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 * export.c 9 */ 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 in 15 * filehandles to an inode location on disk. This table is stored compressed 16 * into metadata blocks. A second index table is used to locate these. This 17 * second index table for speed of access (and because it is small) is read at 18 * mount time and cached in memory. 19 * 20 * The inode lookup table is used only by the export code, inode disk 21 * locations are directly encoded in directories, enabling direct access 22 * 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 */ 39 static 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 66 static 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 82 static 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 93 static 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 } 101 102 103 static 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 memory 114 */ 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 exactly 134 * match the table start and end points 135 */ 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 locations 145 * of the compressed inode lookup blocks. Each entry should be 146 * less than the next (i.e. table[0] < table[1]), and the difference 147 * between them should be SQUASHFS_METADATA_SIZE or less. 148 * table[indexes - 1] should be less than lookup_table_start, and 149 * again the difference should be SQUASHFS_METADATA_SIZE or less 150 */ 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 >= end 156 || (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 } 173 174 175 const 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_parent 180 }; 181