Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * fs/sysfs/symlink.c - sysfs symlink implementation
4 : *
5 : * Copyright (c) 2001-3 Patrick Mochel
6 : * Copyright (c) 2007 SUSE Linux Products GmbH
7 : * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
8 : *
9 : * Please see Documentation/filesystems/sysfs.rst for more information.
10 : */
11 :
12 : #include <linux/fs.h>
13 : #include <linux/module.h>
14 : #include <linux/kobject.h>
15 : #include <linux/mutex.h>
16 : #include <linux/security.h>
17 :
18 : #include "sysfs.h"
19 :
20 1752 : static int sysfs_do_create_link_sd(struct kernfs_node *parent,
21 : struct kobject *target_kobj,
22 : const char *name, int warn)
23 : {
24 1752 : struct kernfs_node *kn, *target = NULL;
25 :
26 1752 : if (WARN_ON(!name || !parent))
27 : return -EINVAL;
28 :
29 : /*
30 : * We don't own @target_kobj and it may be removed at any time.
31 : * Synchronize using sysfs_symlink_target_lock. See
32 : * sysfs_remove_dir() for details.
33 : */
34 1752 : spin_lock(&sysfs_symlink_target_lock);
35 1752 : if (target_kobj->sd) {
36 1752 : target = target_kobj->sd;
37 1752 : kernfs_get(target);
38 : }
39 1752 : spin_unlock(&sysfs_symlink_target_lock);
40 :
41 1752 : if (!target)
42 : return -ENOENT;
43 :
44 1752 : kn = kernfs_create_link(parent, name, target);
45 1752 : kernfs_put(target);
46 :
47 1752 : if (!IS_ERR(kn))
48 : return 0;
49 :
50 0 : if (warn && PTR_ERR(kn) == -EEXIST)
51 0 : sysfs_warn_dup(parent, name);
52 0 : return PTR_ERR(kn);
53 : }
54 :
55 : /**
56 : * sysfs_create_link_sd - create symlink to a given object.
57 : * @kn: directory we're creating the link in.
58 : * @target: object we're pointing to.
59 : * @name: name of the symlink.
60 : */
61 0 : int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
62 : const char *name)
63 : {
64 0 : return sysfs_do_create_link_sd(kn, target, name, 1);
65 : }
66 :
67 : static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
68 : const char *name, int warn)
69 : {
70 1752 : struct kernfs_node *parent = NULL;
71 :
72 1752 : if (!kobj)
73 0 : parent = sysfs_root_kn;
74 : else
75 1752 : parent = kobj->sd;
76 :
77 1752 : if (!parent)
78 : return -EFAULT;
79 :
80 1752 : return sysfs_do_create_link_sd(parent, target, name, warn);
81 : }
82 :
83 : /**
84 : * sysfs_create_link - create symlink between two objects.
85 : * @kobj: object whose directory we're creating the link in.
86 : * @target: object we're pointing to.
87 : * @name: name of the symlink.
88 : */
89 1752 : int sysfs_create_link(struct kobject *kobj, struct kobject *target,
90 : const char *name)
91 : {
92 1752 : return sysfs_do_create_link(kobj, target, name, 1);
93 : }
94 : EXPORT_SYMBOL_GPL(sysfs_create_link);
95 :
96 : /**
97 : * sysfs_create_link_nowarn - create symlink between two objects.
98 : * @kobj: object whose directory we're creating the link in.
99 : * @target: object we're pointing to.
100 : * @name: name of the symlink.
101 : *
102 : * This function does the same as sysfs_create_link(), but it
103 : * doesn't warn if the link already exists.
104 : */
105 0 : int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
106 : const char *name)
107 : {
108 0 : return sysfs_do_create_link(kobj, target, name, 0);
109 : }
110 : EXPORT_SYMBOL_GPL(sysfs_create_link_nowarn);
111 :
112 : /**
113 : * sysfs_delete_link - remove symlink in object's directory.
114 : * @kobj: object we're acting for.
115 : * @targ: object we're pointing to.
116 : * @name: name of the symlink to remove.
117 : *
118 : * Unlike sysfs_remove_link sysfs_delete_link has enough information
119 : * to successfully delete symlinks in tagged directories.
120 : */
121 1 : void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
122 : const char *name)
123 : {
124 1 : const void *ns = NULL;
125 :
126 : /*
127 : * We don't own @target and it may be removed at any time.
128 : * Synchronize using sysfs_symlink_target_lock. See
129 : * sysfs_remove_dir() for details.
130 : */
131 1 : spin_lock(&sysfs_symlink_target_lock);
132 1 : if (targ->sd && kernfs_ns_enabled(kobj->sd))
133 0 : ns = targ->sd->ns;
134 1 : spin_unlock(&sysfs_symlink_target_lock);
135 1 : kernfs_remove_by_name_ns(kobj->sd, name, ns);
136 1 : }
137 :
138 : /**
139 : * sysfs_remove_link - remove symlink in object's directory.
140 : * @kobj: object we're acting for.
141 : * @name: name of the symlink to remove.
142 : */
143 177 : void sysfs_remove_link(struct kobject *kobj, const char *name)
144 : {
145 177 : struct kernfs_node *parent = NULL;
146 :
147 177 : if (!kobj)
148 0 : parent = sysfs_root_kn;
149 : else
150 177 : parent = kobj->sd;
151 :
152 177 : kernfs_remove_by_name(parent, name);
153 177 : }
154 : EXPORT_SYMBOL_GPL(sysfs_remove_link);
155 :
156 : /**
157 : * sysfs_rename_link_ns - rename symlink in object's directory.
158 : * @kobj: object we're acting for.
159 : * @targ: object we're pointing to.
160 : * @old: previous name of the symlink.
161 : * @new: new name of the symlink.
162 : * @new_ns: new namespace of the symlink.
163 : *
164 : * A helper function for the common rename symlink idiom.
165 : */
166 0 : int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
167 : const char *old, const char *new, const void *new_ns)
168 : {
169 0 : struct kernfs_node *parent, *kn = NULL;
170 0 : const void *old_ns = NULL;
171 : int result;
172 :
173 0 : if (!kobj)
174 0 : parent = sysfs_root_kn;
175 : else
176 0 : parent = kobj->sd;
177 :
178 0 : if (targ->sd)
179 0 : old_ns = targ->sd->ns;
180 :
181 0 : result = -ENOENT;
182 0 : kn = kernfs_find_and_get_ns(parent, old, old_ns);
183 0 : if (!kn)
184 : goto out;
185 :
186 0 : result = -EINVAL;
187 0 : if (kernfs_type(kn) != KERNFS_LINK)
188 : goto out;
189 0 : if (kn->symlink.target_kn->priv != targ)
190 : goto out;
191 :
192 0 : result = kernfs_rename_ns(kn, parent, new, new_ns);
193 :
194 : out:
195 0 : kernfs_put(kn);
196 0 : return result;
197 : }
198 : EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);
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