From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756160Ab3FDOIY (ORCPT ); Tue, 4 Jun 2013 10:08:24 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:46791 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754869Ab3FDOIM (ORCPT ); Tue, 4 Jun 2013 10:08:12 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Brian Behlendorf , Jens Axboe , Andrew Morton , Linus Torvalds , Luis Henriques Subject: [PATCH 34/70] drivers/block/brd.c: fix brd_lookup_page() race Date: Tue, 4 Jun 2013 15:06:50 +0100 Message-Id: <1370354846-14213-35-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1370354846-14213-1-git-send-email-luis.henriques@canonical.com> References: <1370354846-14213-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.5.7.14 -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: Luis Henriques --- drivers/block/brd.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/block/brd.c b/drivers/block/brd.c index 531ceb3..4e8213a 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -117,13 +117,13 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector) 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(); -- 1.8.1.2