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;
  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 }