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 
sysfs_warn_dup(struct kernfs_node * parent,const char * name)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  */
sysfs_create_dir_ns(struct kobject * kobj,const void * ns)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),
60 				  S_IRWXU | S_IRUGO | S_IXUGO, uid, gid,
61 				  kobj, ns);
62 	if (IS_ERR(kn)) {
63 		if (PTR_ERR(kn) == -EEXIST)
64 			sysfs_warn_dup(parent, kobject_name(kobj));
65 		return PTR_ERR(kn);
66 	}
67 
68 	kobj->sd = kn;
69 	return 0;
70 }
71 
72 /**
73  *	sysfs_remove_dir - remove an object's directory.
74  *	@kobj:	object.
75  *
76  *	The only thing special about this is that we remove any files in
77  *	the directory before we remove the directory, and we've inlined
78  *	what used to be sysfs_rmdir() below, instead of calling separately.
79  */
sysfs_remove_dir(struct kobject * kobj)80 void sysfs_remove_dir(struct kobject *kobj)
81 {
82 	struct kernfs_node *kn = kobj->sd;
83 
84 	/*
85 	 * In general, kboject owner is responsible for ensuring removal
86 	 * doesn't race with other operations and sysfs doesn't provide any
87 	 * protection; however, when @kobj is used as a symlink target, the
88 	 * symlinking entity usually doesn't own @kobj and thus has no
89 	 * control over removal.  @kobj->sd may be removed anytime
90 	 * and symlink code may end up dereferencing an already freed node.
91 	 *
92 	 * sysfs_symlink_target_lock synchronizes @kobj->sd
93 	 * disassociation against symlink operations so that symlink code
94 	 * can safely dereference @kobj->sd.
95 	 */
96 	spin_lock(&sysfs_symlink_target_lock);
97 	kobj->sd = NULL;
98 	spin_unlock(&sysfs_symlink_target_lock);
99 
100 	if (kn) {
101 		WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
102 		kernfs_remove(kn);
103 	}
104 }
105 
sysfs_rename_dir_ns(struct kobject * kobj,const char * new_name,const void * new_ns)106 int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
107 			const void *new_ns)
108 {
109 	struct kernfs_node *parent;
110 	int ret;
111 
112 	parent = kernfs_get_parent(kobj->sd);
113 	ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
114 	kernfs_put(parent);
115 	return ret;
116 }
117 
sysfs_move_dir_ns(struct kobject * kobj,struct kobject * new_parent_kobj,const void * new_ns)118 int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
119 		      const void *new_ns)
120 {
121 	struct kernfs_node *kn = kobj->sd;
122 	struct kernfs_node *new_parent;
123 
124 	new_parent = new_parent_kobj && new_parent_kobj->sd ?
125 		new_parent_kobj->sd : sysfs_root_kn;
126 
127 	return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
128 }
129 
130 /**
131  * sysfs_create_mount_point - create an always empty directory
132  * @parent_kobj:  kobject that will contain this always empty directory
133  * @name: The name of the always empty directory to add
134  */
sysfs_create_mount_point(struct kobject * parent_kobj,const char * name)135 int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
136 {
137 	struct kernfs_node *kn, *parent = parent_kobj->sd;
138 
139 	kn = kernfs_create_empty_dir(parent, name);
140 	if (IS_ERR(kn)) {
141 		if (PTR_ERR(kn) == -EEXIST)
142 			sysfs_warn_dup(parent, name);
143 		return PTR_ERR(kn);
144 	}
145 
146 	return 0;
147 }
148 EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
149 
150 /**
151  *	sysfs_remove_mount_point - remove an always empty directory.
152  *	@parent_kobj: kobject that will contain this always empty directory
153  *	@name: The name of the always empty directory to remove
154  *
155  */
sysfs_remove_mount_point(struct kobject * parent_kobj,const char * name)156 void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
157 {
158 	struct kernfs_node *parent = parent_kobj->sd;
159 
160 	kernfs_remove_by_name_ns(parent, name, NULL);
161 }
162 EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);
163