lib/ext2fs/check_desc.c

/*
 * check_desc.c --- Check the group descriptors of an ext2 filesystem
 * 
 * Copyright (C) 1993, 1994 Theodore Ts'o.  This file may be redistributed
 * under the terms of the GNU Public License.
 */

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <time.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <linux/ext2_fs.h>

#include "ext2fs.h"

/*
 * This routine sanity checks the group descriptors
 */
errcode_t ext2fs_check_desc(ext2_filsys fs)
{
	int i;
	int block = fs->super->s_first_data_block;
	int next, inode_blocks_per_group;

	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

	inode_blocks_per_group = fs->super->s_inodes_per_group /
		EXT2_INODES_PER_BLOCK (fs->super);

	for (i = 0; i < fs->group_desc_count; i++) {
		next = block + fs->super->s_blocks_per_group;
		/*
		 * Check to make sure block bitmap for group is
		 * located within the group.
		 */
		if (fs->group_desc[i].bg_block_bitmap < block ||
		    fs->group_desc[i].bg_block_bitmap >= next)
			return EXT2_ET_GDESC_BAD_BLOCK_MAP;
		/*
		 * Check to make sure inode bitmap for group is
		 * located within the group
		 */
		if (fs->group_desc[i].bg_inode_bitmap < block ||
		    fs->group_desc[i].bg_inode_bitmap >= next)
			return EXT2_ET_GDESC_BAD_INODE_MAP;
		/*
		 * Check to make sure inode table for group is located
		 * within the group
		 */
		if (fs->group_desc[i].bg_inode_table < block ||
		    fs->group_desc[i].bg_inode_table+inode_blocks_per_group >=
		    next)
			return EXT2_ET_GDESC_BAD_INODE_TABLE;
		
		block = next;
	}
	return 0;
}