Re: [PATCH v2 1/2] vhost: fix vhost_vq_access_ok() log check
On Tue, Apr 10, 2018 at 04:22:35PM +0300, Michael S. Tsirkin wrote:
> On Tue, Apr 10, 2018 at 01:26:29PM +0800, Stefan Hajnoczi wrote:
> > Commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ("vhost: validate log
> > when IOTLB is enabled") introduced a regression. The logic was
> > originally:
> >
> > if (vq->iotlb)
> > return 1;
> > return A && B;
> >
> > After the patch the short-circuit logic for A was inverted:
> >
> > if (A || vq->iotlb)
> > return A;
> > return B;
> >
> > This patch fixes the regression by rewriting the checks in the obvious
> > way, no longer returning A when vq->iotlb is non-NULL (which is hard to
> > understand).
> >
> > Reported-by: syzbot+65a84dde0214b0387...@syzkaller.appspotmail.com
> > Cc: Jason Wang
> > Signed-off-by: Stefan Hajnoczi
>
> This patch only makes sense after patch 2/2 is applied.
> Otherwise the logic seems reversed below.
>
> Can you pls squash these two?
Oh, in fact the patch is ok. This just goes to show
that patch 2/2 is useful. But squashing is not required.
Sorry about the noise.
Acked-by: Michael S. Tsirkin
Fixes: d65026c6c ("vhost: validate log when IOTLB is enabled")
probably stable material since patch it fixes was queued to stable?
> > ---
> > drivers/vhost/vhost.c | 8 +---
> > 1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index 5320039671b7..93fd0c75b0d8 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -1244,10 +1244,12 @@ static int vq_log_access_ok(struct vhost_virtqueue
> > *vq,
> > /* Caller should have vq mutex and device mutex */
> > int vhost_vq_access_ok(struct vhost_virtqueue *vq)
> > {
> > - int ret = vq_log_access_ok(vq, vq->log_base);
> > + if (!vq_log_access_ok(vq, vq->log_base))
> > + return 0;
> >
> > - if (ret || vq->iotlb)
> > - return ret;
> > + /* Access validation occurs at prefetch time with IOTLB */
> > + if (vq->iotlb)
> > + return 1;
> >
> > return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
> > }
> > --
> > 2.14.3
Re: [PATCH v2 1/2] vhost: fix vhost_vq_access_ok() log check
On Tue, Apr 10, 2018 at 01:26:29PM +0800, Stefan Hajnoczi wrote:
> Commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ("vhost: validate log
> when IOTLB is enabled") introduced a regression. The logic was
> originally:
>
> if (vq->iotlb)
> return 1;
> return A && B;
>
> After the patch the short-circuit logic for A was inverted:
>
> if (A || vq->iotlb)
> return A;
> return B;
>
> This patch fixes the regression by rewriting the checks in the obvious
> way, no longer returning A when vq->iotlb is non-NULL (which is hard to
> understand).
>
> Reported-by: syzbot+65a84dde0214b0387...@syzkaller.appspotmail.com
> Cc: Jason Wang
> Signed-off-by: Stefan Hajnoczi
This patch only makes sense after patch 2/2 is applied.
Otherwise the logic seems reversed below.
Can you pls squash these two?
> ---
> drivers/vhost/vhost.c | 8 +---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 5320039671b7..93fd0c75b0d8 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -1244,10 +1244,12 @@ static int vq_log_access_ok(struct vhost_virtqueue
> *vq,
> /* Caller should have vq mutex and device mutex */
> int vhost_vq_access_ok(struct vhost_virtqueue *vq)
> {
> - int ret = vq_log_access_ok(vq, vq->log_base);
> + if (!vq_log_access_ok(vq, vq->log_base))
> + return 0;
>
> - if (ret || vq->iotlb)
> - return ret;
> + /* Access validation occurs at prefetch time with IOTLB */
> + if (vq->iotlb)
> + return 1;
>
> return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
> }
> --
> 2.14.3
[PATCH v2 1/2] vhost: fix vhost_vq_access_ok() log check
Commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ("vhost: validate log
when IOTLB is enabled") introduced a regression. The logic was
originally:
if (vq->iotlb)
return 1;
return A && B;
After the patch the short-circuit logic for A was inverted:
if (A || vq->iotlb)
return A;
return B;
This patch fixes the regression by rewriting the checks in the obvious
way, no longer returning A when vq->iotlb is non-NULL (which is hard to
understand).
Reported-by: syzbot+65a84dde0214b0387...@syzkaller.appspotmail.com
Cc: Jason Wang
Signed-off-by: Stefan Hajnoczi
---
drivers/vhost/vhost.c | 8 +---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 5320039671b7..93fd0c75b0d8 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1244,10 +1244,12 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq,
/* Caller should have vq mutex and device mutex */
int vhost_vq_access_ok(struct vhost_virtqueue *vq)
{
- int ret = vq_log_access_ok(vq, vq->log_base);
+ if (!vq_log_access_ok(vq, vq->log_base))
+ return 0;
- if (ret || vq->iotlb)
- return ret;
+ /* Access validation occurs at prefetch time with IOTLB */
+ if (vq->iotlb)
+ return 1;
return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
}
--
2.14.3
