/vhost/net.c
    @@ -622,7 +622,7 @@ static int vhost_net_rx_peek_head_len(st

    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();
    @@ -755,7 +755,7 @@ static void handle_rx(struct vhost_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;

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