Patch "vhost_net: add missing lock nesting notation" has been added to the 4.9-stable tree

Patch "vhost_net: add missing lock nesting notation" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    vhost_net: add missing lock nesting notation

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     vhost_net-add-missing-lock-nesting-notation.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Apr 11 10:26:56 CEST 2018
From: Jason Wang <jasowang@redhat.com>
Date: Mon, 26 Mar 2018 16:10:23 +0800
Subject: vhost_net: add missing lock nesting notation

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
@@ -524,7 +524,7 @@ 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();
@@ -657,7 +657,7 @@ 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;


Patches currently in stable-queue which might be from jasowang@redhat.com are

queue-4.9/skbuff-return-emsgsize-in-skb_to_sgvec-to-prevent-overflow.patch
queue-4.9/virtio_net-check-return-value-of-skb_to_sgvec-always.patch
queue-4.9/vhost-validate-log-when-iotlb-is-enabled.patch
queue-4.9/vhost_net-add-missing-lock-nesting-notation.patch
queue-4.9/vhost-correctly-remove-wait-queue-during-poll-failure.patch
queue-4.9/virtio_net-check-return-value-of-skb_to_sgvec-in-one-more-location.patch