+ virtio_balloon-leak_balloon-only-tell-host-if-we-got-pages-deflated.patch added to -mm tree

+ virtio_balloon-leak_balloon-only-tell-host-if-we-got-pages-deflated.patch added to -mm tree

[akpm]

Subject: + virtio_balloon-leak_balloon-only-tell-host-if-we-got-pages-deflated.patch added to -mm tree
To: lcapitulino@redhat.com,aquini@redhat.com,rusty@rustcorp.com.au
From: akpm@linux-foundation.org
Date: Mon, 17 Jun 2013 15:27:02 -0700


The patch titled
     Subject: virtio_balloon: leak_balloon(): only tell host if we got pages deflated
has been added to the -mm tree.  Its filename is
     virtio_balloon-leak_balloon-only-tell-host-if-we-got-pages-deflated.patch

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------------------------------------------------------
From: Luiz Capitulino <lcapitulino@redhat.com>
Subject: virtio_balloon: leak_balloon(): only tell host if we got pages deflated

balloon_page_dequeue() 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>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/virtio/virtio_balloon.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff -puN drivers/virtio/virtio_balloon.c~virtio_balloon-leak_balloon-only-tell-host-if-we-got-pages-deflated drivers/virtio/virtio_balloon.c
--- a/drivers/virtio/virtio_balloon.c~virtio_balloon-leak_balloon-only-tell-host-if-we-got-pages-deflated
+++ a/drivers/virtio/virtio_balloon.c
@@ -191,7 +191,8 @@ static void leak_balloon(struct virtio_b
 	 * 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);
 }
_

Patches currently in -mm which might be from lcapitulino@redhat.com are

virtio_balloon-leak_balloon-only-tell-host-if-we-got-pages-deflated.patch