[PATCH 4.14 164/237] virtio_balloon: prevent pfn array overflow

Greg Kroah-Hartman
2020-02-27T13:59:19Z

From: Michael S. Tsirkin <mst@redhat.com>

[ Upstream commit 6e9826e77249355c09db6ba41cd3f84e89f4b614 ]

Make sure, at build time, that pfn array is big enough to hold a single
page. It happens to be true since the PAGE_SHIFT value at the moment is
20, which is 1M - exactly 256 4K balloon pages.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/virtio/virtio_balloon.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 499531608fa26..71970773aad13 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -132,6 +132,8 @@ static void set_page_pfns(struct virtio_balloon *vb,
{
unsigned int i;

+ BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
+
/*
* Set balloon pfns pointing at this page.
* Note that the first pfn points at start of the page.
--
2.20.1