On Wed, Mar 02, 2022 at 08:35:08AM -0500, Michael S. Tsirkin wrote:
On Wed, Mar 02, 2022 at 10:34:46AM +0100, Stefano Garzarella wrote:
On Wed, Mar 02, 2022 at 07:54:21AM +0000, Lee Jones wrote:
> vhost_vsock_handle_tx_kick() already holds the mutex during its call
> to vhost_get_vq_desc(). All we have to do is take the same lock
> during virtqueue clean-up and we mitigate the reported issues.
>
> Link: https://syzkaller.appspot.com/bug?extid=279432d30d825e63ba00
This issue is similar to [1] that should be already fixed upstream by [2].
However I think this patch would have prevented some issues, because
vhost_vq_reset() sets vq->private to NULL, preventing the worker from
running.
Anyway I think that when we enter in vhost_dev_cleanup() the worker should
be already stopped, so it shouldn't be necessary to take the mutex. But in
order to prevent future issues maybe it's better to take them, so:
Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
[1]
https://syzkaller.appspot.com/bug?id=993d8b5e64393ed9e6a70f9ae4de0119c605a822
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58da53ffd70294ebea8ecd0eb45fd0d74add9f9
Right. I want to queue this but I would like to get a warning
so we can detect issues like [2] before they cause more issues.
I agree, what about moving the warning that we already have higher up,
right at the beginning of the function?
I mean something like this:
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 59edb5a1ffe2..1721ff3f18c0 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -692,6 +692,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
{
int i;
+ WARN_ON(!llist_empty(&dev->work_list));
+
for (i = 0; i < dev->nvqs; ++i) {
if (dev->vqs[i]->error_ctx)
eventfd_ctx_put(dev->vqs[i]->error_ctx);
@@ -712,7 +714,6 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
dev->iotlb = NULL;
vhost_clear_msg(dev);
wake_up_interruptible_poll(&dev->wait, EPOLLIN | EPOLLRDNORM);
- WARN_ON(!llist_empty(&dev->work_list));
if (dev->worker) {
kthread_stop(dev->worker);
dev->worker = NULL;
And maybe we can also check vq->private and warn in the loop, because
the work_list may be empty if the device is doing nothing.
Thanks,
Stefano
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