From patchwork Thu Feb 6 11:10:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 11368249 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 36D0E1398 for ; Thu, 6 Feb 2020 11:12:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1FC2C21741 for ; Thu, 6 Feb 2020 11:12:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727561AbgBFLMF (ORCPT ); Thu, 6 Feb 2020 06:12:05 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:36448 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727560AbgBFLMF (ORCPT ); Thu, 6 Feb 2020 06:12:05 -0500 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 90BFE2624F6B1E4B9F84; Thu, 6 Feb 2020 19:11:55 +0800 (CST) Received: from huawei.com (10.175.124.28) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.439.0; Thu, 6 Feb 2020 19:11:46 +0800 From: yu kuai To: , , , , , , , CC: , , , , , Subject: [PATCH] block: revert pushing the final release of request_queue to a workqueue. Date: Thu, 6 Feb 2020 19:10:52 +0800 Message-ID: <20200206111052.45356-1-yukuai3@huawei.com> X-Mailer: git-send-email 2.17.2 MIME-Version: 1.0 X-Originating-IP: [10.175.124.28] X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org syzbot is reporting use after free bug in debugfs_remove[1]. This is because in request_queue, 'q->debugfs_dir' and 'q->blk_trace->dir' could be the same dir. And in __blk_release_queue(), blk_mq_debugfs_unregister() will remove everything inside the dir. With futher investigation of the reporduce repro, the problem can be reporduced by following procedure: 1. LOOP_CTL_ADD, create a request_queue q1, blk_mq_debugfs_register() will create the dir. 2. LOOP_CTL_REMOVE, blk_release_queue() will add q1 to release queue. 3. LOOP_CTL_ADD, create another request_queue q2,blk_mq_debugfs_register() will fail because the dir aready exist. 4. BLKTRACESETUP, create two files(msg and dropped) inside the dir. 5. call __blk_release_queue() for q1, debugfs_remove_recursive() will delete the files created in step 4. 6. LOOP_CTL_REMOVE, blk_release_queue() will add q2 to release queue. And when __blk_release_queue() is called for q2, blk_trace_shutdown() will try to release the two files created in step 4, wich are aready released in step 5. |thread1 |kworker |thread2 | | ----------------------- | ------------------------ | -------------------- | |loop_control_ioctl | | | | loop_add | | | | blk_mq_debugfs_register| | | | debugfs_create_dir | | | |loop_control_ioctl | | | | loop_remove | | | | blk_release_queue | | | | schedule_work | | | | | |loop_control_ioctl | | | | loop_add | | | | ... | | | |blk_trace_ioctl | | | | __blk_trace_setup | | | | debugfs_create_file| | |__blk_release_queue | | | | blk_mq_debugfs_unregister| | | | debugfs_remove_recursive| | | | |loop_control_ioctl | | | | loop_remove | | | | ... | | |__blk_release_queue | | | | blk_trace_shutdown | | | | debugfs_remove | | commit dc9edc44de6c ("block: Fix a blk_exit_rl() regression") pushed the final release of request_queue to a workqueue, witch is not necessary since commit 1e9364283764 ("blk-sysfs: Rework documention of __blk_release_queue"). [1] https://syzkaller.appspot.com/bug?extid=903b72a010ad6b7a40f2 References: CVE-2019-19770 Fixes: commit dc9edc44de6c ("block: Fix a blk_exit_rl() regression") Reported-by: syzbot Signed-off-by: yu kuai --- block/blk-sysfs.c | 18 +++++------------- include/linux/blkdev.h | 2 -- 2 files changed, 5 insertions(+), 15 deletions(-) diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index fca9b158f4a0..3f448292099d 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -862,8 +862,8 @@ static void blk_exit_queue(struct request_queue *q) /** - * __blk_release_queue - release a request queue - * @work: pointer to the release_work member of the request queue to be released + * blk_release_queue - release a request queue + * @@kobj: the kobj belonging to the request queue to be released * * Description: * This function is called when a block device is being unregistered. The @@ -873,9 +873,10 @@ static void blk_exit_queue(struct request_queue *q) * of the request queue reaches zero, blk_release_queue is called to release * all allocated resources of the request queue. */ -static void __blk_release_queue(struct work_struct *work) +static void blk_release_queue(struct kobject *kobj) { - struct request_queue *q = container_of(work, typeof(*q), release_work); + struct request_queue *q = + container_of(kobj, struct request_queue, kobj); if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags)) blk_stat_remove_callback(q, q->poll_cb); @@ -904,15 +905,6 @@ static void __blk_release_queue(struct work_struct *work) call_rcu(&q->rcu_head, blk_free_queue_rcu); } -static void blk_release_queue(struct kobject *kobj) -{ - struct request_queue *q = - container_of(kobj, struct request_queue, kobj); - - INIT_WORK(&q->release_work, __blk_release_queue); - schedule_work(&q->release_work); -} - static const struct sysfs_ops queue_sysfs_ops = { .show = queue_attr_show, .store = queue_attr_store, diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 04cfa798a365..dff4d032c78a 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -580,8 +580,6 @@ struct request_queue { size_t cmd_size; - struct work_struct release_work; - #define BLK_MAX_WRITE_HINTS 5 u64 write_hints[BLK_MAX_WRITE_HINTS]; };