[PATCH net] vhost: synchronize IOTLB message with dev cleanup

[Jason Wang]

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 <threeear...@gmail.com>
Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API")
Signed-off-by: Jason Wang <jasow...@redhat.com>
---
 drivers/vhost/vhost.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index f3bd8e9..f0be5f3 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -981,6 +981,7 @@ 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:
@@ -1016,6 +1017,8 @@ 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,
-- 
2.7.4