linux-kernel - [PATCH 02/12] mm,migration: Do not try to migrate unmapped anonymous pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1266516162-14154-3-git-send-email-mel@csn.ul.ie>
Date:	Thu, 18 Feb 2010 18:02:32 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 02/12] mm,migration: Do not try to migrate unmapped anonymous pages

rmap_walk_anon() was triggering errors in memory compaction that looks like
use-after-free errors in anon_vma. The problem appears to be that between
the page being isolated from the LRU and rcu_read_lock() being taken, the
mapcount of the page dropped to 0 and the anon_vma was freed. This patch
skips the migration of anon pages that are not mapped by anyone.

Signed-off-by: Mel Gorman <mel@....ul.ie>
---
 mm/migrate.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 63addfa..1ce6a2f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -606,6 +606,16 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
 	 * just care Anon page here.
 	 */
 	if (PageAnon(page)) {
+		/*
+		 * If the page has no mappings any more, just bail. An
+		 * unmapped anon page is likely to be freed soon but worse,
+		 * it's possible its anon_vma disappeared between when
+		 * the page was isolated and when we reached here while
+		 * the RCU lock was not held
+		 */
+		if (!page_mapcount(page))
+			goto uncharge;
+
 		rcu_read_lock();
 		rcu_locked = 1;
 		anon_vma = page_anon_vma(page);
-- 
1.6.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/