Commit 37cf99e0 authored by Konstantin Neumoin's avatar Konstantin Neumoin Committed by Michael S. Tsirkin

balloon: check the number of available pages in leak balloon

The balloon has a special mechanism that is subscribed to the oom
notification which leads to deflation for a fixed number of pages.
The number is always fixed even when the balloon is fully deflated.
But leak_balloon did not expect that the pages to deflate will be more
than taken, and raise a "BUG" in balloon_page_dequeue when page list
will be empty.

So, the simplest solution would be to check that the number of releases
pages is less or equal to the number taken pages.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarKonstantin Neumoin <kneumoin@virtuozzo.com>
Signed-off-by: default avatarDenis V. Lunev <den@openvz.org>
CC: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 04b96e55
...@@ -202,6 +202,8 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) ...@@ -202,6 +202,8 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
num = min(num, ARRAY_SIZE(vb->pfns)); num = min(num, ARRAY_SIZE(vb->pfns));
mutex_lock(&vb->balloon_lock); mutex_lock(&vb->balloon_lock);
/* We can't release more pages than taken */
num = min(num, (size_t)vb->num_pages);
for (vb->num_pfns = 0; vb->num_pfns < num; for (vb->num_pfns = 0; vb->num_pfns < num;
vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
page = balloon_page_dequeue(vb_dev_info); page = balloon_page_dequeue(vb_dev_info);
......
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