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13#include <linux/fs.h>
14#include <linux/gfp.h>
15#include <linux/mount.h>
16#include <linux/module.h>
17#include <linux/kobject.h>
18#include <linux/namei.h>
19#include <linux/mutex.h>
20#include <linux/security.h>
21
22#include "sysfs.h"
23
24static int sysfs_do_create_link_sd(struct sysfs_dirent *parent_sd,
25 struct kobject *target,
26 const char *name, int warn)
27{
28 struct sysfs_dirent *target_sd = NULL;
29 struct sysfs_dirent *sd = NULL;
30 struct sysfs_addrm_cxt acxt;
31 enum kobj_ns_type ns_type;
32 int error;
33
34 BUG_ON(!name || !parent_sd);
35
36
37
38
39 spin_lock(&sysfs_assoc_lock);
40 if (target->sd)
41 target_sd = sysfs_get(target->sd);
42 spin_unlock(&sysfs_assoc_lock);
43
44 error = -ENOENT;
45 if (!target_sd)
46 goto out_put;
47
48 error = -ENOMEM;
49 sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
50 if (!sd)
51 goto out_put;
52
53 ns_type = sysfs_ns_type(parent_sd);
54 if (ns_type)
55 sd->s_ns = target->ktype->namespace(target);
56 sd->s_symlink.target_sd = target_sd;
57 target_sd = NULL;
58
59 sysfs_addrm_start(&acxt, parent_sd);
60
61 if (!ns_type ||
62 (ns_type == sysfs_ns_type(sd->s_symlink.target_sd->s_parent))) {
63 if (warn)
64 error = sysfs_add_one(&acxt, sd);
65 else
66 error = __sysfs_add_one(&acxt, sd);
67 } else {
68 error = -EINVAL;
69 WARN(1, KERN_WARNING
70 "sysfs: symlink across ns_types %s/%s -> %s/%s\n",
71 parent_sd->s_name,
72 sd->s_name,
73 sd->s_symlink.target_sd->s_parent->s_name,
74 sd->s_symlink.target_sd->s_name);
75 }
76 sysfs_addrm_finish(&acxt);
77
78 if (error)
79 goto out_put;
80
81 return 0;
82
83 out_put:
84 sysfs_put(target_sd);
85 sysfs_put(sd);
86 return error;
87}
88
89
90
91
92
93
94
95int sysfs_create_link_sd(struct sysfs_dirent *sd, struct kobject *target,
96 const char *name)
97{
98 return sysfs_do_create_link_sd(sd, target, name, 1);
99}
100
101static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
102 const char *name, int warn)
103{
104 struct sysfs_dirent *parent_sd = NULL;
105
106 if (!kobj)
107 parent_sd = &sysfs_root;
108 else
109 parent_sd = kobj->sd;
110
111 if (!parent_sd)
112 return -EFAULT;
113
114 return sysfs_do_create_link_sd(parent_sd, target, name, warn);
115}
116
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118
119
120
121
122
123int sysfs_create_link(struct kobject *kobj, struct kobject *target,
124 const char *name)
125{
126 return sysfs_do_create_link(kobj, target, name, 1);
127}
128EXPORT_SYMBOL_GPL(sysfs_create_link);
129
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137
138
139int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
140 const char *name)
141{
142 return sysfs_do_create_link(kobj, target, name, 0);
143}
144
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152
153
154void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
155 const char *name)
156{
157 const void *ns = NULL;
158 spin_lock(&sysfs_assoc_lock);
159 if (targ->sd && sysfs_ns_type(kobj->sd))
160 ns = targ->sd->s_ns;
161 spin_unlock(&sysfs_assoc_lock);
162 sysfs_hash_and_remove(kobj->sd, ns, name);
163}
164
165
166
167
168
169
170void sysfs_remove_link(struct kobject *kobj, const char *name)
171{
172 struct sysfs_dirent *parent_sd = NULL;
173
174 if (!kobj)
175 parent_sd = &sysfs_root;
176 else
177 parent_sd = kobj->sd;
178
179 sysfs_hash_and_remove(parent_sd, NULL, name);
180}
181EXPORT_SYMBOL_GPL(sysfs_remove_link);
182
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190
191
192int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
193 const char *old, const char *new)
194{
195 struct sysfs_dirent *parent_sd, *sd = NULL;
196 const void *old_ns = NULL, *new_ns = NULL;
197 int result;
198
199 if (!kobj)
200 parent_sd = &sysfs_root;
201 else
202 parent_sd = kobj->sd;
203
204 if (targ->sd)
205 old_ns = targ->sd->s_ns;
206
207 result = -ENOENT;
208 sd = sysfs_get_dirent(parent_sd, old_ns, old);
209 if (!sd)
210 goto out;
211
212 result = -EINVAL;
213 if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
214 goto out;
215 if (sd->s_symlink.target_sd->s_dir.kobj != targ)
216 goto out;
217
218 if (sysfs_ns_type(parent_sd))
219 new_ns = targ->ktype->namespace(targ);
220
221 result = sysfs_rename(sd, parent_sd, new_ns, new);
222
223out:
224 sysfs_put(sd);
225 return result;
226}
227EXPORT_SYMBOL_GPL(sysfs_rename_link);
228
229static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
230 struct sysfs_dirent *target_sd, char *path)
231{
232 struct sysfs_dirent *base, *sd;
233 char *s = path;
234 int len = 0;
235
236
237 base = parent_sd;
238 while (base->s_parent) {
239 sd = target_sd->s_parent;
240 while (sd->s_parent && base != sd)
241 sd = sd->s_parent;
242
243 if (base == sd)
244 break;
245
246 strcpy(s, "../");
247 s += 3;
248 base = base->s_parent;
249 }
250
251
252 sd = target_sd;
253 while (sd->s_parent && sd != base) {
254 len += strlen(sd->s_name) + 1;
255 sd = sd->s_parent;
256 }
257
258
259 if (len < 2)
260 return -EINVAL;
261 len--;
262 if ((s - path) + len > PATH_MAX)
263 return -ENAMETOOLONG;
264
265
266 sd = target_sd;
267 while (sd->s_parent && sd != base) {
268 int slen = strlen(sd->s_name);
269
270 len -= slen;
271 strncpy(s + len, sd->s_name, slen);
272 if (len)
273 s[--len] = '/';
274
275 sd = sd->s_parent;
276 }
277
278 return 0;
279}
280
281static int sysfs_getlink(struct dentry *dentry, char *path)
282{
283 struct sysfs_dirent *sd = dentry->d_fsdata;
284 struct sysfs_dirent *parent_sd = sd->s_parent;
285 struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
286 int error;
287
288 mutex_lock(&sysfs_mutex);
289 error = sysfs_get_target_path(parent_sd, target_sd, path);
290 mutex_unlock(&sysfs_mutex);
291
292 return error;
293}
294
295static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
296{
297 int error = -ENOMEM;
298 unsigned long page = get_zeroed_page(GFP_KERNEL);
299 if (page) {
300 error = sysfs_getlink(dentry, (char *) page);
301 if (error < 0)
302 free_page((unsigned long)page);
303 }
304 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
305 return NULL;
306}
307
308static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd,
309 void *cookie)
310{
311 char *page = nd_get_link(nd);
312 if (!IS_ERR(page))
313 free_page((unsigned long)page);
314}
315
316const struct inode_operations sysfs_symlink_inode_operations = {
317 .setxattr = sysfs_setxattr,
318 .readlink = generic_readlink,
319 .follow_link = sysfs_follow_link,
320 .put_link = sysfs_put_link,
321 .setattr = sysfs_setattr,
322 .getattr = sysfs_getattr,
323 .permission = sysfs_permission,
324};
325