On Tue, May 22, 2018 at 07:58:57PM +0800, Jason Wang wrote:
> 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@xxxxxxxxx>
> Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API")
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
We should think of a way to have a per-vq lock here, but for now:
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> 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
