From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> To: clm@fb.com, josef@toxicpanda.com, dsterba@suse.com Cc: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>, anand.jain@oracle.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org, syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com Subject: [PATCH] btrfs: fix rw device counting in __btrfs_free_extra_devids Date: Thu, 15 Jul 2021 18:34:03 +0800 [thread overview] Message-ID: <20210715103403.176695-1-desmondcheongzx@gmail.com> (raw) Syzbot reports a warning in close_fs_devices that happens because fs_devices->rw_devices is not 0 after calling btrfs_close_one_device on each device. This happens when a writeable device is removed in __btrfs_free_extra_devids, but the rw device count is not decremented accordingly. So when close_fs_devices is called, the removed device is still counted and we get an off by 1 error. Here is one call trace that was observed: btrfs_mount_root(): btrfs_scan_one_device(): device_list_add(); <---------------- device added btrfs_open_devices(): open_fs_devices(): btrfs_open_one_device(); <-------- rw device count ++ btrfs_fill_super(): open_ctree(): btrfs_free_extra_devids(): __btrfs_free_extra_devids(); <--- device removed fail_tree_roots: btrfs_close_devices(): close_fs_devices(); <------- rw device count off by 1 Fixes: cf89af146b7e ("btrfs: dev-replace: fail mount if we don't have replace item with target device") Reported-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com Tested-by: syzbot+a70e2ad0879f160b9217@syzkaller.appspotmail.com Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> --- fs/btrfs/volumes.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 807502cd6510..916c25371658 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1078,6 +1078,7 @@ static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) { list_del_init(&device->dev_alloc_list); clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state); + fs_devices->rw_devices--; } list_del_init(&device->dev_list); fs_devices->num_devices--; -- 2.25.1
next reply other threads:[~2021-07-15 10:34 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-15 10:34 Desmond Cheong Zhi Xi [this message] 2021-07-15 11:23 ` Anand Jain 2021-07-15 11:55 ` Nikolay Borisov 2021-07-15 13:11 ` Desmond Cheong Zhi Xi 2021-07-21 13:34 ` David Sterba 2021-07-21 17:59 ` David Sterba 2021-07-25 6:19 ` Desmond Cheong Zhi Xi 2021-07-26 17:52 ` David Sterba 2021-07-26 23:07 ` Desmond Cheong Zhi Xi 2021-07-25 13:49 ` Anand Jain
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