On Mon, Sep 07, 2020 at 06:52:19PM +0800, Zhu Lingshan wrote:
> In vhost_vdpa ioctl SET_BACKEND_FEATURES path, currect code
> would try to acquire vhost dev mutex twice
> (first shown in vhost_vdpa_unlocked_ioctl), which can lead
> to a dead lock issue.
> This commit removed mutex operations in vhost_set_backend_features.
> As a compensation for vhost_net, a followinig commit will add
> needed mutex lock/unlock operations in a new function
> vhost_net_set_backend_features() which is a wrap of
> vhost_set_backend_features().
>
> Signed-off-by: Zhu Lingshan <lingshan.zhu@xxxxxxxxx>
I think you need to squash these two or reorder, we can't first
make code racy then fix it up.
> ---
> drivers/vhost/vhost.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index b45519ca66a7..e03c9e6f058f 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -2591,14 +2591,12 @@ void vhost_set_backend_features(struct vhost_dev *dev, u64 features)
> struct vhost_virtqueue *vq;
> int i;
>
> - mutex_lock(&dev->mutex);
> for (i = 0; i < dev->nvqs; ++i) {
> vq = dev->vqs[i];
> mutex_lock(&vq->mutex);
> vq->acked_backend_features = features;
> mutex_unlock(&vq->mutex);
> }
> - mutex_unlock(&dev->mutex);
> }
> EXPORT_SYMBOL_GPL(vhost_set_backend_features);
>
> --
> 2.18.4
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