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

vhost: use mutex_lock_nested() in vhost_dev_lock_vqs()

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: vhost-use-mutex_lock_nested-in-vhost_dev_lock_vqs.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 e9cb4239134c860e5f92c75bf5321bd377bb505b Mon Sep 17 00:00:00 2001

From: Jason Wang jasowang@redhat.com Date: Tue, 23 Jan 2018 17:27:25 +0800 Subject: vhost: use mutex_lock_nested() in vhost_dev_lock_vqs()

From: Jason Wang jasowang@redhat.com

commit e9cb4239134c860e5f92c75bf5321bd377bb505b upstream.

We used to call mutex_lock() in vhost_dev_lock_vqs() which tries to hold mutexes of all virtqueues. This may confuse lockdep to report a possible deadlock because of trying to hold locks belong to same class. Switch to use mutex_lock_nested() to avoid false positive.

Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API") Reported-by: syzbot+dbb7c1161485e61b0241@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/vhost.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -849,7 +849,7 @@ static void vhost_dev_lock_vqs(struct vh { int i = 0; for (i = 0; i < d->nvqs; ++i) - mutex_lock(&d->vqs[i]->mutex); + mutex_lock_nested(&d->vqs[i]->mutex, i); }

static void vhost_dev_unlock_vqs(struct vhost_dev *d)

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

queue-4.9/vhost-use-mutex_lock_nested-in-vhost_dev_lock_vqs.patch queue-4.9/ptr_ring-fail-early-if-queue-occupies-more-than-kmalloc_max_size.patch