1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * symlink.c 4 * 5 * PURPOSE 6 * Symlink handling routines for the OSTA-UDF(tm) filesystem. 7 * 8 * COPYRIGHT 9 * (C) 1998-2001 Ben Fennema 10 * (C) 1999 Stelias Computing Inc 11 * 12 * HISTORY 13 * 14 * 04/16/99 blf Created. 15 * 16 */ 17 18 #include "udfdecl.h" 19 #include <linux/uaccess.h> 20 #include <linux/errno.h> 21 #include <linux/fs.h> 22 #include <linux/time.h> 23 #include <linux/mm.h> 24 #include <linux/stat.h> 25 #include <linux/pagemap.h> 26 #include "udf_i.h" 27 28 static int udf_pc_to_char(struct super_block *sb, unsigned char *from, 29 int fromlen, unsigned char *to, int tolen) 30 { 31 struct pathComponent *pc; 32 int elen = 0; 33 int comp_len; 34 unsigned char *p = to; 35 36 /* Reserve one byte for terminating \0 */ 37 tolen--; 38 while (elen < fromlen) { 39 if (fromlen - elen < sizeof(struct pathComponent)) 40 return -EIO; 41 pc = (struct pathComponent *)(from + elen); 42 elen += sizeof(struct pathComponent); 43 switch (pc->componentType) { 44 case 1: 45 /* 46 * Symlink points to some place which should be agreed 47 * upon between originator and receiver of the media. Ignore. 48 */ 49 if (pc->lengthComponentIdent > 0) { 50 elen += pc->lengthComponentIdent; 51 break; 52 } 53 fallthrough; 54 case 2: 55 if (tolen == 0) 56 return -ENAMETOOLONG; 57 p = to; 58 *p++ = '/'; 59 tolen--; 60 break; 61 case 3: 62 if (tolen < 3) 63 return -ENAMETOOLONG; 64 memcpy(p, "../", 3); 65 p += 3; 66 tolen -= 3; 67 break; 68 case 4: 69 if (tolen < 2) 70 return -ENAMETOOLONG; 71 memcpy(p, "./", 2); 72 p += 2; 73 tolen -= 2; 74 /* that would be . - just ignore */ 75 break; 76 case 5: 77 elen += pc->lengthComponentIdent; 78 if (elen > fromlen) 79 return -EIO; 80 comp_len = udf_get_filename(sb, pc->componentIdent, 81 pc->lengthComponentIdent, 82 p, tolen); 83 if (comp_len < 0) 84 return comp_len; 85 86 p += comp_len; 87 tolen -= comp_len; 88 if (tolen == 0) 89 return -ENAMETOOLONG; 90 *p++ = '/'; 91 tolen--; 92 break; 93 } 94 } 95 if (p > to + 1) 96 p[-1] = '\0'; 97 else 98 p[0] = '\0'; 99 return 0; 100 } 101 102 static int udf_symlink_filler(struct file *file, struct folio *folio) 103 { 104 struct inode *inode = folio->mapping->host; 105 struct buffer_head *bh = NULL; 106 unsigned char *symlink; 107 int err = 0; 108 unsigned char *p = folio_address(folio); 109 struct udf_inode_info *iinfo = UDF_I(inode); 110 111 /* We don't support symlinks longer than one block */ 112 if (inode->i_size > inode->i_sb->s_blocksize) { 113 err = -ENAMETOOLONG; 114 goto out; 115 } 116 117 if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) { 118 symlink = iinfo->i_data + iinfo->i_lenEAttr; 119 } else { 120 bh = udf_bread(inode, 0, 0, &err); 121 if (!bh) { 122 if (!err) 123 err = -EFSCORRUPTED; 124 goto out; 125 } 126 symlink = bh->b_data; 127 } 128 129 err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE); 130 brelse(bh); 131 out: 132 folio_end_read(folio, err == 0); 133 return err; 134 } 135 136 static int udf_symlink_getattr(const struct mnt_idmap *idmap, 137 const struct path *path, struct kstat *stat, 138 u32 request_mask, unsigned int flags) 139 { 140 struct dentry *dentry = path->dentry; 141 struct inode *inode = d_backing_inode(dentry); 142 struct folio *folio; 143 144 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); 145 folio = read_mapping_folio(inode->i_mapping, 0, NULL); 146 if (IS_ERR(folio)) 147 return PTR_ERR(folio); 148 /* 149 * UDF uses non-trivial encoding of symlinks so i_size does not match 150 * number of characters reported by readlink(2) which apparently some 151 * applications expect. Also POSIX says that "The value returned in the 152 * st_size field shall be the length of the contents of the symbolic 153 * link, and shall not count a trailing null if one is present." So 154 * let's report the length of string returned by readlink(2) for 155 * st_size. 156 */ 157 stat->size = strlen(folio_address(folio)); 158 folio_put(folio); 159 160 return 0; 161 } 162 163 /* 164 * symlinks can't do much... 165 */ 166 const struct address_space_operations udf_symlink_aops = { 167 .read_folio = udf_symlink_filler, 168 }; 169 170 const struct inode_operations udf_symlink_inode_operations = { 171 .get_link = page_get_link, 172 .getattr = udf_symlink_getattr, 173 }; 174