On Wed, Mar 02, 2022 at 05:28:31PM +0100, Stefano Garzarella wrote:
On Wed, Mar 2, 2022 at 3:57 PM Lee Jones lee.jones@linaro.org wrote:
On Wed, 02 Mar 2022, Michael S. Tsirkin wrote:
On Wed, Mar 02, 2022 at 01:56:35PM +0000, Lee Jones wrote:
On Wed, 02 Mar 2022, Michael S. Tsirkin 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
Cc: stable@vger.kernel.org Reported-by: syzbot+adc3cb32385586bec859@syzkaller.appspotmail.com Signed-off-by: Lee Jones lee.jones@linaro.org
drivers/vhost/vhost.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 59edb5a1ffe28..bbaff6a5e21b8 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -693,6 +693,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev) int i;
for (i = 0; i < dev->nvqs; ++i) {
mutex_lock(&dev->vqs[i]->mutex); if (dev->vqs[i]->error_ctx) eventfd_ctx_put(dev->vqs[i]->error_ctx); if (dev->vqs[i]->kick)@@ -700,6 +701,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev) if (dev->vqs[i]->call_ctx.ctx) eventfd_ctx_put(dev->vqs[i]->call_ctx.ctx); vhost_vq_reset(dev, dev->vqs[i]);
mutex_unlock(&dev->vqs[i]->mutex); }So this is a mitigation plan but the bug is still there though we don't know exactly what it is. I would prefer adding something like WARN_ON(mutex_is_locked(vqs[i]->mutex) here - does this make sense?
As a rework to this, or as a subsequent patch?
Can be a separate patch.
Just before the first lock I assume?
I guess so, yes.
No problem. Patch to follow.
I'm also going to attempt to debug the root cause, but I'm new to this subsystem to it might take a while for me to get my head around.
IIUC the root cause should be the same as the one we solved here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
The worker was not stopped before calling vhost_dev_cleanup(). So while the worker was still running we were going to free memory or initialize fields while it was still using virtqueue.
Cheers, Stefano
Right, and I agree but it's not the root though, we do attempt to stop all workers.