btrfs: fix potential oops in device_list_add

Al Viro · kdave · commit 92900e5160a5 · 2019-01-30T18:16:40.000+01:00
alloc_fs_devices() can return ERR_PTR(-ENOMEM), so dereferencing its result before the check for IS_ERR() is a bad idea. Fixes: d1a6300 ("btrfs: add members to fs_devices to track fsid changes") Reviewed-by: Nikolay Borisov <nborisov@suse.com> Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
@@ -957,11 +957,11 @@ static noinline struct btrfs_device *device_list_add(const char *path,
 		else
 			fs_devices = alloc_fs_devices(disk_super->fsid, NULL);
 
-		fs_devices->fsid_change = fsid_change_in_progress;
-
 		if (IS_ERR(fs_devices))
 			return ERR_CAST(fs_devices);
 
+		fs_devices->fsid_change = fsid_change_in_progress;
+
 		mutex_lock(&fs_devices->device_list_mutex);
 		list_add(&fs_devices->fs_list, &fs_uuids);
 
