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 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);
129 out:
130 folio_end_read(folio, err == 0);
131 return err;
132 }
133
134 static 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 */
164 const struct address_space_operations udf_symlink_aops = {
165 .read_folio = udf_symlink_filler,
166 };
167
168 const struct inode_operations udf_symlink_inode_operations = {
169 .get_link = page_get_link,
170 .getattr = udf_symlink_getattr,
171 };
172
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