Commit f68b992b authored Dec 28, 2015 by Minchan Kim Committed by Michael S. Tsirkin Jan 12, 2016

virtio_balloon: fix race by fill and leak



During my compaction-related stuff, I encountered a bug
with ballooning.

With repeated inflating and deflating cycle, guest memory(
ie, cat /proc/meminfo | grep MemTotal) is decreased and
couldn't be recovered.

The reason is balloon_lock doesn't cover release_pages_balloon
so struct virtio_balloon fields could be overwritten by race
of fill_balloon(e,g, vb->*pfns could be critical).

This patch fixes it in my test.

Cc: <stable@vger.kernel.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

parent 779a6a36

drivers/virtio/virtio_balloon.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -209,8 +209,8 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
		*/
		if (vb->num_pfns != 0)
		tell_host(vb, vb->deflate_vq);
		mutex_unlock(&vb->balloon_lock);
		release_pages_balloon(vb);
		mutex_unlock(&vb->balloon_lock);
		return num_freed_pages;
		}