[PATCH 3.16 052/245] btrfs: Verify that every chunk has corresponding block group at mount time

Ben Hutchings
2020-04-23T23:21:31Z

From: Qu Wenruo <wqu@suse.com>

commit 7ef49515fa6727cb4b6f2f5b0ffbc5fc20a9f8c6 upstream.

If a crafted image has missing block group items, it could cause
unexpected behavior and breaks the assumption of 1:1 chunk<->block group
mapping.

Although we have the block group -> chunk mapping check, we still need
chunk -> block group mapping check.

This patch will do extra check to ensure each chunk has its
corresponding block group.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=199847
Reported-by: Xu Wen <wen.xu@gatech.edu>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Gu Jinxiang <gujx@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/btrfs/extent-tree.c | 58 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 57 insertions(+), 1 deletion(-)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8819,6 +8819,62 @@ btrfs_create_block_group_cache(struct bt
return cache;
}

+
+/*
+ * Iterate all chunks and verify that each of them has the corresponding block
+ * group
+ */
+static int check_chunk_block_group_mappings(struct btrfs_fs_info *fs_info)
+{
+ struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
+ struct extent_map *em;
+ struct btrfs_block_group_cache *bg;
+ u64 start = 0;
+ int ret = 0;
+
+ while (1) {
+ read_lock(&map_tree->map_tree.lock);
+ /*
+ * lookup_extent_mapping will return the first extent map
+ * intersecting the range, so setting @len to 1 is enough to
+ * get the first chunk.
+ */
+ em = lookup_extent_mapping(&map_tree->map_tree, start, 1);
+ read_unlock(&map_tree->map_tree.lock);
+ if (!em)
+ break;
+
+ bg = btrfs_lookup_block_group(fs_info, em->start);
+ if (!bg) {
+ btrfs_err(fs_info,
+ "chunk start=%llu len=%llu doesn't have corresponding block group",
+ em->start, em->len);
+ ret = -EUCLEAN;
+ free_extent_map(em);
+ break;
+ }
+ if (bg->key.objectid != em->start ||
+ bg->key.offset != em->len ||
+ (bg->flags & BTRFS_BLOCK_GROUP_TYPE_MASK) !=
+ (em->map_lookup->type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
+ btrfs_err(fs_info,
+"chunk start=%llu len=%llu flags=0x%llx doesn't match block group start=%llu len=%llu flags=0x%llx",
+ em->start, em->len,
+ em->map_lookup->type & BTRFS_BLOCK_GROUP_TYPE_MASK,
+ bg->key.objectid, bg->key.offset,
+ bg->flags & BTRFS_BLOCK_GROUP_TYPE_MASK);
+ ret = -EUCLEAN;
+ free_extent_map(em);
+ btrfs_put_block_group(bg);
+ break;
+ }
+ start = em->start + em->len;
+ free_extent_map(em);
+ btrfs_put_block_group(bg);
+ }
+ return ret;
+}
+
int btrfs_read_block_groups(struct btrfs_root *root)
{
struct btrfs_path *path;
@@ -8981,7 +9037,7 @@ int btrfs_read_block_groups(struct btrfs
}

init_global_block_rsv(info);
- ret = 0;
+ ret = check_chunk_block_group_mappings(info);
error:
btrfs_free_path(path);
return ret;