Messages in this thread Patch in this message |  | | From | Desmond Cheong Zhi Xi <> | Subject | [PATCH] btrfs: fix rw device counting in __btrfs_free_extra_devids | Date | Thu, 15 Jul 2021 18:34:03 +0800 |
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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
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