3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Luiz Capitulino <lcapitul...@redhat.com>
commit 8c6bab4f3874d31804a00782c48a8f244a0d3cc0 upstream.
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.
This bug was introduced in e2250429.
Signed-off-by: Luiz Capitulino <lcapitul...@redhat.com>
Acked-by: Rafael Aquini <aqu...@redhat.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Rusty Russell <ru...@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/virtio/virtio_balloon.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/virtio/virtio_balloon.c
+++ b/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);
}
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