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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Tejun Heo6d66f5c2007-09-20 17:31:38 +09002 * fs/sysfs/symlink.c - sysfs symlink implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
7 *
8 * This file is released under the GPLv2.
9 *
10 * Please see Documentation/filesystems/sysfs.txt for more information.
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 */
12
13#include <linux/fs.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090014#include <linux/gfp.h>
Greg Kroah-Hartmanceeee1f2002-04-09 12:14:34 -070015#include <linux/mount.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070016#include <linux/module.h>
17#include <linux/kobject.h>
18#include <linux/namei.h>
Dave Young869512a2007-07-26 14:53:53 +000019#include <linux/mutex.h>
David P. Quigleyddd29ec2009-09-09 14:25:37 -040020#include <linux/security.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
22#include "sysfs.h"
23
Rafael J. Wysocki0bb8f3d2013-01-25 21:51:13 +010024static int sysfs_do_create_link_sd(struct sysfs_dirent *parent_sd,
25 struct kobject *target,
26 const char *name, int warn)
Linus Torvalds1da177e2005-04-16 15:20:36 -070027{
Tejun Heo2b29ac22007-06-14 03:45:15 +090028 struct sysfs_dirent *target_sd = NULL;
Tejun Heo3007e992007-06-14 04:27:23 +090029 struct sysfs_dirent *sd = NULL;
Tejun Heofb6896d2007-06-14 04:27:24 +090030 struct sysfs_addrm_cxt acxt;
Eric W. Biederman96d65232010-07-08 09:31:24 -070031 enum kobj_ns_type ns_type;
Tejun Heo3007e992007-06-14 04:27:23 +090032 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -070033
Rafael J. Wysocki0bb8f3d2013-01-25 21:51:13 +010034 BUG_ON(!name || !parent_sd);
Tejun Heo2b29ac22007-06-14 03:45:15 +090035
Tejun Heo608e2662007-06-14 04:27:22 +090036 /* target->sd can go away beneath us but is protected with
Tejun Heo5f995322007-06-14 04:27:23 +090037 * sysfs_assoc_lock. Fetch target_sd from it.
Tejun Heo2b29ac22007-06-14 03:45:15 +090038 */
Tejun Heo5f995322007-06-14 04:27:23 +090039 spin_lock(&sysfs_assoc_lock);
Tejun Heo608e2662007-06-14 04:27:22 +090040 if (target->sd)
41 target_sd = sysfs_get(target->sd);
Tejun Heo5f995322007-06-14 04:27:23 +090042 spin_unlock(&sysfs_assoc_lock);
Tejun Heo2b29ac22007-06-14 03:45:15 +090043
Tejun Heo3007e992007-06-14 04:27:23 +090044 error = -ENOENT;
Tejun Heo2b29ac22007-06-14 03:45:15 +090045 if (!target_sd)
Tejun Heo3007e992007-06-14 04:27:23 +090046 goto out_put;
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
Tejun Heo3007e992007-06-14 04:27:23 +090048 error = -ENOMEM;
49 sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
50 if (!sd)
51 goto out_put;
Tejun Heoa1da4df2007-07-18 16:14:45 +090052
Eric W. Biederman96d65232010-07-08 09:31:24 -070053 ns_type = sysfs_ns_type(parent_sd);
54 if (ns_type)
Eric W. Biederman3ff195b2010-03-30 11:31:26 -070055 sd->s_ns = target->ktype->namespace(target);
Tejun Heob1fc3d62007-09-20 16:05:11 +090056 sd->s_symlink.target_sd = target_sd;
Tejun Heoa1da4df2007-07-18 16:14:45 +090057 target_sd = NULL; /* reference is now owned by the symlink */
Tejun Heo2b29ac22007-06-14 03:45:15 +090058
Tejun Heofb6896d2007-06-14 04:27:24 +090059 sysfs_addrm_start(&acxt, parent_sd);
Eric W. Biederman96d65232010-07-08 09:31:24 -070060 /* Symlinks must be between directories with the same ns_type */
Eric W. Biedermand3300212010-07-20 22:12:01 -070061 if (!ns_type ||
62 (ns_type == sysfs_ns_type(sd->s_symlink.target_sd->s_parent))) {
Eric W. Biederman96d65232010-07-08 09:31:24 -070063 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 }
Tejun Heo23dc2792007-08-02 21:38:03 +090076 sysfs_addrm_finish(&acxt);
Tejun Heofb6896d2007-06-14 04:27:24 +090077
Tejun Heo23dc2792007-08-02 21:38:03 +090078 if (error)
Tejun Heo967e35d2007-07-18 16:38:11 +090079 goto out_put;
Tejun Heofb6896d2007-06-14 04:27:24 +090080
Tejun Heo967e35d2007-07-18 16:38:11 +090081 return 0;
82
Tejun Heo3007e992007-06-14 04:27:23 +090083 out_put:
84 sysfs_put(target_sd);
85 sysfs_put(sd);
Linus Torvalds1da177e2005-04-16 15:20:36 -070086 return error;
87}
88
Linus Torvalds1da177e2005-04-16 15:20:36 -070089/**
Rafael J. Wysocki0bb8f3d2013-01-25 21:51:13 +010090 * sysfs_create_link_sd - create symlink to a given object.
91 * @sd: directory we're creating the link in.
92 * @target: object we're pointing to.
93 * @name: name of the symlink.
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
117/**
Cornelia Huck36ce6da2008-06-10 11:09:08 +0200118 * sysfs_create_link - create symlink between two objects.
119 * @kobj: object whose directory we're creating the link in.
120 * @target: object we're pointing to.
121 * @name: name of the symlink.
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}
128
129/**
130 * sysfs_create_link_nowarn - create symlink between two objects.
131 * @kobj: object whose directory we're creating the link in.
132 * @target: object we're pointing to.
133 * @name: name of the symlink.
134 *
Robert P. J. Day6f1cbd42012-09-04 07:23:35 -0400135 * This function does the same as sysfs_create_link(), but it
Cornelia Huck36ce6da2008-06-10 11:09:08 +0200136 * doesn't warn if the link already exists.
137 */
138int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
139 const char *name)
140{
141 return sysfs_do_create_link(kobj, target, name, 0);
142}
143
144/**
Eric W. Biederman746edb72010-03-30 11:31:28 -0700145 * sysfs_delete_link - remove symlink in object's directory.
146 * @kobj: object we're acting for.
147 * @targ: object we're pointing to.
148 * @name: name of the symlink to remove.
149 *
150 * Unlike sysfs_remove_link sysfs_delete_link has enough information
151 * to successfully delete symlinks in tagged directories.
152 */
153void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
154 const char *name)
155{
156 const void *ns = NULL;
157 spin_lock(&sysfs_assoc_lock);
Eric W. Biederman521d0452010-07-20 22:10:58 -0700158 if (targ->sd && sysfs_ns_type(kobj->sd))
Eric W. Biederman746edb72010-03-30 11:31:28 -0700159 ns = targ->sd->s_ns;
160 spin_unlock(&sysfs_assoc_lock);
161 sysfs_hash_and_remove(kobj->sd, ns, name);
162}
163
164/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 * sysfs_remove_link - remove symlink in object's directory.
166 * @kobj: object we're acting for.
167 * @name: name of the symlink to remove.
168 */
169
Dmitry Torokhove3a15db2005-04-26 02:31:08 -0500170void sysfs_remove_link(struct kobject * kobj, const char * name)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171{
Mark Fasheha839c5a2008-01-29 14:35:18 -0800172 struct sysfs_dirent *parent_sd = NULL;
173
174 if (!kobj)
175 parent_sd = &sysfs_root;
176 else
177 parent_sd = kobj->sd;
178
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700179 sysfs_hash_and_remove(parent_sd, NULL, name);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180}
181
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800182/**
183 * sysfs_rename_link - rename symlink in object's directory.
184 * @kobj: object we're acting for.
185 * @targ: object we're pointing to.
186 * @old: previous name of the symlink.
187 * @new: new name of the symlink.
188 *
189 * A helper function for the common rename symlink idiom.
190 */
191int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
192 const char *old, const char *new)
193{
194 struct sysfs_dirent *parent_sd, *sd = NULL;
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700195 const void *old_ns = NULL, *new_ns = NULL;
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800196 int result;
197
198 if (!kobj)
199 parent_sd = &sysfs_root;
200 else
201 parent_sd = kobj->sd;
202
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700203 if (targ->sd)
204 old_ns = targ->sd->s_ns;
205
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800206 result = -ENOENT;
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700207 sd = sysfs_get_dirent(parent_sd, old_ns, old);
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800208 if (!sd)
209 goto out;
210
211 result = -EINVAL;
212 if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
213 goto out;
214 if (sd->s_symlink.target_sd->s_dir.kobj != targ)
215 goto out;
216
Eric W. Biederman3ff195b2010-03-30 11:31:26 -0700217 if (sysfs_ns_type(parent_sd))
218 new_ns = targ->ktype->namespace(targ);
219
220 result = sysfs_rename(sd, parent_sd, new_ns, new);
Eric W. Biederman7cb32942010-02-12 19:22:25 -0800221
222out:
223 sysfs_put(sd);
224 return result;
225}
226
Kay Sievers2f90a852007-11-01 20:20:52 +0100227static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
228 struct sysfs_dirent *target_sd, char *path)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229{
Kay Sievers2f90a852007-11-01 20:20:52 +0100230 struct sysfs_dirent *base, *sd;
231 char *s = path;
232 int len = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233
Kay Sievers2f90a852007-11-01 20:20:52 +0100234 /* go up to the root, stop at the base */
235 base = parent_sd;
236 while (base->s_parent) {
237 sd = target_sd->s_parent;
238 while (sd->s_parent && base != sd)
239 sd = sd->s_parent;
240
241 if (base == sd)
242 break;
243
244 strcpy(s, "../");
245 s += 3;
246 base = base->s_parent;
247 }
248
249 /* determine end of target string for reverse fillup */
250 sd = target_sd;
251 while (sd->s_parent && sd != base) {
252 len += strlen(sd->s_name) + 1;
253 sd = sd->s_parent;
254 }
255
256 /* check limits */
257 if (len < 2)
258 return -EINVAL;
259 len--;
260 if ((s - path) + len > PATH_MAX)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700261 return -ENAMETOOLONG;
262
Kay Sievers2f90a852007-11-01 20:20:52 +0100263 /* reverse fillup of target string from target to base */
264 sd = target_sd;
265 while (sd->s_parent && sd != base) {
266 int slen = strlen(sd->s_name);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267
Kay Sievers2f90a852007-11-01 20:20:52 +0100268 len -= slen;
269 strncpy(s + len, sd->s_name, slen);
270 if (len)
271 s[--len] = '/';
Linus Torvalds1da177e2005-04-16 15:20:36 -0700272
Kay Sievers2f90a852007-11-01 20:20:52 +0100273 sd = sd->s_parent;
274 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275
276 return 0;
277}
278
279static int sysfs_getlink(struct dentry *dentry, char * path)
280{
Tejun Heo2b29ac22007-06-14 03:45:15 +0900281 struct sysfs_dirent *sd = dentry->d_fsdata;
282 struct sysfs_dirent *parent_sd = sd->s_parent;
Tejun Heob1fc3d62007-09-20 16:05:11 +0900283 struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
Tejun Heo2b29ac22007-06-14 03:45:15 +0900284 int error;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285
Tejun Heo3007e992007-06-14 04:27:23 +0900286 mutex_lock(&sysfs_mutex);
Tejun Heo2b29ac22007-06-14 03:45:15 +0900287 error = sysfs_get_target_path(parent_sd, target_sd, path);
Tejun Heo3007e992007-06-14 04:27:23 +0900288 mutex_unlock(&sysfs_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289
Tejun Heo2b29ac22007-06-14 03:45:15 +0900290 return error;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291}
292
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700293static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294{
295 int error = -ENOMEM;
296 unsigned long page = get_zeroed_page(GFP_KERNEL);
Armin Kuster557411e2009-04-29 07:29:59 -1000297 if (page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298 error = sysfs_getlink(dentry, (char *) page);
Armin Kuster557411e2009-04-29 07:29:59 -1000299 if (error < 0)
300 free_page((unsigned long)page);
301 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700302 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700303 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304}
305
Linus Torvaldscc314ee2005-08-19 18:02:56 -0700306static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307{
308 char *page = nd_get_link(nd);
309 if (!IS_ERR(page))
310 free_page((unsigned long)page);
311}
312
Arjan van de Venc5ef1c42007-02-12 00:55:40 -0800313const struct inode_operations sysfs_symlink_inode_operations = {
Eric W. Biedermanc099aac2009-11-20 16:08:52 -0800314 .setxattr = sysfs_setxattr,
315 .readlink = generic_readlink,
316 .follow_link = sysfs_follow_link,
317 .put_link = sysfs_put_link,
Eric W. Biedermane61ab4a2009-11-20 16:08:53 -0800318 .setattr = sysfs_setattr,
319 .getattr = sysfs_getattr,
320 .permission = sysfs_permission,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700321};
322
323
324EXPORT_SYMBOL_GPL(sysfs_create_link);
325EXPORT_SYMBOL_GPL(sysfs_remove_link);
Simon Arlotte0f43752010-05-10 09:31:11 +0000326EXPORT_SYMBOL_GPL(sysfs_rename_link);