Patch "balloon: check the number of available pages in leak balloon" has been added to the 4.7-stable tree

Patch "balloon: check the number of available pages in leak balloon" has been added to the 4.7-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    balloon: check the number of available pages in leak balloon

to the 4.7-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     balloon-check-the-number-of-available-pages-in-leak-balloon.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 37cf99e08c6fb4dcea0f9ad2b13b6daa8c76a711 Mon Sep 17 00:00:00 2001
From: Konstantin Neumoin <kneumoin@virtuozzo.com>
Date: Mon, 11 Jul 2016 15:28:59 +0300
Subject: balloon: check the number of available pages in leak balloon

From: Konstantin Neumoin <kneumoin@virtuozzo.com>

commit 37cf99e08c6fb4dcea0f9ad2b13b6daa8c76a711 upstream.

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.

Signed-off-by: Konstantin Neumoin <kneumoin@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/virtio/virtio_balloon.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -202,6 +202,8 @@ static unsigned leak_balloon(struct virt
 	num = min(num, ARRAY_SIZE(vb->pfns));
 
 	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;
 	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 		page = balloon_page_dequeue(vb_dev_info);


Patches currently in stable-queue which might be from kneumoin@virtuozzo.com are

queue-4.7/balloon-check-the-number-of-available-pages-in-leak-balloon.patch