fs/squashfs/id.c

   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 }