172 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2/*3 * symlink.c4 *5 * PURPOSE6 * Symlink handling routines for the OSTA-UDF(tm) filesystem.7 *8 * COPYRIGHT9 * (C) 1998-2001 Ben Fennema10 * (C) 1999 Stelias Computing Inc11 *12 * HISTORY13 *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 28static 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 agreed45 * 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 else96 p[0] = '\0';97 return 0;98}99 100static int udf_symlink_filler(struct file *file, struct folio *folio)101{102 struct inode *inode = folio->mapping->host;103 struct buffer_head *bh = NULL;104 unsigned char *symlink;105 int err = 0;106 unsigned char *p = folio_address(folio);107 struct udf_inode_info *iinfo = UDF_I(inode);108 109 /* We don't support symlinks longer than one block */110 if (inode->i_size > inode->i_sb->s_blocksize) {111 err = -ENAMETOOLONG;112 goto out;113 }114 115 if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {116 symlink = iinfo->i_data + iinfo->i_lenEAttr;117 } else {118 bh = udf_bread(inode, 0, 0, &err);119 if (!bh) {120 if (!err)121 err = -EFSCORRUPTED;122 goto out;123 }124 symlink = bh->b_data;125 }126 127 err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE);128 brelse(bh);129out:130 folio_end_read(folio, err == 0);131 return err;132}133 134static int udf_symlink_getattr(struct mnt_idmap *idmap,135 const struct path *path, struct kstat *stat,136 u32 request_mask, unsigned int flags)137{138 struct dentry *dentry = path->dentry;139 struct inode *inode = d_backing_inode(dentry);140 struct folio *folio;141 142 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);143 folio = read_mapping_folio(inode->i_mapping, 0, NULL);144 if (IS_ERR(folio))145 return PTR_ERR(folio);146 /*147 * UDF uses non-trivial encoding of symlinks so i_size does not match148 * number of characters reported by readlink(2) which apparently some149 * applications expect. Also POSIX says that "The value returned in the150 * st_size field shall be the length of the contents of the symbolic151 * link, and shall not count a trailing null if one is present." So152 * let's report the length of string returned by readlink(2) for153 * st_size.154 */155 stat->size = strlen(folio_address(folio));156 folio_put(folio);157 158 return 0;159}160 161/*162 * symlinks can't do much...163 */164const struct address_space_operations udf_symlink_aops = {165 .read_folio = udf_symlink_filler,166};167 168const struct inode_operations udf_symlink_inode_operations = {169 .get_link = page_get_link,170 .getattr = udf_symlink_getattr,171};172