blob: d38ea3dab95151916906bc1999d21b6cfa47f6a2 [file] [log] [blame]
* Squashfs - a compressed read only filesystem for Linux
* Phillip Lougher <>
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2,
* or (at your option) any later version.
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* id.c
* This file implements code to handle uids and gids.
* For space efficiency regular files store uid and gid indexes, which are
* converted to 32-bit uids/gids using an id look up table. This table is
* stored compressed into metadata blocks. A second index table is used to
* locate these. This second index table for speed of access (and because it
* is small) is read at mount time and cached in memory.
#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs.h"
* Map uid/gid index into real 32-bit uid/gid using the id look up table
int squashfs_get_id(struct super_block *sb, unsigned int index,
unsigned int *id)
struct squashfs_sb_info *msblk = sb->s_fs_info;
int block = SQUASHFS_ID_BLOCK(index);
int offset = SQUASHFS_ID_BLOCK_OFFSET(index);
u64 start_block = le64_to_cpu(msblk->id_table[block]);
__le32 disk_id;
int err;
err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset,
if (err < 0)
return err;
*id = le32_to_cpu(disk_id);
return 0;
* Read uncompressed id lookup table indexes from disk into memory
__le64 *squashfs_read_id_index_table(struct super_block *sb,
u64 id_table_start, u64 next_table, unsigned short no_ids)
unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
__le64 *table;
TRACE("In read_id_index_table, length %d\n", length);
/* Sanity check values */
/* there should always be at least one id */
if (no_ids == 0)
return ERR_PTR(-EINVAL);
* length bytes should not extend into the next table - this check
* also traps instances where id_table_start is incorrectly larger
* than the next table start
if (id_table_start + length > next_table)
return ERR_PTR(-EINVAL);
table = squashfs_read_table(sb, id_table_start, length);
* table[0] points to the first id lookup table metadata block, this
* should be less than id_table_start
if (!IS_ERR(table) && le64_to_cpu(table[0]) >= id_table_start) {
return ERR_PTR(-EINVAL);
return table;