From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp2130.oracle.com ([141.146.126.79]:59564 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752714AbeFFP6c (ORCPT ); Wed, 6 Jun 2018 11:58:32 -0400 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w56FuQaE130689 for ; Wed, 6 Jun 2018 15:58:31 GMT Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by aserp2130.oracle.com with ESMTP id 2jbvyp5b31-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Wed, 06 Jun 2018 15:58:31 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w56FwUCB031018 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Wed, 6 Jun 2018 15:58:31 GMT Received: from abhmp0007.oracle.com (abhmp0007.oracle.com [141.146.116.13]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id w56FwU8X017916 for ; Wed, 6 Jun 2018 15:58:30 GMT From: Anand Jain To: linux-btrfs@vger.kernel.org Subject: [PATCH] btrfs: fix race between free_stale_devices and close_fs_devices Date: Thu, 7 Jun 2018 00:01:09 +0800 Message-Id: <20180606160109.10177-1-anand.jain@oracle.com> In-Reply-To: <000000000000b9e25a056de4dd10@google.com> References: <000000000000b9e25a056de4dd10@google.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: %fs_devices can be free-ed by btrfs_free_stale_devices() when the close_fs_devices() drops fs_devices::opened to zero, but close_fs_devices tries to access the %fs_devices again without the device_list_mutex. Fix this by bringing the %fs_devices access with in the device_list_mutex. Stack trace as below. HEAD commit: 716a685fdb89 Merge branch 'x86-hyperv-for-linus' of git://.. :: CPU: 1 PID: 4499 Comm: syz-executor921 Not tainted 4.17.0+ #84 :: WARNING: CPU: 1 PID: 4499 at fs/btrfs/volumes.c:1071 close_fs_devices+0xbc7/0xfa0 fs/btrfs/volumes.c:1071 Kernel panic - not syncing: panic_on_warn set ... :: RIP: 0010:close_fs_devices+0xbc7/0xfa0 fs/btrfs/volumes.c:1071 :: btrfs_close_devices+0x29/0x150 fs/btrfs/volumes.c:1085 open_ctree+0x589/0x7898 fs/btrfs/disk-io.c:3358 btrfs_fill_super fs/btrfs/super.c:1202 [inline] btrfs_mount_root+0x16df/0x1e70 fs/btrfs/super.c:1593 mount_fs+0xae/0x328 fs/super.c:1277 vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037 vfs_kern_mount+0x40/0x60 fs/namespace.c:1027 btrfs_mount+0x4a1/0x213e fs/btrfs/super.c:1661 mount_fs+0xae/0x328 fs/super.c:1277 Reported-by: syzbot+ceb2606025ec1cc3479c@syzkaller.appspotmail.com Signed-off-by: Anand Jain --- fs/btrfs/volumes.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index c2b7d66192e8..32fba4e24027 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1153,6 +1153,12 @@ static int close_fs_devices(struct btrfs_fs_devices *fs_devices) btrfs_prepare_close_one_device(device); list_add(&device->dev_list, &pending_put); } + + WARN_ON(fs_devices->open_devices); + WARN_ON(fs_devices->rw_devices); + fs_devices->opened = 0; + clear_bit(BTRFS_VOLUME_STATE_SEEDING, &fs_devices->volume_state); + mutex_unlock(&fs_devices->device_list_mutex); /* @@ -1169,11 +1175,6 @@ static int close_fs_devices(struct btrfs_fs_devices *fs_devices) call_rcu(&device->rcu, free_device_rcu); } - WARN_ON(fs_devices->open_devices); - WARN_ON(fs_devices->rw_devices); - fs_devices->opened = 0; - clear_bit(BTRFS_VOLUME_STATE_SEEDING, &fs_devices->volume_state); - return 0; } -- 2.15.0