From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752259AbaKPWBx (ORCPT ); Sun, 16 Nov 2014 17:01:53 -0500 Received: from 1wt.eu ([62.212.114.60]:48004 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752226AbaKPWBu (ORCPT ); Sun, 16 Nov 2014 17:01:50 -0500 Message-Id: <20141116215329.060529649@1wt.eu> User-Agent: quilt/0.48-1 Date: Sun, 16 Nov 2014 22:53:38 +0100 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Vlastimil Babka , Bob Liu , Wanpeng Li , Michel Lespinasse , KOSAKI Motohiro , Rik van Riel , David Rientjes , Mel Gorman , Hugh Dickins , Joonsoo Kim , Andrew Morton , Linus Torvalds , Luis Henriques , Andy Whitcroft , Tim Gardner , Willy Tarreau Subject: [ 10/48] mm: try_to_unmap_cluster() should lock_page() before In-Reply-To: <28c765bc23bd4bae1611534e510f49f8@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ mlocking From: Vlastimil Babka commit 68f662b89de39aae5f43ecd3fbc6ea120d0a47cf upstream A BUG_ON(!PageLocked) was triggered in mlock_vma_page() by Sasha Levin fuzzing with trinity. The call site try_to_unmap_cluster() does not lock the pages other than its check_page parameter (which is already locked). The BUG_ON in mlock_vma_page() is not documented and its purpose is somewhat unclear, but apparently it serializes against page migration, which could otherwise fail to transfer the PG_mlocked flag. This would not be fatal, as the page would be eventually encountered again, but NR_MLOCK accounting would become distorted nevertheless. This patch adds a comment to the BUG_ON in mlock_vma_page() and munlock_vma_page() to that effect. The call site try_to_unmap_cluster() is fixed so that for page != check_page, trylock_page() is attempted (to avoid possible deadlocks as we already have check_page locked) and mlock_vma_page() is performed only upon success. If the page lock cannot be obtained, the page is left without PG_mlocked, which is again not a problem in the whole unevictable memory design. Signed-off-by: Vlastimil Babka Signed-off-by: Bob Liu Reported-by: Sasha Levin Cc: Wanpeng Li Cc: Michel Lespinasse Cc: KOSAKI Motohiro Acked-by: Rik van Riel Cc: David Rientjes Cc: Mel Gorman Cc: Hugh Dickins Cc: Joonsoo Kim Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds (back ported from commit 57e68e9cd65b4b8eb4045a1e0d0746458502554c) CVE-2014-3122 BugLink: http://bugs.launchpad.net/bugs/1316268 Signed-off-by: Luis Henriques Acked-by: Andy Whitcroft Signed-off-by: Tim Gardner Signed-off-by: Willy Tarreau --- mm/mlock.c | 2 ++ mm/rmap.c | 14 ++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/mm/mlock.c b/mm/mlock.c index 2d846cf..4db29b3 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -78,6 +78,7 @@ void __clear_page_mlock(struct page *page) */ void mlock_vma_page(struct page *page) { + /* Serialize with page migration */ BUG_ON(!PageLocked(page)); if (!TestSetPageMlocked(page)) { @@ -108,6 +109,7 @@ void mlock_vma_page(struct page *page) */ void munlock_vma_page(struct page *page) { + /* For try_to_munlock() and to serialize with page migration */ BUG_ON(!PageLocked(page)); if (TestClearPageMlocked(page)) { diff --git a/mm/rmap.c b/mm/rmap.c index dd43373..cedeae8 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -944,9 +944,19 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, BUG_ON(!page || PageAnon(page)); if (locked_vma) { - mlock_vma_page(page); /* no-op if already mlocked */ - if (page == check_page) + if (page == check_page) { + /* we know we have check_page locked */ + mlock_vma_page(page); ret = SWAP_MLOCK; + } else if (trylock_page(page)) { + /* + * If we can lock the page, perform mlock. + * Otherwise leave the page alone, it will be + * eventually encountered again later. + */ + mlock_vma_page(page); + unlock_page(page); + } continue; /* don't unmap */ } -- 1.7.12.2.21.g234cd45.dirty