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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 CDFECC282C3 for ; Thu, 24 Jan 2019 19:46:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 92F07217D7 for ; Thu, 24 Jan 2019 19:46:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548359188; bh=5XogNCR5hXArckQfEckV0c9OUx+oa1z7+HPBu9Ygmmw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=BVIb3lb7MzeMXETr+2moth8FaWhHEwNjQ8i34JQLbsB5tSTphJHCZI6WKoXq5u4wG e7jhL/+zUDRRRHTVZr0S3x740v25dUvSWTUiUfO0pEv4iIp2J0dewuUu3+2ePvXwko cBbh1TuU3rNVwzPXwy/GHAwPIzfx0u5gRr+oAAmE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387884AbfAXTq0 (ORCPT ); Thu, 24 Jan 2019 14:46:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:44736 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388018AbfAXToC (ORCPT ); Thu, 24 Jan 2019 14:44:02 -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 09D0C218D2; Thu, 24 Jan 2019 19:44:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548359041; bh=5XogNCR5hXArckQfEckV0c9OUx+oa1z7+HPBu9Ygmmw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=o18/i18vxYFfTPEnM82gc2aXU4ngK5DhVqBivP0AqLQWueuHbSNyPdP7UM+QHb7oB 3RABJRzNIEyCB4YjizIZEUjgU1Um8HstICb07VxFDswQ+hwYDarv5E2YM36PPaxmGJ wG0ShRSnjgz3j8lXjB2ufwaEiXmFCfWZ5cb0n2dQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Anand Jain , David Sterba , Sasha Levin Subject: [PATCH 4.20 079/127] btrfs: fix use-after-free due to race between replace start and cancel Date: Thu, 24 Jan 2019 20:20:25 +0100 Message-Id: <20190124190215.481301753@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190124190211.984305387@linuxfoundation.org> References: <20190124190211.984305387@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 4.20-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit d189dd70e2556181732598956d808ea53cc8774e ] The device replace cancel thread can race with the replace start thread and if fs_info::scrubs_running is not yet set, btrfs_scrub_cancel() will fail to stop the scrub thread. The scrub thread continues with the scrub for replace which then will try to write to the target device and which is already freed by the cancel thread. scrub_setup_ctx() warns as tgtdev is NULL. struct scrub_ctx *scrub_setup_ctx(struct btrfs_device *dev, int is_dev_replace) { ... if (is_dev_replace) { WARN_ON(!fs_info->dev_replace.tgtdev); <=== sctx->pages_per_wr_bio = SCRUB_PAGES_PER_WR_BIO; sctx->wr_tgtdev = fs_info->dev_replace.tgtdev; sctx->flush_all_writes = false; } [ 6724.497655] BTRFS info (device sdb): dev_replace from /dev/sdb (devid 1) to /dev/sdc started [ 6753.945017] BTRFS info (device sdb): dev_replace from /dev/sdb (devid 1) to /dev/sdc canceled [ 6852.426700] WARNING: CPU: 0 PID: 4494 at fs/btrfs/scrub.c:622 scrub_setup_ctx.isra.19+0x220/0x230 [btrfs] ... [ 6852.428928] RIP: 0010:scrub_setup_ctx.isra.19+0x220/0x230 [btrfs] ... [ 6852.432970] Call Trace: [ 6852.433202] btrfs_scrub_dev+0x19b/0x5c0 [btrfs] [ 6852.433471] btrfs_dev_replace_start+0x48c/0x6a0 [btrfs] [ 6852.433800] btrfs_dev_replace_by_ioctl+0x3a/0x60 [btrfs] [ 6852.434097] btrfs_ioctl+0x2476/0x2d20 [btrfs] [ 6852.434365] ? do_sigaction+0x7d/0x1e0 [ 6852.434623] do_vfs_ioctl+0xa9/0x6c0 [ 6852.434865] ? syscall_trace_enter+0x1c8/0x310 [ 6852.435124] ? syscall_trace_enter+0x1c8/0x310 [ 6852.435387] ksys_ioctl+0x60/0x90 [ 6852.435663] __x64_sys_ioctl+0x16/0x20 [ 6852.435907] do_syscall_64+0x50/0x180 [ 6852.436150] entry_SYSCALL_64_after_hwframe+0x49/0xbe Further, as the replace thread enters scrub_write_page_to_dev_replace() without the target device it panics: static int scrub_add_page_to_wr_bio(struct scrub_ctx *sctx, struct scrub_page *spage) { ... bio_set_dev(bio, sbio->dev->bdev); <====== [ 6929.715145] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0 .. [ 6929.717106] Workqueue: btrfs-scrub btrfs_scrub_helper [btrfs] [ 6929.717420] RIP: 0010:scrub_write_page_to_dev_replace+0xb4/0x260 [btrfs] .. [ 6929.721430] Call Trace: [ 6929.721663] scrub_write_block_to_dev_replace+0x3f/0x60 [btrfs] [ 6929.721975] scrub_bio_end_io_worker+0x1af/0x490 [btrfs] [ 6929.722277] normal_work_helper+0xf0/0x4c0 [btrfs] [ 6929.722552] process_one_work+0x1f4/0x520 [ 6929.722805] ? process_one_work+0x16e/0x520 [ 6929.723063] worker_thread+0x46/0x3d0 [ 6929.723313] kthread+0xf8/0x130 [ 6929.723544] ? process_one_work+0x520/0x520 [ 6929.723800] ? kthread_delayed_work_timer_fn+0x80/0x80 [ 6929.724081] ret_from_fork+0x3a/0x50 Fix this by letting the btrfs_dev_replace_finishing() to do the job of cleaning after the cancel, including freeing of the target device. btrfs_dev_replace_finishing() is called when btrfs_scub_dev() returns along with the scrub return status. Signed-off-by: Anand Jain Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/dev-replace.c | 63 +++++++++++++++++++++++++++--------------- 1 file changed, 41 insertions(+), 22 deletions(-) diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 329d3afcf304..65e4b8637638 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -797,39 +797,58 @@ int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info) case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED: result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED; btrfs_dev_replace_write_unlock(dev_replace); - goto leave; + break; case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED: + result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR; + tgt_device = dev_replace->tgtdev; + src_device = dev_replace->srcdev; + btrfs_dev_replace_write_unlock(dev_replace); + btrfs_scrub_cancel(fs_info); + /* btrfs_dev_replace_finishing() will handle the cleanup part */ + btrfs_info_in_rcu(fs_info, + "dev_replace from %s (devid %llu) to %s canceled", + btrfs_dev_name(src_device), src_device->devid, + btrfs_dev_name(tgt_device)); + break; case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED: + /* + * Scrub doing the replace isn't running so we need to do the + * cleanup step of btrfs_dev_replace_finishing() here + */ result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR; tgt_device = dev_replace->tgtdev; src_device = dev_replace->srcdev; dev_replace->tgtdev = NULL; dev_replace->srcdev = NULL; - break; - } - dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED; - dev_replace->time_stopped = ktime_get_real_seconds(); - dev_replace->item_needs_writeback = 1; - btrfs_dev_replace_write_unlock(dev_replace); - btrfs_scrub_cancel(fs_info); + dev_replace->replace_state = + BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED; + dev_replace->time_stopped = ktime_get_real_seconds(); + dev_replace->item_needs_writeback = 1; - trans = btrfs_start_transaction(root, 0); - if (IS_ERR(trans)) { - mutex_unlock(&dev_replace->lock_finishing_cancel_unmount); - return PTR_ERR(trans); - } - ret = btrfs_commit_transaction(trans); - WARN_ON(ret); + btrfs_dev_replace_write_unlock(dev_replace); - btrfs_info_in_rcu(fs_info, - "dev_replace from %s (devid %llu) to %s canceled", - btrfs_dev_name(src_device), src_device->devid, - btrfs_dev_name(tgt_device)); + btrfs_scrub_cancel(fs_info); + + trans = btrfs_start_transaction(root, 0); + if (IS_ERR(trans)) { + mutex_unlock(&dev_replace->lock_finishing_cancel_unmount); + return PTR_ERR(trans); + } + ret = btrfs_commit_transaction(trans); + WARN_ON(ret); - if (tgt_device) - btrfs_destroy_dev_replace_tgtdev(tgt_device); + btrfs_info_in_rcu(fs_info, + "suspended dev_replace from %s (devid %llu) to %s canceled", + btrfs_dev_name(src_device), src_device->devid, + btrfs_dev_name(tgt_device)); + + if (tgt_device) + btrfs_destroy_dev_replace_tgtdev(tgt_device); + break; + default: + result = -EINVAL; + } -leave: mutex_unlock(&dev_replace->lock_finishing_cancel_unmount); return result; } -- 2.19.1