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; 39 __le32 disk_id; 40 int err; 41 42 if (index >= msblk->ids) 43 return -EINVAL; 44 45 start_block = le64_to_cpu(msblk->id_table[block]); 46 47 err = squashfs_read_metadata(sb, &disk_id, &start_block, &offset, 48 sizeof(disk_id)); 49 if (err < 0) 50 return err; 51 52 *id = le32_to_cpu(disk_id); 53 return 0; 54 } 55 56 57 /* 58 * Read uncompressed id lookup table indexes from disk into memory 59 */ 60 __le64 *squashfs_read_id_index_table(struct super_block *sb, 61 u64 id_table_start, u64 next_table, unsigned short no_ids) 62 { 63 unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids); 64 unsigned int indexes = SQUASHFS_ID_BLOCKS(no_ids); 65 int n; 66 __le64 *table; 67 u64 start, end; 68 69 TRACE("In read_id_index_table, length %d\n", length); 70 71 /* Sanity check values */ 72 73 /* there should always be at least one id */ 74 if (no_ids == 0) 75 return ERR_PTR(-EINVAL); 76 77 /* 78 * The computed size of the index table (length bytes) should exactly 79 * match the table start and end points 80 */ 81 if (length != (next_table - id_table_start)) 82 return ERR_PTR(-EINVAL); 83 84 table = squashfs_read_table(sb, id_table_start, length); 85 if (IS_ERR(table)) 86 return table; 87 88 /* 89 * table[0], table[1], ... table[indexes - 1] store the locations 90 * of the compressed id blocks. Each entry should be less than 91 * the next (i.e. table[0] < table[1]), and the difference between them 92 * should be SQUASHFS_METADATA_SIZE or less. table[indexes - 1] 93 * should be less than id_table_start, and again the difference 94 * should be SQUASHFS_METADATA_SIZE or less 95 */ 96 for (n = 0; n < (indexes - 1); n++) { 97 start = le64_to_cpu(table[n]); 98 end = le64_to_cpu(table[n + 1]); 99 100 if (start >= end || (end - start) > 101 (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) { 102 kfree(table); 103 return ERR_PTR(-EINVAL); 104 } 105 } 106 107 start = le64_to_cpu(table[indexes - 1]); 108 if (start >= id_table_start || (id_table_start - start) > 109 (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) { 110 kfree(table); 111 return ERR_PTR(-EINVAL); 112 } 113 114 return table; 115 } 116