Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751719AbdHCPCQ (ORCPT ); Thu, 3 Aug 2017 11:02:16 -0400 Received: from bran.ispras.ru ([83.149.199.196]:19555 "EHLO smtp.ispras.ru" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751174AbdHCPCP (ORCPT ); Thu, 3 Aug 2017 11:02:15 -0400 From: Anton Volkov To: tom.leiming@gmail.com Cc: axboe@fb.com, osandov@fb.com, linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org, khoroshilov@ispras.ru, Anton Volkov Subject: [PATCH] loop: fix to a race condition due to the early registration of device Date: Thu, 3 Aug 2017 18:01:38 +0300 Message-Id: <1501772498-28197-1-git-send-email-avolkov@ispras.ru> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1455 Lines: 65 The early device registration made possible a race leading to allocations of disks with wrong minors. This patch moves the device registration further down the loop_init function to make the race infeasible. Found by Linux Driver Verification project (linuxtesting.org). Signed-off-by: Anton Volkov --- drivers/block/loop.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index ef83349..2fbd4089 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1996,10 +1996,6 @@ static int __init loop_init(void) struct loop_device *lo; int err; - err = misc_register(&loop_misc); - if (err < 0) - return err; - part_shift = 0; if (max_part > 0) { part_shift = fls(max_part); @@ -2017,12 +2013,12 @@ static int __init loop_init(void) if ((1UL << part_shift) > DISK_MAX_PARTS) { err = -EINVAL; - goto misc_out; + goto err_out; } if (max_loop > 1UL << (MINORBITS - part_shift)) { err = -EINVAL; - goto misc_out; + goto err_out; } /* @@ -2041,6 +2037,11 @@ static int __init loop_init(void) range = 1UL << MINORBITS; } + err = misc_register(&loop_misc); + if (err < 0) + goto err_out; + + if (register_blkdev(LOOP_MAJOR, "loop")) { err = -EIO; goto misc_out; @@ -2060,6 +2061,7 @@ static int __init loop_init(void) misc_out: misc_deregister(&loop_misc); +err_out: return err; } -- 2.7.4