From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with ESMTP id C27E562000E for ; Fri, 12 Feb 2010 07:01:05 -0500 (EST) From: Mel Gorman 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> 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: owner-linux-mm@kvack.org 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 List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org