* [PATCH v2] virtio_balloon: leak_balloon(): only tell host if we got pages deflated
@ 2013-06-06 1:18 Luiz Capitulino
2013-06-06 14:13 ` Rafael Aquini
2013-06-17 17:17 ` Luiz Capitulino
0 siblings, 2 replies; 4+ messages in thread
From: Luiz Capitulino @ 2013-06-06 1:18 UTC (permalink / raw)
To: linux-mm; +Cc: linux-kernel, kvm, aquini
The balloon_page_dequeue() function can return NULL. If it does for
the first page being freed, then leak_balloon() will create a
scatter list with len=0. Which in turn seems to generate an invalid
virtio request.
I didn't get this in practice, I found it by code review. On the other
hand, such an invalid virtio request will cause errors in QEMU and
fill_balloon() also performs the same check implemented by this commit.
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
---
o v2
- Improve changelog
drivers/virtio/virtio_balloon.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index bd3ae32..71af7b5 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -191,7 +191,8 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
* virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
* is true, we *have* to do it in this order
*/
- tell_host(vb, vb->deflate_vq);
+ if (vb->num_pfns != 0)
+ tell_host(vb, vb->deflate_vq);
mutex_unlock(&vb->balloon_lock);
release_pages_by_pfn(vb->pfns, vb->num_pfns);
}
--
1.8.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] virtio_balloon: leak_balloon(): only tell host if we got pages deflated
2013-06-06 1:18 [PATCH v2] virtio_balloon: leak_balloon(): only tell host if we got pages deflated Luiz Capitulino
@ 2013-06-06 14:13 ` Rafael Aquini
2013-06-06 14:19 ` Luiz Capitulino
2013-06-17 17:17 ` Luiz Capitulino
1 sibling, 1 reply; 4+ messages in thread
From: Rafael Aquini @ 2013-06-06 14:13 UTC (permalink / raw)
To: Luiz Capitulino; +Cc: linux-mm, linux-kernel, kvm
On Wed, Jun 05, 2013 at 09:18:37PM -0400, Luiz Capitulino wrote:
> The balloon_page_dequeue() function can return NULL. If it does for
> the first page being freed, then leak_balloon() will create a
> scatter list with len=0. Which in turn seems to generate an invalid
> virtio request.
>
> I didn't get this in practice, I found it by code review. On the other
> hand, such an invalid virtio request will cause errors in QEMU and
> fill_balloon() also performs the same check implemented by this commit.
>
> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> Acked-by: Rafael Aquini <aquini@redhat.com>
> ---
>
> o v2
>
> - Improve changelog
>
> drivers/virtio/virtio_balloon.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index bd3ae32..71af7b5 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -191,7 +191,8 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
> * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
> * is true, we *have* to do it in this order
> */
> - tell_host(vb, vb->deflate_vq);
Luiz, sorry for not being clearer before. I was referring to add a commentary on
code, to explain in short words why we should not get rid of this check point.
> + if (vb->num_pfns != 0)
> + tell_host(vb, vb->deflate_vq);
> mutex_unlock(&vb->balloon_lock);
If the comment is regarded as unnecessary, then just ignore my suggestion. I'm
OK with your patch. :)
Cheers!
-- Rafael
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] virtio_balloon: leak_balloon(): only tell host if we got pages deflated
2013-06-06 14:13 ` Rafael Aquini
@ 2013-06-06 14:19 ` Luiz Capitulino
0 siblings, 0 replies; 4+ messages in thread
From: Luiz Capitulino @ 2013-06-06 14:19 UTC (permalink / raw)
To: Rafael Aquini; +Cc: linux-mm, linux-kernel, kvm
On Thu, 6 Jun 2013 11:13:58 -0300
Rafael Aquini <aquini@redhat.com> wrote:
> On Wed, Jun 05, 2013 at 09:18:37PM -0400, Luiz Capitulino wrote:
> > The balloon_page_dequeue() function can return NULL. If it does for
> > the first page being freed, then leak_balloon() will create a
> > scatter list with len=0. Which in turn seems to generate an invalid
> > virtio request.
> >
> > I didn't get this in practice, I found it by code review. On the other
> > hand, such an invalid virtio request will cause errors in QEMU and
> > fill_balloon() also performs the same check implemented by this commit.
> >
> > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> > Acked-by: Rafael Aquini <aquini@redhat.com>
> > ---
> >
> > o v2
> >
> > - Improve changelog
> >
> > drivers/virtio/virtio_balloon.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> > index bd3ae32..71af7b5 100644
> > --- a/drivers/virtio/virtio_balloon.c
> > +++ b/drivers/virtio/virtio_balloon.c
> > @@ -191,7 +191,8 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
> > * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
> > * is true, we *have* to do it in this order
> > */
> > - tell_host(vb, vb->deflate_vq);
>
> Luiz, sorry for not being clearer before. I was referring to add a commentary on
> code, to explain in short words why we should not get rid of this check point.
Oh.
> > + if (vb->num_pfns != 0)
> > + tell_host(vb, vb->deflate_vq);
> > mutex_unlock(&vb->balloon_lock);
>
> If the comment is regarded as unnecessary, then just ignore my suggestion. I'm
> OK with your patch. :)
IMHO, the code is clear enough.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] virtio_balloon: leak_balloon(): only tell host if we got pages deflated
2013-06-06 1:18 [PATCH v2] virtio_balloon: leak_balloon(): only tell host if we got pages deflated Luiz Capitulino
2013-06-06 14:13 ` Rafael Aquini
@ 2013-06-17 17:17 ` Luiz Capitulino
1 sibling, 0 replies; 4+ messages in thread
From: Luiz Capitulino @ 2013-06-17 17:17 UTC (permalink / raw)
To: akpm; +Cc: linux-mm, linux-kernel, kvm, aquini
On Wed, 5 Jun 2013 21:18:37 -0400
Luiz Capitulino <lcapitulino@redhat.com> wrote:
> The balloon_page_dequeue() function can return NULL. If it does for
> the first page being freed, then leak_balloon() will create a
> scatter list with len=0. Which in turn seems to generate an invalid
> virtio request.
>
> I didn't get this in practice, I found it by code review. On the other
> hand, such an invalid virtio request will cause errors in QEMU and
> fill_balloon() also performs the same check implemented by this commit.
>
> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> Acked-by: Rafael Aquini <aquini@redhat.com>
Andrew, can you pick this one?
> ---
>
> o v2
>
> - Improve changelog
>
> drivers/virtio/virtio_balloon.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index bd3ae32..71af7b5 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -191,7 +191,8 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
> * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
> * is true, we *have* to do it in this order
> */
> - tell_host(vb, vb->deflate_vq);
> + if (vb->num_pfns != 0)
> + tell_host(vb, vb->deflate_vq);
> mutex_unlock(&vb->balloon_lock);
> release_pages_by_pfn(vb->pfns, vb->num_pfns);
> }
^ permalink raw reply [flat|nested] 4+ messages in thread
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2013-06-06 1:18 [PATCH v2] virtio_balloon: leak_balloon(): only tell host if we got pages deflated Luiz Capitulino
2013-06-06 14:13 ` Rafael Aquini
2013-06-06 14:19 ` Luiz Capitulino
2013-06-17 17:17 ` Luiz Capitulino
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