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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
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 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
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 match
148 * number of characters reported by readlink(2) which apparently some
149 * applications expect. Also POSIX says that "The value returned in the
150 * st_size field shall be the length of the contents of the symbolic
151 * link, and shall not count a trailing null if one is present." So
152 * let's report the length of string returned by readlink(2) for
153 * 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};
1/*
2 * symlink.c
3 *
4 * PURPOSE
5 * Symlink handling routines for the OSTA-UDF(tm) filesystem.
6 *
7 * COPYRIGHT
8 * This file is distributed under the terms of the GNU General Public
9 * License (GPL). Copies of the GPL can be obtained from:
10 * ftp://prep.ai.mit.edu/pub/gnu/GPL
11 * Each contributing author retains all rights to their own work.
12 *
13 * (C) 1998-2001 Ben Fennema
14 * (C) 1999 Stelias Computing Inc
15 *
16 * HISTORY
17 *
18 * 04/16/99 blf Created.
19 *
20 */
21
22#include "udfdecl.h"
23#include <linux/uaccess.h>
24#include <linux/errno.h>
25#include <linux/fs.h>
26#include <linux/time.h>
27#include <linux/mm.h>
28#include <linux/stat.h>
29#include <linux/pagemap.h>
30#include "udf_i.h"
31
32static int udf_pc_to_char(struct super_block *sb, unsigned char *from,
33 int fromlen, unsigned char *to, int tolen)
34{
35 struct pathComponent *pc;
36 int elen = 0;
37 int comp_len;
38 unsigned char *p = to;
39
40 /* Reserve one byte for terminating \0 */
41 tolen--;
42 while (elen < fromlen) {
43 pc = (struct pathComponent *)(from + elen);
44 elen += sizeof(struct pathComponent);
45 switch (pc->componentType) {
46 case 1:
47 /*
48 * Symlink points to some place which should be agreed
49 * upon between originator and receiver of the media. Ignore.
50 */
51 if (pc->lengthComponentIdent > 0) {
52 elen += pc->lengthComponentIdent;
53 break;
54 }
55 fallthrough;
56 case 2:
57 if (tolen == 0)
58 return -ENAMETOOLONG;
59 p = to;
60 *p++ = '/';
61 tolen--;
62 break;
63 case 3:
64 if (tolen < 3)
65 return -ENAMETOOLONG;
66 memcpy(p, "../", 3);
67 p += 3;
68 tolen -= 3;
69 break;
70 case 4:
71 if (tolen < 2)
72 return -ENAMETOOLONG;
73 memcpy(p, "./", 2);
74 p += 2;
75 tolen -= 2;
76 /* that would be . - just ignore */
77 break;
78 case 5:
79 elen += pc->lengthComponentIdent;
80 if (elen > fromlen)
81 return -EIO;
82 comp_len = udf_get_filename(sb, pc->componentIdent,
83 pc->lengthComponentIdent,
84 p, tolen);
85 if (comp_len < 0)
86 return comp_len;
87
88 p += comp_len;
89 tolen -= comp_len;
90 if (tolen == 0)
91 return -ENAMETOOLONG;
92 *p++ = '/';
93 tolen--;
94 break;
95 }
96 }
97 if (p > to + 1)
98 p[-1] = '\0';
99 else
100 p[0] = '\0';
101 return 0;
102}
103
104static int udf_symlink_filler(struct file *file, struct folio *folio)
105{
106 struct page *page = &folio->page;
107 struct inode *inode = page->mapping->host;
108 struct buffer_head *bh = NULL;
109 unsigned char *symlink;
110 int err;
111 unsigned char *p = page_address(page);
112 struct udf_inode_info *iinfo;
113 uint32_t pos;
114
115 /* We don't support symlinks longer than one block */
116 if (inode->i_size > inode->i_sb->s_blocksize) {
117 err = -ENAMETOOLONG;
118 goto out_unmap;
119 }
120
121 iinfo = UDF_I(inode);
122 pos = udf_block_map(inode, 0);
123
124 down_read(&iinfo->i_data_sem);
125 if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
126 symlink = iinfo->i_data + iinfo->i_lenEAttr;
127 } else {
128 bh = sb_bread(inode->i_sb, pos);
129
130 if (!bh) {
131 err = -EIO;
132 goto out_unlock_inode;
133 }
134
135 symlink = bh->b_data;
136 }
137
138 err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE);
139 brelse(bh);
140 if (err)
141 goto out_unlock_inode;
142
143 up_read(&iinfo->i_data_sem);
144 SetPageUptodate(page);
145 unlock_page(page);
146 return 0;
147
148out_unlock_inode:
149 up_read(&iinfo->i_data_sem);
150 SetPageError(page);
151out_unmap:
152 unlock_page(page);
153 return err;
154}
155
156static int udf_symlink_getattr(struct user_namespace *mnt_userns,
157 const struct path *path, struct kstat *stat,
158 u32 request_mask, unsigned int flags)
159{
160 struct dentry *dentry = path->dentry;
161 struct inode *inode = d_backing_inode(dentry);
162 struct page *page;
163
164 generic_fillattr(&init_user_ns, inode, stat);
165 page = read_mapping_page(inode->i_mapping, 0, NULL);
166 if (IS_ERR(page))
167 return PTR_ERR(page);
168 /*
169 * UDF uses non-trivial encoding of symlinks so i_size does not match
170 * number of characters reported by readlink(2) which apparently some
171 * applications expect. Also POSIX says that "The value returned in the
172 * st_size field shall be the length of the contents of the symbolic
173 * link, and shall not count a trailing null if one is present." So
174 * let's report the length of string returned by readlink(2) for
175 * st_size.
176 */
177 stat->size = strlen(page_address(page));
178 put_page(page);
179
180 return 0;
181}
182
183/*
184 * symlinks can't do much...
185 */
186const struct address_space_operations udf_symlink_aops = {
187 .read_folio = udf_symlink_filler,
188};
189
190const struct inode_operations udf_symlink_inode_operations = {
191 .get_link = page_get_link,
192 .getattr = udf_symlink_getattr,
193};