1 /* 2 * Squashfs - a compressed read only filesystem for Linux 3 * 4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 5 * Phillip Lougher <phillip@squashfs.org.uk> 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * as published by the Free Software Foundation; either version 2, 10 * or (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. 20 * 21 * id.c 22 */ 23 24 /* 25 * This file implements code to handle uids and gids. 26 * 27 * For space efficiency regular files store uid and gid indexes, which are 28 * converted to 32-bit uids/gids using an id look up table. This table is 29 * stored compressed into metadata blocks. A second index table is used to 30 * locate these. This second index table for speed of access (and because it 31 * is small) is read at mount time and cached in memory. 32 */ 33 34 #include <linux/fs.h> 35 #include <linux/vfs.h> 36 #include <linux/slab.h> 37 38 #include "squashfs_fs.h" 39 #include "squashfs_fs_sb.h" 40 #include "squashfs.h" 41 42 /* 43 * Map uid/gid index into real 32-bit uid/gid using the id look up table 44 */ 45 int squashfs_get_id(struct super_block *sb, unsigned int index, 46 unsigned int *id) 47 { 48 struct squashfs_sb_info *msblk = sb->s_fs_info; 49 int block = SQUASHFS_ID_BLOCK(index); 50 int offset = SQUASHFS_ID_BLOCK_OFFSET(index); 51 u64 start_block = le64_to_cpu(msblk->id_table[block]); 52 __le32 disk_id; 53 int err; 54 55 err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset, 56 sizeof(disk_id)); 57 if (err < 0) 58 return err; 59 60 *id = le32_to_cpu(disk_id); 61 return 0; 62 } 63 64 65 /* 66 * Read uncompressed id lookup table indexes from disk into memory 67 */ 68 __le64 *squashfs_read_id_index_table(struct super_block *sb, 69 u64 id_table_start, u64 next_table, unsigned short no_ids) 70 { 71 unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids); 72 __le64 *table; 73 74 TRACE("In read_id_index_table, length %d\n", length); 75 76 /* Sanity check values */ 77 78 /* there should always be at least one id */ 79 if (no_ids == 0) 80 return ERR_PTR(-EINVAL); 81 82 /* 83 * length bytes should not extend into the next table - this check 84 * also traps instances where id_table_start is incorrectly larger 85 * than the next table start 86 */ 87 if (id_table_start + length > next_table) 88 return ERR_PTR(-EINVAL); 89 90 table = squashfs_read_table(sb, id_table_start, length); 91 92 /* 93 * table[0] points to the first id lookup table metadata block, this 94 * should be less than id_table_start 95 */ 96 if (!IS_ERR(table) && le64_to_cpu(table[0]) >= id_table_start) { 97 kfree(table); 98 return ERR_PTR(-EINVAL); 99 } 100 101 return table; 102 } 103