From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755351AbbCFKTF (ORCPT ); Fri, 6 Mar 2015 05:19:05 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:44693 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933183AbbCFKAn (ORCPT ); Fri, 6 Mar 2015 05:00:43 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Mikulas Patocka , Mike Snitzer , Luis Henriques Subject: [PATCH 3.16.y-ckt 135/183] dm snapshot: fix a possible invalid memory access on unload Date: Fri, 6 Mar 2015 09:57:06 +0000 Message-Id: <1425635874-19087-136-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1425635874-19087-1-git-send-email-luis.henriques@canonical.com> References: <1425635874-19087-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt8 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikulas Patocka commit 22aa66a3ee5b61e0f4a0bfeabcaa567861109ec3 upstream. When the snapshot target is unloaded, snapshot_dtr() waits until pending_exceptions_count drops to zero. Then, it destroys the snapshot. Therefore, the function that decrements pending_exceptions_count should not touch the snapshot structure after the decrement. pending_complete() calls free_pending_exception(), which decrements pending_exceptions_count, and then it performs up_write(&s->lock) and it calls retry_origin_bios() which dereferences s->origin. These two memory accesses to the fields of the snapshot may touch the dm_snapshot struture after it is freed. This patch moves the call to free_pending_exception() to the end of pending_complete(), so that the snapshot will not be destroyed while pending_complete() is in progress. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Luis Henriques --- drivers/md/dm-snap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 5bd2290cfb1e..8380d036eec3 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1440,8 +1440,6 @@ out: full_bio->bi_private = pe->full_bio_private; atomic_inc(&full_bio->bi_remaining); } - free_pending_exception(pe); - increment_pending_exceptions_done_count(); up_write(&s->lock); @@ -1458,6 +1456,8 @@ out: } retry_origin_bios(s, origin_bios); + + free_pending_exception(pe); } static void commit_callback(void *context, int success)