Commit 9f0f4835 authored by Minchan Kim's avatar Minchan Kim Committed by Luis Henriques

virtio_balloon: fix race by fill and leak

commit f68b992b upstream.

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.
Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 712df95d
......@@ -193,8 +193,8 @@ static void 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_by_pfn(vb->pfns, vb->num_pfns);
mutex_unlock(&vb->balloon_lock);
}
static inline void update_stat(struct virtio_balloon *vb, int idx,
......
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