From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5DE68C2F3A0 for ; Mon, 21 Jan 2019 14:02:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D6ED214D8 for ; Mon, 21 Jan 2019 14:02:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548079347; bh=zIPpn21egJuWOIqBggnzXGrNNGl/ihuC4Vqo6gkTAmA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=azVAl2i2QvdvAvb9bR7RpEgHMuBYRiwqjFzA/zUeUtsiYq6zHdQhYT/+WSZjmvI/L 6IX60kLMQXfbhWry3KBB/7dxos18/TBye5fsAZ2I8DIsHkQFwekYR6HH1THAmmolSG m6FiNHSzQRscdeh2MyTUGpfBh/8Hm7+1pgm81++w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732798AbfAUOC0 (ORCPT ); Mon, 21 Jan 2019 09:02:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:49896 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732785AbfAUOCX (ORCPT ); Mon, 21 Jan 2019 09:02:23 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 839B72089F; Mon, 21 Jan 2019 14:02:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548079343; bh=zIPpn21egJuWOIqBggnzXGrNNGl/ihuC4Vqo6gkTAmA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zmao1wq6cJfZwg4h+MfCVoFJHs/BcHC2N6JVMUWjGHN1jZIJCFEHwqRWLc/ImMpff NbLnMrodrbvwWkUs8vb1VznPlKntmZxA9jO32MsSaKxnTwsgeuiSvG8w9yR7PIWXdI hih4HuWO/n1Qs+IYa2NJ2aANmNWHgRbMRCaBTmRA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot , Jan Kara , Jens Axboe Subject: [PATCH 4.19 92/99] loop: Move loop_reread_partitions() out of loop_ctl_mutex Date: Mon, 21 Jan 2019 14:49:24 +0100 Message-Id: <20190121134918.446576812@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190121134913.924726465@linuxfoundation.org> References: <20190121134913.924726465@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit 85b0a54a82e4fbceeb1aebb7cb6909edd1a24668 upstream. Calling loop_reread_partitions() under loop_ctl_mutex causes lockdep to complain about circular lock dependency between bdev->bd_mutex and lo->lo_ctl_mutex. The problem is that on loop device open or close lo_open() and lo_release() get called with bdev->bd_mutex held and they need to acquire loop_ctl_mutex. OTOH when loop_reread_partitions() is called with loop_ctl_mutex held, it will call blkdev_reread_part() which acquires bdev->bd_mutex. See syzbot report for details [1]. Move all calls of loop_rescan_partitions() out of loop_ctl_mutex to avoid lockdep warning and fix deadlock possibility. [1] https://syzkaller.appspot.com/bug?id=bf154052f0eea4bc7712499e4569505907d1588 Reported-by: syzbot Signed-off-by: Jan Kara Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/block/loop.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -680,6 +680,7 @@ static int loop_change_fd(struct loop_de { struct file *file, *old_file; int error; + bool partscan; error = mutex_lock_killable_nested(&loop_ctl_mutex, 1); if (error) @@ -721,9 +722,10 @@ static int loop_change_fd(struct loop_de blk_mq_unfreeze_queue(lo->lo_queue); fput(old_file); - if (lo->lo_flags & LO_FLAGS_PARTSCAN) - loop_reread_partitions(lo, bdev); + partscan = lo->lo_flags & LO_FLAGS_PARTSCAN; mutex_unlock(&loop_ctl_mutex); + if (partscan) + loop_reread_partitions(lo, bdev); return 0; out_putf: @@ -904,6 +906,7 @@ static int loop_set_fd(struct loop_devic int lo_flags = 0; int error; loff_t size; + bool partscan; /* This is safe, since we have a reference from open(). */ __module_get(THIS_MODULE); @@ -970,14 +973,15 @@ static int loop_set_fd(struct loop_devic lo->lo_state = Lo_bound; if (part_shift) lo->lo_flags |= LO_FLAGS_PARTSCAN; - if (lo->lo_flags & LO_FLAGS_PARTSCAN) - loop_reread_partitions(lo, bdev); + partscan = lo->lo_flags & LO_FLAGS_PARTSCAN; /* Grab the block_device to prevent its destruction after we * put /dev/loopXX inode. Later in __loop_clr_fd() we bdput(bdev). */ bdgrab(bdev); mutex_unlock(&loop_ctl_mutex); + if (partscan) + loop_reread_partitions(lo, bdev); return 0; out_unlock: @@ -1158,6 +1162,8 @@ loop_set_status(struct loop_device *lo, int err; struct loop_func_table *xfer; kuid_t uid = current_uid(); + struct block_device *bdev; + bool partscan = false; err = mutex_lock_killable_nested(&loop_ctl_mutex, 1); if (err) @@ -1246,10 +1252,13 @@ out_unfreeze: !(lo->lo_flags & LO_FLAGS_PARTSCAN)) { lo->lo_flags |= LO_FLAGS_PARTSCAN; lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN; - loop_reread_partitions(lo, lo->lo_device); + bdev = lo->lo_device; + partscan = true; } out_unlock: mutex_unlock(&loop_ctl_mutex); + if (partscan) + loop_reread_partitions(lo, bdev); return err; }