From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1468877-1518325405-2-17669670138557234105 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1518325404; b=dh7ppBFAo8Q3s+deVuNgfHAdkbDwHpHC7WSez2avInwysBe heqTcxOMZIprdhE3jF3ctAK7+EF3DdAyUPHuzCQSLnvE/HhE0HOF3DvSAsREo+16 ht5377L4x1L0uhTlbg+BKvY3lHyG1wT2bBnELwbEtq/2nk8UTPFIhuoJoXDJwE0w OLvyRKgjR3mZHR5KdEPuAoR3Qyznh/6udA9iSVXK18013ghZHliaJkKhnSvl3U3F bC3CLwypJryxUhFfC5RK9kZ3esJAqq6GhgrKcAzntKg+m+TshOPt7UsRiIsvy1zb Ng/+xJhujB4U+hZOttNirsQEBU6B1JNg4rUK6nQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-type:content-transfer-encoding :mime-version:from:to:cc:date:message-id:subject:in-reply-to :sender:list-id; s=arctest; t=1518325404; bh=1GdlTN34VTm5RlQyxmR HgSNfP+1eIYXtOaIS1ilGyV0=; b=vIajKcubdKrxY7kFzwypcGk8y1uQ5TW5Ndj lHZu5MEPoEWX/4dfh+aKBEXqE9+VikeWBpTYAMq8Kb74q3Ia/3yg2wN5maKgJYqV fYWvHn8mr0TSakIFYuCTHtBSpNNGLGIuUyLXQBEW8UZZgksA1doK6Xc42mO1k28N cFrgeuyOEpGnuSe9pXcIvtxrHQLrCl3KwDFU61Ms5QVs02I3uv3lwnWx23cnP1hI K4ozqPDjzEOd/HDpWzDbZWu8AF85/PIu0kMC29Bj63YcvyUgM5fiNzJ9FmjQUGxS Z7o+72zij1QmBle0Q0Erb+0RWcydPiH+M4CPFtIf4C62qEHvz+Q== ARC-Authentication-Results: i=1; mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Authentication-Results: mx6.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753439AbeBKFCK (ORCPT ); Sun, 11 Feb 2018 00:02:10 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41613 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752751AbeBKEdq (ORCPT ); Sat, 10 Feb 2018 23:33:46 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Christoph Hellwig" , "Waiman Long" , "Steven Rostedt (VMware)" , "Jens Axboe" Date: Sun, 11 Feb 2018 04:20:06 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 35/79] blktrace: Fix potential deadlock between delete & sysfs ops In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.2.99-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Waiman Long commit 5acb3cc2c2e9d3020a4fee43763c6463767f1572 upstream. The lockdep code had reported the following unsafe locking scenario: CPU0 CPU1 ---- ---- lock(s_active#228); lock(&bdev->bd_mutex/1); lock(s_active#228); lock(&bdev->bd_mutex); *** DEADLOCK *** The deadlock may happen when one task (CPU1) is trying to delete a partition in a block device and another task (CPU0) is accessing tracing sysfs file (e.g. /sys/block/dm-1/trace/act_mask) in that partition. The s_active isn't an actual lock. It is a reference count (kn->count) on the sysfs (kernfs) file. Removal of a sysfs file, however, require a wait until all the references are gone. The reference count is treated like a rwsem using lockdep instrumentation code. The fact that a thread is in the sysfs callback method or in the ioctl call means there is a reference to the opended sysfs or device file. That should prevent the underlying block structure from being removed. Instead of using bd_mutex in the block_device structure, a new blk_trace_mutex is now added to the request_queue structure to protect access to the blk_trace structure. Suggested-by: Christoph Hellwig Signed-off-by: Waiman Long Acked-by: Steven Rostedt (VMware) Fix typo in patch subject line, and prune a comment detailing how the code used to work. Signed-off-by: Jens Axboe Signed-off-by: Ben Hutchings --- block/blk-core.c | 3 +++ include/linux/blkdev.h | 1 + kernel/trace/blktrace.c | 18 ++++++++++++------ 3 files changed, 16 insertions(+), 6 deletions(-) --- a/block/blk-core.c +++ b/block/blk-core.c @@ -499,6 +499,9 @@ struct request_queue *blk_alloc_queue_no kobject_init(&q->kobj, &blk_queue_ktype); +#ifdef CONFIG_BLK_DEV_IO_TRACE + mutex_init(&q->blk_trace_mutex); +#endif mutex_init(&q->sysfs_lock); spin_lock_init(&q->__queue_lock); --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -361,6 +361,7 @@ struct request_queue { int node; #ifdef CONFIG_BLK_DEV_IO_TRACE struct blk_trace *blk_trace; + struct mutex blk_trace_mutex; #endif /* * for flush operations --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -631,6 +631,12 @@ int blk_trace_startstop(struct request_q } EXPORT_SYMBOL_GPL(blk_trace_startstop); +/* + * When reading or writing the blktrace sysfs files, the references to the + * opened sysfs or device files should prevent the underlying block device + * from being removed. So no further delete protection is really needed. + */ + /** * blk_trace_ioctl: - handle the ioctls associated with tracing * @bdev: the block device @@ -648,7 +654,7 @@ int blk_trace_ioctl(struct block_device if (!q) return -ENXIO; - mutex_lock(&bdev->bd_mutex); + mutex_lock(&q->blk_trace_mutex); switch (cmd) { case BLKTRACESETUP: @@ -674,7 +680,7 @@ int blk_trace_ioctl(struct block_device break; } - mutex_unlock(&bdev->bd_mutex); + mutex_unlock(&q->blk_trace_mutex); return ret; } @@ -1660,7 +1666,7 @@ static ssize_t sysfs_blk_trace_attr_show if (q == NULL) goto out_bdput; - mutex_lock(&bdev->bd_mutex); + mutex_lock(&q->blk_trace_mutex); if (attr == &dev_attr_enable) { ret = sprintf(buf, "%u\n", !!q->blk_trace); @@ -1679,7 +1685,7 @@ static ssize_t sysfs_blk_trace_attr_show ret = sprintf(buf, "%llu\n", q->blk_trace->end_lba); out_unlock_bdev: - mutex_unlock(&bdev->bd_mutex); + mutex_unlock(&q->blk_trace_mutex); out_bdput: bdput(bdev); out: @@ -1721,7 +1727,7 @@ static ssize_t sysfs_blk_trace_attr_stor if (q == NULL) goto out_bdput; - mutex_lock(&bdev->bd_mutex); + mutex_lock(&q->blk_trace_mutex); if (attr == &dev_attr_enable) { if (value) @@ -1747,7 +1753,7 @@ static ssize_t sysfs_blk_trace_attr_stor } out_unlock_bdev: - mutex_unlock(&bdev->bd_mutex); + mutex_unlock(&q->blk_trace_mutex); out_bdput: bdput(bdev); out: