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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Squashfs - a compressed read only filesystem for Linux4 *5 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 20086 * Phillip Lougher <phillip@squashfs.org.uk>7 *8 * id.c9 */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 are15 * converted to 32-bit uids/gids using an id look up table. This table is16 * stored compressed into metadata blocks. A second index table is used to17 * locate these. This second index table for speed of access (and because it18 * 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 table31 */32int 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 memory59 */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 exactly79 * match the table start and end points80 */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 locations90 * of the compressed id blocks. Each entry should be less than91 * the next (i.e. table[0] < table[1]), and the difference between them92 * should be SQUASHFS_METADATA_SIZE or less. table[indexes - 1]93 * should be less than id_table_start, and again the difference94 * should be SQUASHFS_METADATA_SIZE or less95 */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