From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932613Ab3FEVNJ (ORCPT ); Wed, 5 Jun 2013 17:13:09 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36921 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932580Ab3FEVNF (ORCPT ); Wed, 5 Jun 2013 17:13:05 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Brian Behlendorf , Chris Wedgwood , Jens Axboe , Andrew Morton , Linus Torvalds Subject: [ 25/44] drivers/block/brd.c: fix brd_lookup_page() race Date: Wed, 5 Jun 2013 14:12:23 -0700 Message-Id: <20130605211224.514870403@linuxfoundation.org> X-Mailer: git-send-email 1.8.3.rc0.20.gb99dd2e In-Reply-To: <20130605211221.858177087@linuxfoundation.org> References: <20130605211221.858177087@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Brian Behlendorf commit dfd20b2b174d3a9b258ea3b7a35ead33576587b1 upstream. The index on the page must be set before it is inserted in the radix tree. Otherwise there is a small race which can occur during lookup where the page can be found with the incorrect index. This will trigger the BUG_ON() in brd_lookup_page(). Signed-off-by: Brian Behlendorf Reported-by: Chris Wedgwood Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- drivers/block/brd.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -117,13 +117,13 @@ static struct page *brd_insert_page(stru spin_lock(&brd->brd_lock); idx = sector >> PAGE_SECTORS_SHIFT; + page->index = idx; if (radix_tree_insert(&brd->brd_pages, idx, page)) { __free_page(page); page = radix_tree_lookup(&brd->brd_pages, idx); BUG_ON(!page); BUG_ON(page->index != idx); - } else - page->index = idx; + } spin_unlock(&brd->brd_lock); radix_tree_preload_end();