On Mon, Mar 07, 2022 at 07:17:57PM +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 here is take the same lock during virtqueue clean-up and we mitigate the reported issues.
Also WARN() as a precautionary measure. The purpose of this is to capture possible future race conditions which may pop up over time.
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 | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 59edb5a1ffe28..ef7e371e3e649 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -693,6 +693,15 @@ void vhost_dev_cleanup(struct vhost_dev *dev) int i; for (i = 0; i < dev->nvqs; ++i) {
/* No workers should run here by design. However, races have* previously occurred where drivers have been unable to flush* all work properly prior to clean-up. Without a successful* flush the guest will malfunction, but avoiding host memory* corruption in those cases does seem preferable.*/WARN_ON(mutex_is_locked(&dev->vqs[i]->mutex));
So you are trading one syzbot triggered issue for another one in the future? :)
If this ever can happen, handle it, but don't log it with a WARN_ON() as that will trigger the panic-on-warn boxes, as well as syzbot. Unless you want that to happen?
And what happens if the mutex is locked _RIGHT_ after you checked it? You still have a race...
thanks,
greg k-h