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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 * export.c9 */10 11/*12 * This file implements code to make Squashfs filesystems exportable (NFS etc.)13 *14 * The export code uses an inode lookup table to map inode numbers passed in15 * filehandles to an inode location on disk. This table is stored compressed16 * into metadata blocks. A second index table is used to locate these. This17 * second index table for speed of access (and because it is small) is read at18 * mount time and cached in memory.19 *20 * The inode lookup table is used only by the export code, inode disk21 * locations are directly encoded in directories, enabling direct access22 * without an intermediate lookup for all operations except the export ops.23 */24 25#include <linux/fs.h>26#include <linux/vfs.h>27#include <linux/dcache.h>28#include <linux/exportfs.h>29#include <linux/slab.h>30 31#include "squashfs_fs.h"32#include "squashfs_fs_sb.h"33#include "squashfs_fs_i.h"34#include "squashfs.h"35 36/*37 * Look-up inode number (ino) in table, returning the inode location.38 */39static long long squashfs_inode_lookup(struct super_block *sb, int ino_num)40{41 struct squashfs_sb_info *msblk = sb->s_fs_info;42 int blk = SQUASHFS_LOOKUP_BLOCK(ino_num - 1);43 int offset = SQUASHFS_LOOKUP_BLOCK_OFFSET(ino_num - 1);44 u64 start;45 __le64 ino;46 int err;47 48 TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num);49 50 if (ino_num == 0 || (ino_num - 1) >= msblk->inodes)51 return -EINVAL;52 53 start = le64_to_cpu(msblk->inode_lookup_table[blk]);54 55 err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino));56 if (err < 0)57 return err;58 59 TRACE("squashfs_inode_lookup, inode = 0x%llx\n",60 (u64) le64_to_cpu(ino));61 62 return le64_to_cpu(ino);63}64 65 66static struct dentry *squashfs_export_iget(struct super_block *sb,67 unsigned int ino_num)68{69 long long ino;70 struct dentry *dentry = ERR_PTR(-ENOENT);71 72 TRACE("Entered squashfs_export_iget\n");73 74 ino = squashfs_inode_lookup(sb, ino_num);75 if (ino >= 0)76 dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num));77 78 return dentry;79}80 81 82static struct dentry *squashfs_fh_to_dentry(struct super_block *sb,83 struct fid *fid, int fh_len, int fh_type)84{85 if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT)86 || fh_len < 2)87 return NULL;88 89 return squashfs_export_iget(sb, fid->i32.ino);90}91 92 93static struct dentry *squashfs_fh_to_parent(struct super_block *sb,94 struct fid *fid, int fh_len, int fh_type)95{96 if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4)97 return NULL;98 99 return squashfs_export_iget(sb, fid->i32.parent_ino);100}101 102 103static struct dentry *squashfs_get_parent(struct dentry *child)104{105 struct inode *inode = d_inode(child);106 unsigned int parent_ino = squashfs_i(inode)->parent;107 108 return squashfs_export_iget(inode->i_sb, parent_ino);109}110 111 112/*113 * Read uncompressed inode lookup table indexes off disk into memory114 */115__le64 *squashfs_read_inode_lookup_table(struct super_block *sb,116 u64 lookup_table_start, u64 next_table, unsigned int inodes)117{118 unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes);119 unsigned int indexes = SQUASHFS_LOOKUP_BLOCKS(inodes);120 int n;121 __le64 *table;122 u64 start, end;123 124 TRACE("In read_inode_lookup_table, length %d\n", length);125 126 /* Sanity check values */127 128 /* there should always be at least one inode */129 if (inodes == 0)130 return ERR_PTR(-EINVAL);131 132 /*133 * The computed size of the lookup table (length bytes) should exactly134 * match the table start and end points135 */136 if (length != (next_table - lookup_table_start))137 return ERR_PTR(-EINVAL);138 139 table = squashfs_read_table(sb, lookup_table_start, length);140 if (IS_ERR(table))141 return table;142 143 /*144 * table0], table[1], ... table[indexes - 1] store the locations145 * of the compressed inode lookup blocks. Each entry should be146 * less than the next (i.e. table[0] < table[1]), and the difference147 * between them should be SQUASHFS_METADATA_SIZE or less.148 * table[indexes - 1] should be less than lookup_table_start, and149 * again the difference should be SQUASHFS_METADATA_SIZE or less150 */151 for (n = 0; n < (indexes - 1); n++) {152 start = le64_to_cpu(table[n]);153 end = le64_to_cpu(table[n + 1]);154 155 if (start >= end156 || (end - start) >157 (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {158 kfree(table);159 return ERR_PTR(-EINVAL);160 }161 }162 163 start = le64_to_cpu(table[indexes - 1]);164 if (start >= lookup_table_start ||165 (lookup_table_start - start) >166 (SQUASHFS_METADATA_SIZE + SQUASHFS_BLOCK_OFFSET)) {167 kfree(table);168 return ERR_PTR(-EINVAL);169 }170 171 return table;172}173 174 175const struct export_operations squashfs_export_ops = {176 .encode_fh = generic_encode_ino32_fh,177 .fh_to_dentry = squashfs_fh_to_dentry,178 .fh_to_parent = squashfs_fh_to_parent,179 .get_parent = squashfs_get_parent180};181