1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * fs/sysfs/dir.c - sysfs core and dir operation 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 #define pr_fmt(fmt) "sysfs: " fmt
13
14 #include <linux/fs.h>
15 #include <linux/kobject.h>
16 #include <linux/slab.h>
17 #include "sysfs.h"
18
19 DEFINE_SPINLOCK(sysfs_symlink_target_lock);
20
21 void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
22 {
23 char *buf;
24
25 buf = kzalloc(PATH_MAX, GFP_KERNEL);
26 if (buf)
27 kernfs_path(parent, buf, PATH_MAX);
28
29 pr_warn("cannot create duplicate filename '%s/%s'\n", buf, name);
30 dump_stack();
31
32 kfree(buf);
33 }
34
35 /**
36 * sysfs_create_dir_ns - create a directory for an object with a namespace tag
37 * @kobj: object we're creating directory for
38 * @ns: the namespace tag to use
39 */
40 int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
41 {
42 struct kernfs_node *parent, *kn;
43 kuid_t uid;
44 kgid_t gid;
45
46 if (WARN_ON(!kobj))
47 return -EINVAL;
48
49 if (kobj->parent)
50 parent = kobj->parent->sd;
51 else
52 parent = sysfs_root_kn;
53
54 if (!parent)
55 return -ENOENT;
56
57 kobject_get_ownership(kobj, &uid, &gid);
58
59 kn = kernfs_create_dir_ns(parent, kobject_name(kobj), 0755, uid, gid,
60 kobj, ns);
61 if (IS_ERR(kn)) {
62 if (PTR_ERR(kn) == -EEXIST)
63 sysfs_warn_dup(parent, kobject_name(kobj));
64 return PTR_ERR(kn);
65 }
66
67 kobj->sd = kn;
68 return 0;
69 }
70
71 /**
72 * sysfs_remove_dir - remove an object's directory.
73 * @kobj: object.
74 *
75 * The only thing special about this is that we remove any files in
76 * the directory before we remove the directory, and we've inlined
77 * what used to be sysfs_rmdir() below, instead of calling separately.
78 */
79 void sysfs_remove_dir(struct kobject *kobj)
80 {
81 struct kernfs_node *kn = kobj->sd;
82
83 /*
84 * In general, kobject owner is responsible for ensuring removal
85 * doesn't race with other operations and sysfs doesn't provide any
86 * protection; however, when @kobj is used as a symlink target, the
87 * symlinking entity usually doesn't own @kobj and thus has no
88 * control over removal. @kobj->sd may be removed anytime
89 * and symlink code may end up dereferencing an already freed node.
90 *
91 * sysfs_symlink_target_lock synchronizes @kobj->sd
92 * disassociation against symlink operations so that symlink code
93 * can safely dereference @kobj->sd.
94 */
95 spin_lock(&sysfs_symlink_target_lock);
96 kobj->sd = NULL;
97 spin_unlock(&sysfs_symlink_target_lock);
98
99 if (kn) {
100 WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
101 kernfs_remove(kn);
102 }
103 }
104
105 int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
106 const void *new_ns)
107 {
108 struct kernfs_node *parent;
109 int ret;
110
111 parent = kernfs_get_parent(kobj->sd);
112 ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
113 kernfs_put(parent);
114 return ret;
115 }
116
117 int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
118 const void *new_ns)
119 {
120 struct kernfs_node *kn = kobj->sd;
121 struct kernfs_node *new_parent;
122
123 new_parent = new_parent_kobj && new_parent_kobj->sd ?
124 new_parent_kobj->sd : sysfs_root_kn;
125
126 return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
127 }
128
129 /**
130 * sysfs_create_mount_point - create an always empty directory
131 * @parent_kobj: kobject that will contain this always empty directory
132 * @name: The name of the always empty directory to add
133 */
134 int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
135 {
136 struct kernfs_node *kn, *parent = parent_kobj->sd;
137
138 kn = kernfs_create_empty_dir(parent, name);
139 if (IS_ERR(kn)) {
140 if (PTR_ERR(kn) == -EEXIST)
141 sysfs_warn_dup(parent, name);
142 return PTR_ERR(kn);
143 }
144
145 return 0;
146 }
147 EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
148
149 /**
150 * sysfs_remove_mount_point - remove an always empty directory.
151 * @parent_kobj: kobject that will contain this always empty directory
152 * @name: The name of the always empty directory to remove
153 *
154 */
155 void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
156 {
157 struct kernfs_node *parent = parent_kobj->sd;
158
159 kernfs_remove_by_name_ns(parent, name, NULL);
160 }
161 EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);
162
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