virtio_balloon: prevent pfn array overflow

[ 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>

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index c962d9b370c697170c0cc39956676ee1df8a0a7e..d2c4eb9efd70b56dfd4178ccfd6a67d476864622 100644 (file)
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -157,6 +157,8 @@ 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.