xattr_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) 2010
  6 * Phillip Lougher <phillip@squashfs.org.uk>
  7 *
  8 * xattr_id.c
  9 */
 10
 11/*
 12 * This file implements code to map the 32-bit xattr id stored in the inode
 13 * into the on disk location of the xattr data.
 14 */
 15
 16#include <linux/fs.h>
 17#include <linux/vfs.h>
 18#include <linux/slab.h>
 19
 20#include "squashfs_fs.h"
 21#include "squashfs_fs_sb.h"
 22#include "squashfs.h"
 23#include "xattr.h"
 24
 25/*
 26 * Map xattr id using the xattr id look up table
 27 */
 28int squashfs_xattr_lookup(struct super_block *sb, unsigned int index,
 29		int *count, unsigned int *size, unsigned long long *xattr)
 30{
 31	struct squashfs_sb_info *msblk = sb->s_fs_info;
 32	int block = SQUASHFS_XATTR_BLOCK(index);
 33	int offset = SQUASHFS_XATTR_BLOCK_OFFSET(index);
 34	u64 start_block;
 35	struct squashfs_xattr_id id;
 36	int err;
 37
 38	if (index >= msblk->xattr_ids)
 39		return -EINVAL;
 40
 41	start_block = le64_to_cpu(msblk->xattr_id_table[block]);
 42
 43	err = squashfs_read_metadata(sb, &id, &start_block, &offset,
 44							sizeof(id));
 45	if (err < 0)
 46		return err;
 47
 48	*xattr = le64_to_cpu(id.xattr);
 49	*size = le32_to_cpu(id.size);
 50	*count = le32_to_cpu(id.count);
 51	return 0;
 52}
 53
 54
 55/*
 56 * Read uncompressed xattr id lookup table indexes from disk into memory
 57 */
 58__le64 *squashfs_read_xattr_id_table(struct super_block *sb, u64 table_start,
 59		u64 *xattr_table_start, unsigned int *xattr_ids)
 60{
 61	struct squashfs_sb_info *msblk = sb->s_fs_info;
 62	unsigned int len, indexes;
 63	struct squashfs_xattr_id_table *id_table;
 64	__le64 *table;
 65	u64 start, end;
 66	int n;
 67
 68	id_table = squashfs_read_table(sb, table_start, sizeof(*id_table));
 69	if (IS_ERR(id_table))
 70		return (__le64 *) id_table;
 71
 72	*xattr_table_start = le64_to_cpu(id_table->xattr_table_start);
 73	*xattr_ids = le32_to_cpu(id_table->xattr_ids);
 74	kfree(id_table);
 75
 76	/* Sanity check values */
 77
 78	/* there is always at least one xattr id */
 79	if (*xattr_ids == 0)
 80		return ERR_PTR(-EINVAL);
 81
 82	len = SQUASHFS_XATTR_BLOCK_BYTES(*xattr_ids);
 83	indexes = SQUASHFS_XATTR_BLOCKS(*xattr_ids);
 84
 85	/*
 86	 * The computed size of the index table (len bytes) should exactly
 87	 * match the table start and end points
 88	 */
 89	start = table_start + sizeof(*id_table);
 90	end = msblk->bytes_used;
 91
 92	if (len != (end - start))
 93		return ERR_PTR(-EINVAL);
 94
 95	table = squashfs_read_table(sb, start, len);
 96	if (IS_ERR(table))
 97		return table;
 98
 99	/* table[0], table[1], ... table[indexes - 1] store the locations
100	 * of the compressed xattr id blocks.  Each entry should be less than
101	 * the next (i.e. table[0] < table[1]), and the difference between them
102	 * should be SQUASHFS_METADATA_SIZE or less.  table[indexes - 1]
103	 * should be less than table_start, and again the difference
104	 * shouls be SQUASHFS_METADATA_SIZE or less.
105	 *
106	 * Finally xattr_table_start should be less than table[0].
107	 */
108	for (n = 0; n < (indexes - 1); n++) {
109		start = le64_to_cpu(table[n]);
110		end = le64_to_cpu(table[n + 1]);
111
112		if (start >= end || (end - start) >
113				(SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
114			kfree(table);
115			return ERR_PTR(-EINVAL);
116		}
117	}
118
119	start = le64_to_cpu(table[indexes - 1]);
120	if (start >= table_start || (table_start - start) >
121				(SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {
122		kfree(table);
123		return ERR_PTR(-EINVAL);
124	}
125
126	if (*xattr_table_start >= le64_to_cpu(table[0])) {
127		kfree(table);
128		return ERR_PTR(-EINVAL);
129	}
130
131	return table;
132}