From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754877Ab1GFSpO (ORCPT ); Wed, 6 Jul 2011 14:45:14 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:33338 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996Ab1GFSpM (ORCPT ); Wed, 6 Jul 2011 14:45:12 -0400 From: "Rafael J. Wysocki" To: Linux PM mailing list Subject: [PATCH] PM / Hibernate: Fix free_unnecessary_pages() Date: Wed, 6 Jul 2011 20:46:23 +0200 User-Agent: KMail/1.13.6 (Linux/3.0.0-rc5+; KDE/4.6.0; x86_64; ; ) Cc: LKML , Matthew Garrett MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201107062046.23967.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rafael J. Wysocki There is a bug in free_unnecessary_pages() that causes it to attempt to free too many pages in some cases, which triggers the BUG_ON() in memory_bm_clear_bit() for copy_bm. Namely, if count_data_pages() is initially greater than alloc_normal, we get to_free_normal equal to 0 and "save" greater from 0. In that case, if the sum of "save" and count_highmem_pages() is greater than alloc_highmem, we subtract a positive number from to_free_normal. Hence, since to_free_normal was 0 before the subtraction and is an unsigned int, the result is converted to a huge positive number that is used as the number of pages to free. Fix this bug by checking if to_free_normal is actually greater than or equal to the number we're going to subtract from it. Signed-off-by: Rafael J. Wysocki Reported-and-tested-by: Matthew Garrett Cc: stable@kernel.org --- kernel/power/snapshot.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) Index: linux-2.6/kernel/power/snapshot.c =================================================================== --- linux-2.6.orig/kernel/power/snapshot.c +++ linux-2.6/kernel/power/snapshot.c @@ -1211,7 +1211,11 @@ static void free_unnecessary_pages(void) to_free_highmem = alloc_highmem - save; } else { to_free_highmem = 0; - to_free_normal -= save - alloc_highmem; + save -= alloc_highmem; + if (to_free_normal > save) + to_free_normal -= save; + else + to_free_normal = 0; } memory_bm_position_reset(©_bm);