vhost: synchronize IOTLB message with dev cleanup

BugLink: http://bugs.launchpad.net/bugs/1789666
[ Upstream commit 1b15ad683ab42a203f98b67045b40720e99d0e9a ]

DaeRyong Jeong reports a race between vhost_dev_cleanup() and
vhost_process_iotlb_msg():

Thread interleaving:
CPU0 (vhost_process_iotlb_msg)			CPU1 (vhost_dev_cleanup)
(In the case of both VHOST_IOTLB_UPDATE and
VHOST_IOTLB_INVALIDATE)

=====						=====
						vhost_umem_clean(dev->iotlb);
if (!dev->iotlb) {
	        ret = -EFAULT;
		        break;
}
						dev->iotlb = NULL;

The reason is we don't synchronize between them, fixing by protecting
vhost_process_iotlb_msg() with dev mutex.

Reported-by: DaeRyong Jeong <threeearcat@gmail.com>
Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API")
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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index a922d3d28a20ea1b3cdc5815cfbf8dcbb81f24a1..24df8d93a89b483d20f455a386299e5625b1b177 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -993,6 +993,7 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev,
 {
        int ret = 0;
 
+       mutex_lock(&dev->mutex);
        vhost_dev_lock_vqs(dev);
        switch (msg->type) {
        case VHOST_IOTLB_UPDATE:
@@ -1028,6 +1029,8 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev,
        }
 
        vhost_dev_unlock_vqs(dev);
+       mutex_unlock(&dev->mutex);
+
        return ret;
 }
 ssize_t vhost_chr_write_iter(struct vhost_dev *dev,