[PATCH AUTOSEL 5.4 18/23] btrfs: handle chunk tree lookup error in btrfs_relocate_sys_chunks()

Sasha Levin
2024-03-29T12:50:43Z

From: David Sterba <dsterba@suse.com>

[ Upstream commit 7411055db5ce64f836aaffd422396af0075fdc99 ]

The unhandled case in btrfs_relocate_sys_chunks() loop is a corruption,
as it could be caused only by two impossible conditions:

- at first the search key is set up to look for a chunk tree item, with
offset -1, this is an inexact search and the key->offset will contain
the correct offset upon a successful search, a valid chunk tree item
cannot have an offset -1

- after first successful search, the found_key corresponds to a chunk
item, the offset is decremented by 1 before the next loop, it's
impossible to find a chunk item there due to alignment and size
constraints

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/volumes.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e11c8da9a5605..b5873df0aa93a 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3268,7 +3268,17 @@ static int btrfs_relocate_sys_chunks(struct btrfs_fs_info *fs_info)
mutex_unlock(&fs_info->delete_unused_bgs_mutex);
goto error;
}
- BUG_ON(ret == 0); /* Corruption */
+ if (ret == 0) {
+ /*
+ * On the first search we would find chunk tree with
+ * offset -1, which is not possible. On subsequent
+ * loops this would find an existing item on an invalid
+ * offset (one less than the previous one, wrong
+ * alignment and size).
+ */
+ ret = -EUCLEAN;
+ goto error;
+ }

ret = btrfs_previous_item(chunk_root, path, key.objectid,
key.type);
--
2.43.0