xref: /openbmc/linux/fs/squashfs/id.c (revision 5b448065)
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