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Subject[PATCH 1/2] virtio_balloon: fix race by fill and leak
Date
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>
---
drivers/virtio/virtio_balloon.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 7efc32945810..7d3e5d0e9aa4 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -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;
}

--
1.9.1


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