btrfs: tree-checker: Add ROOT_ITEM check

This patch will introduce ROOT_ITEM check, which includes:
- Key->objectid and key->offset check
  Currently only some easy check, e.g. 0 as rootid is invalid.

- Item size check
  Root item size is fixed.

- Generation checks
  Generation, generation_v2 and last_snapshot should not be greater than
  super generation + 1

- Level and alignment check
  Level should be in [0, 7], and bytenr must be aligned to sector size.

- Flags check

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203261
Reported-by: Jungyeon Yoon <jungyeon.yoon@gmail.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 92 insertions, 0 deletions

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index ccd5706199d7..d83adda6c090 100644
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -821,6 +821,95 @@ static int check_inode_item(struct extent_buffer *leaf,
         return 0;
 }
 
+static int check_root_item(struct extent_buffer *leaf, struct btrfs_key *key,
+                           int slot)
+{
+        struct btrfs_fs_info *fs_info = leaf->fs_info;
+        struct btrfs_root_item ri;
+        const u64 valid_root_flags = BTRFS_ROOT_SUBVOL_RDONLY |
+                                     BTRFS_ROOT_SUBVOL_DEAD;
+
+        /* No such tree id */
+        if (key->objectid == 0) {
+                generic_err(leaf, slot, "invalid root id 0");
+                return -EUCLEAN;
+        }
+
+        /*
+         * Some older kernel may create ROOT_ITEM with non-zero offset, so here
+         * we only check offset for reloc tree whose key->offset must be a
+         * valid tree.
+         */
+        if (key->objectid == BTRFS_TREE_RELOC_OBJECTID && key->offset == 0) {
+                generic_err(leaf, slot, "invalid root id 0 for reloc tree");
+                return -EUCLEAN;
+        }
+
+        if (btrfs_item_size_nr(leaf, slot) != sizeof(ri)) {
+                generic_err(leaf, slot,
+                            "invalid root item size, have %u expect %zu",
+                            btrfs_item_size_nr(leaf, slot), sizeof(ri));
+        }
+
+        read_extent_buffer(leaf, &ri, btrfs_item_ptr_offset(leaf, slot),
+                           sizeof(ri));
+
+        /* Generation related */
+        if (btrfs_root_generation(&ri) >
+            btrfs_super_generation(fs_info->super_copy) + 1) {
+                generic_err(leaf, slot,
+                        "invalid root generation, have %llu expect (0, %llu]",
+                            btrfs_root_generation(&ri),
+                            btrfs_super_generation(fs_info->super_copy) + 1);
+                return -EUCLEAN;
+        }
+        if (btrfs_root_generation_v2(&ri) >
+            btrfs_super_generation(fs_info->super_copy) + 1) {
+                generic_err(leaf, slot,
+                "invalid root v2 generation, have %llu expect (0, %llu]",
+                            btrfs_root_generation_v2(&ri),
+                            btrfs_super_generation(fs_info->super_copy) + 1);
+                return -EUCLEAN;
+        }
+        if (btrfs_root_last_snapshot(&ri) >
+            btrfs_super_generation(fs_info->super_copy) + 1) {
+                generic_err(leaf, slot,
+                "invalid root last_snapshot, have %llu expect (0, %llu]",
+                            btrfs_root_last_snapshot(&ri),
+                            btrfs_super_generation(fs_info->super_copy) + 1);
+                return -EUCLEAN;
+        }
+
+        /* Alignment and level check */
+        if (!IS_ALIGNED(btrfs_root_bytenr(&ri), fs_info->sectorsize)) {
+                generic_err(leaf, slot,
+                "invalid root bytenr, have %llu expect to be aligned to %u",
+                            btrfs_root_bytenr(&ri), fs_info->sectorsize);
+                return -EUCLEAN;
+        }
+        if (btrfs_root_level(&ri) >= BTRFS_MAX_LEVEL) {
+                generic_err(leaf, slot,
+                            "invalid root level, have %u expect [0, %u]",
+                            btrfs_root_level(&ri), BTRFS_MAX_LEVEL - 1);
+                return -EUCLEAN;
+        }
+        if (ri.drop_level >= BTRFS_MAX_LEVEL) {
+                generic_err(leaf, slot,
+                            "invalid root level, have %u expect [0, %u]",
+                            ri.drop_level, BTRFS_MAX_LEVEL - 1);
+                return -EUCLEAN;
+        }
+
+        /* Flags check */
+        if (btrfs_root_flags(&ri) & ~valid_root_flags) {
+                generic_err(leaf, slot,
+                            "invalid root flags, have 0x%llx expect mask 0x%llx",
+                            btrfs_root_flags(&ri), valid_root_flags);
+                return -EUCLEAN;
+        }
+        return 0;
+}
+
 /*
  * Common point to switch the item-specific validation.
  */
@@ -856,6 +945,9 @@ static int check_leaf_item(struct extent_buffer *leaf,
         case BTRFS_INODE_ITEM_KEY:
                 ret = check_inode_item(leaf, key, slot);
                 break;
+        case BTRFS_ROOT_ITEM_KEY:
+                ret = check_root_item(leaf, key, slot);
+                break;
         }
         return ret;
 }