1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Squashfs - a compressed read only filesystem for Linux 4 * 5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 6 * Phillip Lougher <phillip@squashfs.org.uk> 7 * 8 * id.c 9 */ 10 11 /* 12 * This file implements code to handle uids and gids. 13 * 14 * For space efficiency regular files store uid and gid indexes, which are 15 * converted to 32-bit uids/gids using an id look up table. This table is 16 * stored compressed into metadata blocks. A second index table is used to 17 * locate these. This second index table for speed of access (and because it 18 * is small) is read at mount time and cached in memory. 19 */ 20 21 #include <linux/fs.h> 22 #include <linux/vfs.h> 23 #include <linux/slab.h> 24 25 #include "squashfs_fs.h" 26 #include "squashfs_fs_sb.h" 27 #include "squashfs.h" 28 29 /* 30 * Map uid/gid index into real 32-bit uid/gid using the id look up table 31 */ 32 int squashfs_get_id(struct super_block *sb, unsigned int index, 33 unsigned int *id) 34 { 35 struct squashfs_sb_info *msblk = sb->s_fs_info; 36 int block = SQUASHFS_ID_BLOCK(index); 37 int offset = SQUASHFS_ID_BLOCK_OFFSET(index); 38 u64 start_block = le64_to_cpu(msblk->id_table[block]); 39 __le32 disk_id; 40 int err; 41 42 err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset, 43 sizeof(disk_id)); 44 if (err < 0) 45 return err; 46 47 *id = le32_to_cpu(disk_id); 48 return 0; 49 } 50 51 52 /* 53 * Read uncompressed id lookup table indexes from disk into memory 54 */ 55 __le64 *squashfs_read_id_index_table(struct super_block *sb, 56 u64 id_table_start, u64 next_table, unsigned short no_ids) 57 { 58 unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids); 59 __le64 *table; 60 61 TRACE("In read_id_index_table, length %d\n", length); 62 63 /* Sanity check values */ 64 65 /* there should always be at least one id */ 66 if (no_ids == 0) 67 return ERR_PTR(-EINVAL); 68 69 /* 70 * length bytes should not extend into the next table - this check 71 * also traps instances where id_table_start is incorrectly larger 72 * than the next table start 73 */ 74 if (id_table_start + length > next_table) 75 return ERR_PTR(-EINVAL); 76 77 table = squashfs_read_table(sb, id_table_start, length); 78 79 /* 80 * table[0] points to the first id lookup table metadata block, this 81 * should be less than id_table_start 82 */ 83 if (!IS_ERR(table) && le64_to_cpu(table[0]) >= id_table_start) { 84 kfree(table); 85 return ERR_PTR(-EINVAL); 86 } 87 88 return table; 89 } 90