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 = le64_to_cpu(msblk->inode_lookup_table[blk]); 45 __le64 ino; 46 int err; 47 48 TRACE("Entered squashfs_inode_lookup, inode_number = %d\n", ino_num); 49 50 err = squashfs_read_metadata(sb, &ino, &start, &offset, sizeof(ino)); 51 if (err < 0) 52 return err; 53 54 TRACE("squashfs_inode_lookup, inode = 0x%llx\n", 55 (u64) le64_to_cpu(ino)); 56 57 return le64_to_cpu(ino); 58 } 59 60 61 static struct dentry *squashfs_export_iget(struct super_block *sb, 62 unsigned int ino_num) 63 { 64 long long ino; 65 struct dentry *dentry = ERR_PTR(-ENOENT); 66 67 TRACE("Entered squashfs_export_iget\n"); 68 69 ino = squashfs_inode_lookup(sb, ino_num); 70 if (ino >= 0) 71 dentry = d_obtain_alias(squashfs_iget(sb, ino, ino_num)); 72 73 return dentry; 74 } 75 76 77 static struct dentry *squashfs_fh_to_dentry(struct super_block *sb, 78 struct fid *fid, int fh_len, int fh_type) 79 { 80 if ((fh_type != FILEID_INO32_GEN && fh_type != FILEID_INO32_GEN_PARENT) 81 || fh_len < 2) 82 return NULL; 83 84 return squashfs_export_iget(sb, fid->i32.ino); 85 } 86 87 88 static struct dentry *squashfs_fh_to_parent(struct super_block *sb, 89 struct fid *fid, int fh_len, int fh_type) 90 { 91 if (fh_type != FILEID_INO32_GEN_PARENT || fh_len < 4) 92 return NULL; 93 94 return squashfs_export_iget(sb, fid->i32.parent_ino); 95 } 96 97 98 static struct dentry *squashfs_get_parent(struct dentry *child) 99 { 100 struct inode *inode = d_inode(child); 101 unsigned int parent_ino = squashfs_i(inode)->parent; 102 103 return squashfs_export_iget(inode->i_sb, parent_ino); 104 } 105 106 107 /* 108 * Read uncompressed inode lookup table indexes off disk into memory 109 */ 110 __le64 *squashfs_read_inode_lookup_table(struct super_block *sb, 111 u64 lookup_table_start, u64 next_table, unsigned int inodes) 112 { 113 unsigned int length = SQUASHFS_LOOKUP_BLOCK_BYTES(inodes); 114 __le64 *table; 115 116 TRACE("In read_inode_lookup_table, length %d\n", length); 117 118 /* Sanity check values */ 119 120 /* there should always be at least one inode */ 121 if (inodes == 0) 122 return ERR_PTR(-EINVAL); 123 124 /* length bytes should not extend into the next table - this check 125 * also traps instances where lookup_table_start is incorrectly larger 126 * than the next table start 127 */ 128 if (lookup_table_start + length > next_table) 129 return ERR_PTR(-EINVAL); 130 131 table = squashfs_read_table(sb, lookup_table_start, length); 132 133 /* 134 * table[0] points to the first inode lookup table metadata block, 135 * this should be less than lookup_table_start 136 */ 137 if (!IS_ERR(table) && le64_to_cpu(table[0]) >= lookup_table_start) { 138 kfree(table); 139 return ERR_PTR(-EINVAL); 140 } 141 142 return table; 143 } 144 145 146 const struct export_operations squashfs_export_ops = { 147 .fh_to_dentry = squashfs_fh_to_dentry, 148 .fh_to_parent = squashfs_fh_to_parent, 149 .get_parent = squashfs_get_parent 150 }; 151