fs/btrfs/tree-checker.c

/*
 * Copyright (C) Qu Wenruo 2017.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program.
 */

/*
 * The module is used to catch unexpected/corrupted tree block data.
 * Such behavior can be caused either by a fuzzed image or bugs.
 *
 * The objective is to do leaf/node validation checks when tree block is read
 * from disk, and check *every* possible member, so other code won't
 * need to checking them again.
 *
 * Due to the potential and unwanted damage, every checker needs to be
 * carefully reviewed otherwise so it does not prevent mount of valid images.
 */

#include "ctree.h"
#include "tree-checker.h"
#include "disk-io.h"
#include "compression.h"

#define CORRUPT(reason, eb, root, slot)					\
	btrfs_crit(root->fs_info,					\
		   "corrupt %s, %s: block=%llu, root=%llu, slot=%d",	\
		   btrfs_header_level(eb) == 0 ? "leaf" : "node",	\
		   reason, btrfs_header_bytenr(eb), root->objectid, slot)

static int check_extent_data_item(struct btrfs_root *root,
				  struct extent_buffer *leaf,
				  struct btrfs_key *key, int slot)
{
	struct btrfs_file_extent_item *fi;
	u32 sectorsize = root->sectorsize;
	u32 item_size = btrfs_item_size_nr(leaf, slot);

	if (!IS_ALIGNED(key->offset, sectorsize)) {
		CORRUPT("unaligned key offset for file extent",
			leaf, root, slot);
		return -EUCLEAN;
	}

	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);

	if (btrfs_file_extent_type(leaf, fi) > BTRFS_FILE_EXTENT_TYPES) {
		CORRUPT("invalid file extent type", leaf, root, slot);
		return -EUCLEAN;
	}

	/*
	 * Support for new compression/encrption must introduce incompat flag,
	 * and must be caught in open_ctree().
	 */
	if (btrfs_file_extent_compression(leaf, fi) > BTRFS_COMPRESS_TYPES) {
		CORRUPT("invalid file extent compression", leaf, root, slot);
		return -EUCLEAN;
	}
	if (btrfs_file_extent_encryption(leaf, fi)) {
		CORRUPT("invalid file extent encryption", leaf, root, slot);
		return -EUCLEAN;
	}
	if (btrfs_file_extent_type(leaf, fi) == BTRFS_FILE_EXTENT_INLINE) {
		/* Inline extent must have 0 as key offset */
		if (key->offset) {
			CORRUPT("inline extent has non-zero key offset",
				leaf, root, slot);
			return -EUCLEAN;
		}

		/* Compressed inline extent has no on-disk size, skip it */
		if (btrfs_file_extent_compression(leaf, fi) !=
		    BTRFS_COMPRESS_NONE)
			return 0;

		/* Uncompressed inline extent size must match item size */
		if (item_size != BTRFS_FILE_EXTENT_INLINE_DATA_START +
		    btrfs_file_extent_ram_bytes(leaf, fi)) {
			CORRUPT("plaintext inline extent has invalid size",
				leaf, root, slot);
			return -EUCLEAN;
		}
		return 0;
	}

	/* Regular or preallocated extent has fixed item size */
	if (item_size != sizeof(*fi)) {
		CORRUPT(
		"regluar or preallocated extent data item size is invalid",
			leaf, root, slot);
		return -EUCLEAN;
	}
	if (!IS_ALIGNED(btrfs_file_extent_ram_bytes(leaf, fi), sectorsize) ||
	    !IS_ALIGNED(btrfs_file_extent_disk_bytenr(leaf, fi), sectorsize) ||
	    !IS_ALIGNED(btrfs_file_extent_disk_num_bytes(leaf, fi), sectorsize) ||
	    !IS_ALIGNED(btrfs_file_extent_offset(leaf, fi), sectorsize) ||
	    !IS_ALIGNED(btrfs_file_extent_num_bytes(leaf, fi), sectorsize)) {
		CORRUPT(
		"regular or preallocated extent data item has unaligned value",
			leaf, root, slot);
		return -EUCLEAN;
	}

	return 0;
}

static int check_csum_item(struct btrfs_root *root, struct extent_buffer *leaf,
			   struct btrfs_key *key, int slot)
{
	u32 sectorsize = root->sectorsize;
	u32 csumsize = btrfs_super_csum_size(root->fs_info->super_copy);

	if (key->objectid != BTRFS_EXTENT_CSUM_OBJECTID) {
		CORRUPT("invalid objectid for csum item", leaf, root, slot);
		return -EUCLEAN;
	}
	if (!IS_ALIGNED(key->offset, sectorsize)) {
		CORRUPT("unaligned key offset for csum item", leaf, root, slot);
		return -EUCLEAN;
	}
	if (!IS_ALIGNED(btrfs_item_size_nr(leaf, slot), csumsize)) {
		CORRUPT("unaligned csum item size", leaf, root, slot);
		return -EUCLEAN;
	}
	return 0;
}

/*
 * Common point to switch the item-specific validation.
 */
static int check_leaf_item(struct btrfs_root *root,
			   struct extent_buffer *leaf,
			   struct btrfs_key *key, int slot)
{
	int ret = 0;

	switch (key->type) {
	case BTRFS_EXTENT_DATA_KEY:
		ret = check_extent_data_item(root, leaf, key, slot);
		break;
	case BTRFS_EXTENT_CSUM_KEY:
		ret = check_csum_item(root, leaf, key, slot);
		break;
	}
	return ret;
}

int btrfs_check_leaf(struct btrfs_root *root, struct extent_buffer *leaf)
{
	struct btrfs_fs_info *fs_info = root->fs_info;
	/* No valid key type is 0, so all key should be larger than this key */
	struct btrfs_key prev_key = {0, 0, 0};
	struct btrfs_key key;
	u32 nritems = btrfs_header_nritems(leaf);
	int slot;

	/*
	 * Extent buffers from a relocation tree have a owner field that
	 * corresponds to the subvolume tree they are based on. So just from an
	 * extent buffer alone we can not find out what is the id of the
	 * corresponding subvolume tree, so we can not figure out if the extent
	 * buffer corresponds to the root of the relocation tree or not. So
	 * skip this check for relocation trees.
	 */
	if (nritems == 0 && !btrfs_header_flag(leaf, BTRFS_HEADER_FLAG_RELOC)) {
		struct btrfs_root *check_root;

		key.objectid = btrfs_header_owner(leaf);
		key.type = BTRFS_ROOT_ITEM_KEY;
		key.offset = (u64)-1;

		check_root = btrfs_get_fs_root(fs_info, &key, false);
		/*
		 * The only reason we also check NULL here is that during
		 * open_ctree() some roots has not yet been set up.
		 */
		if (!IS_ERR_OR_NULL(check_root)) {
			struct extent_buffer *eb;

			eb = btrfs_root_node(check_root);
			/* if leaf is the root, then it's fine */
			if (leaf != eb) {
				CORRUPT("non-root leaf's nritems is 0",
					leaf, check_root, 0);
				free_extent_buffer(eb);
				return -EUCLEAN;
			}
			free_extent_buffer(eb);
		}
		return 0;
	}

	if (nritems == 0)
		return 0;

	/*
	 * Check the following things to make sure this is a good leaf, and
	 * leaf users won't need to bother with similar sanity checks:
	 *
	 * 1) key ordering
	 * 2) item offset and size
	 *    No overlap, no hole, all inside the leaf.
	 * 3) item content
	 *    If possible, do comprehensive sanity check.
	 *    NOTE: All checks must only rely on the item data itself.
	 */
	for (slot = 0; slot < nritems; slot++) {
		u32 item_end_expected;
		int ret;

		btrfs_item_key_to_cpu(leaf, &key, slot);

		/* Make sure the keys are in the right order */
		if (btrfs_comp_cpu_keys(&prev_key, &key) >= 0) {
			CORRUPT("bad key order", leaf, root, slot);
			return -EUCLEAN;
		}

		/*
		 * Make sure the offset and ends are right, remember that the
		 * item data starts at the end of the leaf and grows towards the
		 * front.
		 */
		if (slot == 0)
			item_end_expected = BTRFS_LEAF_DATA_SIZE(root);
		else
			item_end_expected = btrfs_item_offset_nr(leaf,
								 slot - 1);
		if (btrfs_item_end_nr(leaf, slot) != item_end_expected) {
			CORRUPT("slot offset bad", leaf, root, slot);
			return -EUCLEAN;
		}

		/*
		 * Check to make sure that we don't point outside of the leaf,
		 * just in case all the items are consistent to each other, but
		 * all point outside of the leaf.
		 */
		if (btrfs_item_end_nr(leaf, slot) >
		    BTRFS_LEAF_DATA_SIZE(root)) {
			CORRUPT("slot end outside of leaf", leaf, root, slot);
			return -EUCLEAN;
		}

		/* Also check if the item pointer overlaps with btrfs item. */
		if (btrfs_item_nr_offset(slot) + sizeof(struct btrfs_item) >
		    btrfs_item_ptr_offset(leaf, slot)) {
			CORRUPT("slot overlap with its data", leaf, root, slot);
			return -EUCLEAN;
		}

		/* Check if the item size and content meet other criteria */
		ret = check_leaf_item(root, leaf, &key, slot);
		if (ret < 0)
			return ret;

		prev_key.objectid = key.objectid;
		prev_key.type = key.type;
		prev_key.offset = key.offset;
	}

	return 0;
}

int btrfs_check_node(struct btrfs_root *root, struct extent_buffer *node)
{
	unsigned long nr = btrfs_header_nritems(node);
	struct btrfs_key key, next_key;
	int slot;
	u64 bytenr;
	int ret = 0;

	if (nr == 0 || nr > BTRFS_NODEPTRS_PER_BLOCK(root)) {
		btrfs_crit(root->fs_info,
			   "corrupt node: block %llu root %llu nritems %lu",
			   node->start, root->objectid, nr);
		return -EIO;
	}

	for (slot = 0; slot < nr - 1; slot++) {
		bytenr = btrfs_node_blockptr(node, slot);
		btrfs_node_key_to_cpu(node, &key, slot);
		btrfs_node_key_to_cpu(node, &next_key, slot + 1);

		if (!bytenr) {
			CORRUPT("invalid item slot", node, root, slot);
			ret = -EIO;
			goto out;
		}

		if (btrfs_comp_cpu_keys(&key, &next_key) >= 0) {
			CORRUPT("bad key order", node, root, slot);
			ret = -EIO;
			goto out;
		}
	}
out:
	return ret;
}