Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756838Ab0BLMCL (ORCPT ); Fri, 12 Feb 2010 07:02:11 -0500 Received: from gir.skynet.ie ([193.1.99.77]:55587 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751206Ab0BLMBG (ORCPT ); Fri, 12 Feb 2010 07:01:06 -0500 From: Mel Gorman To: Andrea Arcangeli Cc: Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , KOSAKI Motohiro , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 11/12] mm: Take the RCU read lock in rmap_walk_anon Date: Fri, 12 Feb 2010 12:00:58 +0000 Message-Id: <1265976059-7459-12-git-send-email-mel@csn.ul.ie> X-Mailer: git-send-email 1.6.5 In-Reply-To: <1265976059-7459-1-git-send-email-mel@csn.ul.ie> References: <1265976059-7459-1-git-send-email-mel@csn.ul.ie> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1612 Lines: 50 rmap_walk_anon() does not use page_lock_anon_vma() for looking up and locking an anon_vma. One important difference between page_lock_anon_vma() and rmap_walk_anon() is that the page_lock_anon_vma() takes the RCU lock before the lookup so that the anon_vma does not disappear. There does not appear to be locking in place that prevents the anon_vma disappearing before the spinlock is taken. This patch puts a rcu_read_lock() around the anon_vma lookup similar to what page_lock_anon_vma() does to prevent an accidental use-after-free. Signed-off-by: Mel Gorman --- mm/rmap.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index b468d5f..fb695d3 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1233,9 +1233,10 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *, * This needs to be reviewed later: avoiding page_lock_anon_vma() * is risky, and currently limits the usefulness of rmap_walk(). */ + rcu_read_lock(); anon_vma = page_anon_vma(page); if (!anon_vma) - return ret; + goto out_rcu_unlock; spin_lock(&anon_vma->lock); /* @@ -1256,6 +1257,10 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *, out_anon_unlock: spin_unlock(&anon_vma->lock); + +out_rcu_unlock: + rcu_read_unlock(); + return ret; } -- 1.6.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/