From be1fc38a6f84a2b3b5d648ced2ce5d9b36851868 Mon Sep 17 00:00:00 2001 From: Konstantin Neumoin Date: Mon, 11 Jul 2016 15:28:59 +0300 Subject: [PATCH] balloon: check the number of available pages in leak balloon 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 Signed-off-by: Denis V. Lunev CC: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- drivers/virtio/virtio_balloon.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 28153fb2225d..2975c5089dac 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -142,6 +142,8 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num) /* We can only do one array worth at a time. */ num = min(num, ARRAY_SIZE(vb->pfns)); + /* 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++) { page = list_first_entry(&vb->pages, struct page, lru); list_del(&page->lru); -- 2.39.2