btrfs: tree-checker: Add EXTENT_ITEM and METADATA_ITEM check

This patch introduces the ability to check extent items.

This check involves:
- key->objectid check
  Basic alignment check.

- key->type check
  Against btrfs_extent_item::type and SKINNY_METADATA feature.

- key->offset alignment check for EXTENT_ITEM

- key->offset check for METADATA_ITEM

- item size check
  Both against minimal size and stepping check.

- btrfs_extent_item check
  Checks its flags and generation.

- btrfs_extent_inline_ref checks
  Against 4 types inline ref.
  Checks bytenr alignment and tree level.

- btrfs_extent_item::refs check
  Check against total refs found in inline refs.

This check would be the most complex single item check due to its nature
of inlined items.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/tree-checker.c

@@ -910,6 +910,250 @@ static int check_root_item(struct extent_buffer *leaf, struct btrfs_key *key,
 	return 0;
 }
 
+__printf(3,4)
+__cold
+static void extent_err(const struct extent_buffer *eb, int slot,
+		       const char *fmt, ...)
+{
+	struct btrfs_key key;
+	struct va_format vaf;
+	va_list args;
+	u64 bytenr;
+	u64 len;
+
+	btrfs_item_key_to_cpu(eb, &key, slot);
+	bytenr = key.objectid;
+	if (key.type == BTRFS_METADATA_ITEM_KEY)
+		len = eb->fs_info->nodesize;
+	else
+		len = key.offset;
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	btrfs_crit(eb->fs_info,
+	"corrupt %s: block=%llu slot=%d extent bytenr=%llu len=%llu %pV",
+		btrfs_header_level(eb) == 0 ? "leaf" : "node",
+		eb->start, slot, bytenr, len, &vaf);
+	va_end(args);
+}
+
+static int check_extent_item(struct extent_buffer *leaf,
+			     struct btrfs_key *key, int slot)
+{
+	struct btrfs_fs_info *fs_info = leaf->fs_info;
+	struct btrfs_extent_item *ei;
+	bool is_tree_block = false;
+	unsigned long ptr;	/* Current pointer inside inline refs */
+	unsigned long end;	/* Extent item end */
+	const u32 item_size = btrfs_item_size_nr(leaf, slot);
+	u64 flags;
+	u64 generation;
+	u64 total_refs;		/* Total refs in btrfs_extent_item */
+	u64 inline_refs = 0;	/* found total inline refs */
+
+	if (key->type == BTRFS_METADATA_ITEM_KEY &&
+	    !btrfs_fs_incompat(fs_info, SKINNY_METADATA)) {
+		generic_err(leaf, slot,
+"invalid key type, METADATA_ITEM type invalid when SKINNY_METADATA feature disabled");
+		return -EUCLEAN;
+	}
+	/* key->objectid is the bytenr for both key types */
+	if (!IS_ALIGNED(key->objectid, fs_info->sectorsize)) {
+		generic_err(leaf, slot,
+		"invalid key objectid, have %llu expect to be aligned to %u",
+			   key->objectid, fs_info->sectorsize);
+		return -EUCLEAN;
+	}
+
+	/* key->offset is tree level for METADATA_ITEM_KEY */
+	if (key->type == BTRFS_METADATA_ITEM_KEY &&
+	    key->offset >= BTRFS_MAX_LEVEL) {
+		extent_err(leaf, slot,
+			   "invalid tree level, have %llu expect [0, %u]",
+			   key->offset, BTRFS_MAX_LEVEL - 1);
+		return -EUCLEAN;
+	}
+
+	/*
+	 * EXTENT/METADATA_ITEM consists of:
+	 * 1) One btrfs_extent_item
+	 *    Records the total refs, type and generation of the extent.
+	 *
+	 * 2) One btrfs_tree_block_info (for EXTENT_ITEM and tree backref only)
+	 *    Records the first key and level of the tree block.
+	 *
+	 * 2) Zero or more btrfs_extent_inline_ref(s)
+	 *    Each inline ref has one btrfs_extent_inline_ref shows:
+	 *    2.1) The ref type, one of the 4
+	 *         TREE_BLOCK_REF	Tree block only
+	 *         SHARED_BLOCK_REF	Tree block only
+	 *         EXTENT_DATA_REF	Data only
+	 *         SHARED_DATA_REF	Data only
+	 *    2.2) Ref type specific data
+	 *         Either using btrfs_extent_inline_ref::offset, or specific
+	 *         data structure.
+	 */
+	if (item_size < sizeof(*ei)) {
+		extent_err(leaf, slot,
+			   "invalid item size, have %u expect [%zu, %u)",
+			   item_size, sizeof(*ei),
+			   BTRFS_LEAF_DATA_SIZE(fs_info));
+		return -EUCLEAN;
+	}
+	end = item_size + btrfs_item_ptr_offset(leaf, slot);
+
+	/* Checks against extent_item */
+	ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
+	flags = btrfs_extent_flags(leaf, ei);
+	total_refs = btrfs_extent_refs(leaf, ei);
+	generation = btrfs_extent_generation(leaf, ei);
+	if (generation > btrfs_super_generation(fs_info->super_copy) + 1) {
+		extent_err(leaf, slot,
+			   "invalid generation, have %llu expect (0, %llu]",
+			   generation,
+			   btrfs_super_generation(fs_info->super_copy) + 1);
+		return -EUCLEAN;
+	}
+	if (!is_power_of_2(flags & (BTRFS_EXTENT_FLAG_DATA |
+				    BTRFS_EXTENT_FLAG_TREE_BLOCK))) {
+		extent_err(leaf, slot,
+		"invalid extent flag, have 0x%llx expect 1 bit set in 0x%llx",
+			flags, BTRFS_EXTENT_FLAG_DATA |
+			BTRFS_EXTENT_FLAG_TREE_BLOCK);
+		return -EUCLEAN;
+	}
+	is_tree_block = !!(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK);
+	if (is_tree_block) {
+		if (key->type == BTRFS_EXTENT_ITEM_KEY &&
+		    key->offset != fs_info->nodesize) {
+			extent_err(leaf, slot,
+				   "invalid extent length, have %llu expect %u",
+				   key->offset, fs_info->nodesize);
+			return -EUCLEAN;
+		}
+	} else {
+		if (key->type != BTRFS_EXTENT_ITEM_KEY) {
+			extent_err(leaf, slot,
+			"invalid key type, have %u expect %u for data backref",
+				   key->type, BTRFS_EXTENT_ITEM_KEY);
+			return -EUCLEAN;
+		}
+		if (!IS_ALIGNED(key->offset, fs_info->sectorsize)) {
+			extent_err(leaf, slot,
+			"invalid extent length, have %llu expect aligned to %u",
+				   key->offset, fs_info->sectorsize);
+			return -EUCLEAN;
+		}
+	}
+	ptr = (unsigned long)(struct btrfs_extent_item *)(ei + 1);
+
+	/* Check the special case of btrfs_tree_block_info */
+	if (is_tree_block && key->type != BTRFS_METADATA_ITEM_KEY) {
+		struct btrfs_tree_block_info *info;
+
+		info = (struct btrfs_tree_block_info *)ptr;
+		if (btrfs_tree_block_level(leaf, info) >= BTRFS_MAX_LEVEL) {
+			extent_err(leaf, slot,
+			"invalid tree block info level, have %u expect [0, %u]",
+				   btrfs_tree_block_level(leaf, info),
+				   BTRFS_MAX_LEVEL - 1);
+			return -EUCLEAN;
+		}
+		ptr = (unsigned long)(struct btrfs_tree_block_info *)(info + 1);
+	}
+
+	/* Check inline refs */
+	while (ptr < end) {
+		struct btrfs_extent_inline_ref *iref;
+		struct btrfs_extent_data_ref *dref;
+		struct btrfs_shared_data_ref *sref;
+		u64 dref_offset;
+		u64 inline_offset;
+		u8 inline_type;
+
+		if (ptr + sizeof(*iref) > end) {
+			extent_err(leaf, slot,
+"inline ref item overflows extent item, ptr %lu iref size %zu end %lu",
+				   ptr, sizeof(*iref), end);
+			return -EUCLEAN;
+		}
+		iref = (struct btrfs_extent_inline_ref *)ptr;
+		inline_type = btrfs_extent_inline_ref_type(leaf, iref);
+		inline_offset = btrfs_extent_inline_ref_offset(leaf, iref);
+		if (ptr + btrfs_extent_inline_ref_size(inline_type) > end) {
+			extent_err(leaf, slot,
+"inline ref item overflows extent item, ptr %lu iref size %u end %lu",
+				   ptr, inline_type, end);
+			return -EUCLEAN;
+		}
+
+		switch (inline_type) {
+		/* inline_offset is subvolid of the owner, no need to check */
+		case BTRFS_TREE_BLOCK_REF_KEY:
+			inline_refs++;
+			break;
+		/* Contains parent bytenr */
+		case BTRFS_SHARED_BLOCK_REF_KEY:
+			if (!IS_ALIGNED(inline_offset, fs_info->sectorsize)) {
+				extent_err(leaf, slot,
+		"invalid tree parent bytenr, have %llu expect aligned to %u",
+					   inline_offset, fs_info->sectorsize);
+				return -EUCLEAN;
+			}
+			inline_refs++;
+			break;
+		/*
+		 * Contains owner subvolid, owner key objectid, adjusted offset.
+		 * The only obvious corruption can happen in that offset.
+		 */
+		case BTRFS_EXTENT_DATA_REF_KEY:
+			dref = (struct btrfs_extent_data_ref *)(&iref->offset);
+			dref_offset = btrfs_extent_data_ref_offset(leaf, dref);
+			if (!IS_ALIGNED(dref_offset, fs_info->sectorsize)) {
+				extent_err(leaf, slot,
+		"invalid data ref offset, have %llu expect aligned to %u",
+					   dref_offset, fs_info->sectorsize);
+				return -EUCLEAN;
+			}
+			inline_refs += btrfs_extent_data_ref_count(leaf, dref);
+			break;
+		/* Contains parent bytenr and ref count */
+		case BTRFS_SHARED_DATA_REF_KEY:
+			sref = (struct btrfs_shared_data_ref *)(iref + 1);
+			if (!IS_ALIGNED(inline_offset, fs_info->sectorsize)) {
+				extent_err(leaf, slot,
+		"invalid data parent bytenr, have %llu expect aligned to %u",
+					   inline_offset, fs_info->sectorsize);
+				return -EUCLEAN;
+			}
+			inline_refs += btrfs_shared_data_ref_count(leaf, sref);
+			break;
+		default:
+			extent_err(leaf, slot, "unknown inline ref type: %u",
+				   inline_type);
+			return -EUCLEAN;
+		}
+		ptr += btrfs_extent_inline_ref_size(inline_type);
+	}
+	/* No padding is allowed */
+	if (ptr != end) {
+		extent_err(leaf, slot,
+			   "invalid extent item size, padding bytes found");
+		return -EUCLEAN;
+	}
+
+	/* Finally, check the inline refs against total refs */
+	if (inline_refs > total_refs) {
+		extent_err(leaf, slot,
+			"invalid extent refs, have %llu expect >= inline %llu",
+			   total_refs, inline_refs);
+		return -EUCLEAN;
+	}
+	return 0;
+}
+
 /*
  * Common point to switch the item-specific validation.
  */
@@ -948,6 +1192,10 @@ static int check_leaf_item(struct extent_buffer *leaf,
 	case BTRFS_ROOT_ITEM_KEY:
 		ret = check_root_item(leaf, key, slot);
 		break;
+	case BTRFS_EXTENT_ITEM_KEY:
+	case BTRFS_METADATA_ITEM_KEY:
+		ret = check_extent_item(leaf, key, slot);
+		break;
 	}
 	return ret;
 }