btrfs: Verify that every chunk has corresponding block group at mount time

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>

1 files changed, 57 insertions, 1 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 54a0cfef5c5c..de6f75f5547b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -9844,6 +9844,62 @@ btrfs_create_block_group_cache(struct btrfs_fs_info *fs_info,
         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_fs_info *info)
 {
         struct btrfs_path *path;
@@ -10010,7 +10066,7 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
 
         btrfs_add_raid_kobjects(info);
         init_global_block_rsv(info);
-        ret = 0;
+        ret = check_chunk_block_group_mappings(info);
 error:
         btrfs_free_path(path);
         return ret;