Patch "vhost: use mutex_lock_nested() in vhost_dev_lock_vqs()" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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;a=summary

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