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Subject[PATCH net] vhost_net: add missing lock nesting notation
Date
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>
---
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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