From: Lee Jones <lee.jones@linaro.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: mst@redhat.com, jasowang@redhat.com,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, stable@vger.kernel.org,
syzbot+adc3cb32385586bec859@syzkaller.appspotmail.com
Subject: Re: [PATCH 1/1] vhost: Protect the virtqueue from being cleared whilst still in use
Date: Tue, 8 Mar 2022 08:10:06 +0000 [thread overview]
Message-ID: <YicPXnNFHpoJHcUN@google.com> (raw)
In-Reply-To: <YiZeB7l49KC2Y5Gz@kroah.com>
On Mon, 07 Mar 2022, Greg KH wrote:
> 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?
No, Syzbot doesn't report warnings, only BUGs and memory corruption.
> And what happens if the mutex is locked _RIGHT_ after you checked it?
> You still have a race...
No, we miss a warning that one time. Memory is still protected.
--
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog
next prev parent reply other threads:[~2022-03-08 8:10 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-07 19:17 [PATCH 1/1] vhost: Protect the virtqueue from being cleared whilst still in use Lee Jones
2022-03-07 19:33 ` Greg KH
2022-03-07 22:39 ` Michael S. Tsirkin
2022-03-08 8:10 ` Lee Jones [this message]
2022-03-08 8:11 ` Lee Jones
2022-03-08 8:57 ` Greg KH
2022-03-08 9:15 ` Lee Jones
2022-03-08 9:57 ` Greg KH
2022-03-08 10:08 ` Lee Jones
2022-03-08 10:55 ` Michael S. Tsirkin
2022-03-08 11:45 ` Greg KH
2022-03-08 12:27 ` Michael S. Tsirkin
2022-03-08 13:17 ` Lee Jones
2022-03-08 17:17 ` Michael S. Tsirkin
2022-03-08 11:05 ` Michael S. Tsirkin
2022-03-09 18:52 ` Leon Romanovsky
2022-03-07 22:37 ` Michael S. Tsirkin
2022-03-08 8:01 ` Lee Jones
2022-03-08 11:07 ` Michael S. Tsirkin
2022-03-08 6:15 ` Jason Wang
2022-03-08 8:08 ` Lee Jones
2022-03-08 11:06 ` Michael S. Tsirkin
-- strict thread matches above, loose matches on Subject: below --
2022-03-14 8:43 Lee Jones
2022-03-14 8:56 ` Greg KH
2022-03-14 11:49 ` Michael S. Tsirkin
2022-03-14 12:47 ` Lee Jones
2022-03-02 7:54 Lee Jones
2022-03-02 9:34 ` Stefano Garzarella
2022-03-02 10:07 ` Lee Jones
2022-03-02 13:35 ` Michael S. Tsirkin
2022-03-02 14:11 ` Stefano Garzarella
2022-03-02 14:50 ` Michael S. Tsirkin
2022-03-02 15:36 ` Stefano Garzarella
2022-03-04 16:46 ` Michael S. Tsirkin
2022-03-02 13:30 ` Michael S. Tsirkin
2022-03-02 13:56 ` Lee Jones
2022-03-02 14:51 ` Michael S. Tsirkin
2022-03-02 14:57 ` Lee Jones
2022-03-02 16:28 ` Stefano Garzarella
2022-03-02 16:30 ` Michael S. Tsirkin
2022-03-02 16:49 ` Lee Jones
2022-03-02 17:10 ` Stefano Garzarella
2022-03-03 14:17 ` Lee Jones
2022-03-04 5:00 ` Michael S. Tsirkin
2022-03-04 15:22 ` Lee Jones
2022-03-04 16:48 ` Michael S. Tsirkin
2022-03-04 16:56 ` Lee Jones
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