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 pc = (struct pathComponent *)(from + elen); 40 elen += sizeof(struct pathComponent); 41 switch (pc->componentType) { 42 case 1: 43 /* 44 * Symlink points to some place which should be agreed 45 * upon between originator and receiver of the media. Ignore. 46 */ 47 if (pc->lengthComponentIdent > 0) { 48 elen += pc->lengthComponentIdent; 49 break; 50 } 51 fallthrough; 52 case 2: 53 if (tolen == 0) 54 return -ENAMETOOLONG; 55 p = to; 56 *p++ = '/'; 57 tolen--; 58 break; 59 case 3: 60 if (tolen < 3) 61 return -ENAMETOOLONG; 62 memcpy(p, "../", 3); 63 p += 3; 64 tolen -= 3; 65 break; 66 case 4: 67 if (tolen < 2) 68 return -ENAMETOOLONG; 69 memcpy(p, "./", 2); 70 p += 2; 71 tolen -= 2; 72 /* that would be . - just ignore */ 73 break; 74 case 5: 75 elen += pc->lengthComponentIdent; 76 if (elen > fromlen) 77 return -EIO; 78 comp_len = udf_get_filename(sb, pc->componentIdent, 79 pc->lengthComponentIdent, 80 p, tolen); 81 if (comp_len < 0) 82 return comp_len; 83 84 p += comp_len; 85 tolen -= comp_len; 86 if (tolen == 0) 87 return -ENAMETOOLONG; 88 *p++ = '/'; 89 tolen--; 90 break; 91 } 92 } 93 if (p > to + 1) 94 p[-1] = '\0'; 95 else 96 p[0] = '\0'; 97 return 0; 98 } 99 100 static int udf_symlink_filler(struct file *file, struct folio *folio) 101 { 102 struct page *page = &folio->page; 103 struct inode *inode = page->mapping->host; 104 struct buffer_head *bh = NULL; 105 unsigned char *symlink; 106 int err = 0; 107 unsigned char *p = page_address(page); 108 struct udf_inode_info *iinfo = UDF_I(inode); 109 110 /* We don't support symlinks longer than one block */ 111 if (inode->i_size > inode->i_sb->s_blocksize) { 112 err = -ENAMETOOLONG; 113 goto out_unlock; 114 } 115 116 if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) { 117 symlink = iinfo->i_data + iinfo->i_lenEAttr; 118 } else { 119 bh = udf_bread(inode, 0, 0, &err); 120 if (!bh) { 121 if (!err) 122 err = -EFSCORRUPTED; 123 goto out_err; 124 } 125 symlink = bh->b_data; 126 } 127 128 err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE); 129 brelse(bh); 130 if (err) 131 goto out_err; 132 133 SetPageUptodate(page); 134 unlock_page(page); 135 return 0; 136 137 out_err: 138 SetPageError(page); 139 out_unlock: 140 unlock_page(page); 141 return err; 142 } 143 144 static int udf_symlink_getattr(struct mnt_idmap *idmap, 145 const struct path *path, struct kstat *stat, 146 u32 request_mask, unsigned int flags) 147 { 148 struct dentry *dentry = path->dentry; 149 struct inode *inode = d_backing_inode(dentry); 150 struct page *page; 151 152 generic_fillattr(&nop_mnt_idmap, inode, stat); 153 page = read_mapping_page(inode->i_mapping, 0, NULL); 154 if (IS_ERR(page)) 155 return PTR_ERR(page); 156 /* 157 * UDF uses non-trivial encoding of symlinks so i_size does not match 158 * number of characters reported by readlink(2) which apparently some 159 * applications expect. Also POSIX says that "The value returned in the 160 * st_size field shall be the length of the contents of the symbolic 161 * link, and shall not count a trailing null if one is present." So 162 * let's report the length of string returned by readlink(2) for 163 * st_size. 164 */ 165 stat->size = strlen(page_address(page)); 166 put_page(page); 167 168 return 0; 169 } 170 171 /* 172 * symlinks can't do much... 173 */ 174 const struct address_space_operations udf_symlink_aops = { 175 .read_folio = udf_symlink_filler, 176 }; 177 178 const struct inode_operations udf_symlink_inode_operations = { 179 .get_link = page_get_link, 180 .getattr = udf_symlink_getattr, 181 }; 182