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@xxxxxxxxxxxxxxx> > Reported-by: syzbot+adc3cb32385586bec859@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx> > --- > 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
