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 | static int sysfs_do_create_link_sd(struct kernfs_node *parent, |
21 | struct kobject *target_kobj, |
22 | const char *name, int warn) |
23 | { |
24 | struct kernfs_node *kn, *target = NULL; |
25 | |
26 | 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 | spin_lock(lock: &sysfs_symlink_target_lock); |
35 | if (target_kobj->sd) { |
36 | target = target_kobj->sd; |
37 | kernfs_get(kn: target); |
38 | } |
39 | spin_unlock(lock: &sysfs_symlink_target_lock); |
40 | |
41 | if (!target) |
42 | return -ENOENT; |
43 | |
44 | kn = kernfs_create_link(parent, name, target); |
45 | kernfs_put(kn: target); |
46 | |
47 | if (!IS_ERR(ptr: kn)) |
48 | return 0; |
49 | |
50 | if (warn && PTR_ERR(ptr: kn) == -EEXIST) |
51 | sysfs_warn_dup(parent, name); |
52 | return PTR_ERR(ptr: 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 | int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target, |
62 | const char *name) |
63 | { |
64 | return sysfs_do_create_link_sd(parent: kn, target_kobj: target, name, warn: 1); |
65 | } |
66 | |
67 | static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, |
68 | const char *name, int warn) |
69 | { |
70 | struct kernfs_node *parent = NULL; |
71 | |
72 | if (!kobj) |
73 | parent = sysfs_root_kn; |
74 | else |
75 | parent = kobj->sd; |
76 | |
77 | if (!parent) |
78 | return -EFAULT; |
79 | |
80 | return sysfs_do_create_link_sd(parent, target_kobj: 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 | int sysfs_create_link(struct kobject *kobj, struct kobject *target, |
90 | const char *name) |
91 | { |
92 | return sysfs_do_create_link(kobj, target, name, warn: 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 | int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target, |
106 | const char *name) |
107 | { |
108 | return sysfs_do_create_link(kobj, target, name, warn: 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 | void sysfs_delete_link(struct kobject *kobj, struct kobject *targ, |
122 | const char *name) |
123 | { |
124 | 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 | spin_lock(lock: &sysfs_symlink_target_lock); |
132 | if (targ->sd && kernfs_ns_enabled(kn: kobj->sd)) |
133 | ns = targ->sd->ns; |
134 | spin_unlock(lock: &sysfs_symlink_target_lock); |
135 | kernfs_remove_by_name_ns(parent: kobj->sd, name, ns); |
136 | } |
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 | void sysfs_remove_link(struct kobject *kobj, const char *name) |
144 | { |
145 | struct kernfs_node *parent = NULL; |
146 | |
147 | if (!kobj) |
148 | parent = sysfs_root_kn; |
149 | else |
150 | parent = kobj->sd; |
151 | |
152 | kernfs_remove_by_name(parent, name); |
153 | } |
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 | int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ, |
167 | const char *old, const char *new, const void *new_ns) |
168 | { |
169 | struct kernfs_node *parent, *kn = NULL; |
170 | const void *old_ns = NULL; |
171 | int result; |
172 | |
173 | if (!kobj) |
174 | parent = sysfs_root_kn; |
175 | else |
176 | parent = kobj->sd; |
177 | |
178 | if (targ->sd) |
179 | old_ns = targ->sd->ns; |
180 | |
181 | result = -ENOENT; |
182 | kn = kernfs_find_and_get_ns(parent, name: old, ns: old_ns); |
183 | if (!kn) |
184 | goto out; |
185 | |
186 | result = -EINVAL; |
187 | if (kernfs_type(kn) != KERNFS_LINK) |
188 | goto out; |
189 | if (kn->symlink.target_kn->priv != targ) |
190 | goto out; |
191 | |
192 | result = kernfs_rename_ns(kn, new_parent: parent, new_name: new, new_ns); |
193 | |
194 | out: |
195 | kernfs_put(kn); |
196 | return result; |
197 | } |
198 | EXPORT_SYMBOL_GPL(sysfs_rename_link_ns); |
199 | |