xref: /openbmc/linux/security/inode.c (revision d7a3d85e)
1 /*
2  *  inode.c - securityfs
3  *
4  *  Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
5  *
6  *	This program is free software; you can redistribute it and/or
7  *	modify it under the terms of the GNU General Public License version
8  *	2 as published by the Free Software Foundation.
9  *
10  *  Based on fs/debugfs/inode.c which had the following copyright notice:
11  *    Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
12  *    Copyright (C) 2004 IBM Inc.
13  */
14 
15 /* #define DEBUG */
16 #include <linux/module.h>
17 #include <linux/fs.h>
18 #include <linux/mount.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/namei.h>
22 #include <linux/security.h>
23 #include <linux/magic.h>
24 
25 static struct vfsmount *mount;
26 static int mount_count;
27 
28 static inline int positive(struct dentry *dentry)
29 {
30 	return d_really_is_positive(dentry) && !d_unhashed(dentry);
31 }
32 
33 static int fill_super(struct super_block *sb, void *data, int silent)
34 {
35 	static struct tree_descr files[] = {{""}};
36 
37 	return simple_fill_super(sb, SECURITYFS_MAGIC, files);
38 }
39 
40 static struct dentry *get_sb(struct file_system_type *fs_type,
41 		  int flags, const char *dev_name,
42 		  void *data)
43 {
44 	return mount_single(fs_type, flags, data, fill_super);
45 }
46 
47 static struct file_system_type fs_type = {
48 	.owner =	THIS_MODULE,
49 	.name =		"securityfs",
50 	.mount =	get_sb,
51 	.kill_sb =	kill_litter_super,
52 };
53 
54 /**
55  * securityfs_create_file - create a file in the securityfs filesystem
56  *
57  * @name: a pointer to a string containing the name of the file to create.
58  * @mode: the permission that the file should have
59  * @parent: a pointer to the parent dentry for this file.  This should be a
60  *          directory dentry if set.  If this parameter is %NULL, then the
61  *          file will be created in the root of the securityfs filesystem.
62  * @data: a pointer to something that the caller will want to get to later
63  *        on.  The inode.i_private pointer will point to this value on
64  *        the open() call.
65  * @fops: a pointer to a struct file_operations that should be used for
66  *        this file.
67  *
68  * This is the basic "create a file" function for securityfs.  It allows for a
69  * wide range of flexibility in creating a file, or a directory (if you
70  * want to create a directory, the securityfs_create_dir() function is
71  * recommended to be used instead).
72  *
73  * This function returns a pointer to a dentry if it succeeds.  This
74  * pointer must be passed to the securityfs_remove() function when the file is
75  * to be removed (no automatic cleanup happens if your module is unloaded,
76  * you are responsible here).  If an error occurs, the function will return
77  * the error value (via ERR_PTR).
78  *
79  * If securityfs is not enabled in the kernel, the value %-ENODEV is
80  * returned.
81  */
82 struct dentry *securityfs_create_file(const char *name, umode_t mode,
83 				   struct dentry *parent, void *data,
84 				   const struct file_operations *fops)
85 {
86 	struct dentry *dentry;
87 	int is_dir = S_ISDIR(mode);
88 	struct inode *dir, *inode;
89 	int error;
90 
91 	if (!is_dir) {
92 		BUG_ON(!fops);
93 		mode = (mode & S_IALLUGO) | S_IFREG;
94 	}
95 
96 	pr_debug("securityfs: creating file '%s'\n",name);
97 
98 	error = simple_pin_fs(&fs_type, &mount, &mount_count);
99 	if (error)
100 		return ERR_PTR(error);
101 
102 	if (!parent)
103 		parent = mount->mnt_root;
104 
105 	dir = d_inode(parent);
106 
107 	mutex_lock(&dir->i_mutex);
108 	dentry = lookup_one_len(name, parent, strlen(name));
109 	if (IS_ERR(dentry))
110 		goto out;
111 
112 	if (d_really_is_positive(dentry)) {
113 		error = -EEXIST;
114 		goto out1;
115 	}
116 
117 	inode = new_inode(dir->i_sb);
118 	if (!inode) {
119 		error = -ENOMEM;
120 		goto out1;
121 	}
122 
123 	inode->i_ino = get_next_ino();
124 	inode->i_mode = mode;
125 	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
126 	inode->i_private = data;
127 	if (is_dir) {
128 		inode->i_op = &simple_dir_inode_operations;
129 		inode->i_fop = &simple_dir_operations;
130 		inc_nlink(inode);
131 		inc_nlink(dir);
132 	} else {
133 		inode->i_fop = fops;
134 	}
135 	d_instantiate(dentry, inode);
136 	dget(dentry);
137 	mutex_unlock(&dir->i_mutex);
138 	return dentry;
139 
140 out1:
141 	dput(dentry);
142 	dentry = ERR_PTR(error);
143 out:
144 	mutex_unlock(&dir->i_mutex);
145 	simple_release_fs(&mount, &mount_count);
146 	return dentry;
147 }
148 EXPORT_SYMBOL_GPL(securityfs_create_file);
149 
150 /**
151  * securityfs_create_dir - create a directory in the securityfs filesystem
152  *
153  * @name: a pointer to a string containing the name of the directory to
154  *        create.
155  * @parent: a pointer to the parent dentry for this file.  This should be a
156  *          directory dentry if set.  If this parameter is %NULL, then the
157  *          directory will be created in the root of the securityfs filesystem.
158  *
159  * This function creates a directory in securityfs with the given @name.
160  *
161  * This function returns a pointer to a dentry if it succeeds.  This
162  * pointer must be passed to the securityfs_remove() function when the file is
163  * to be removed (no automatic cleanup happens if your module is unloaded,
164  * you are responsible here).  If an error occurs, %NULL will be returned.
165  *
166  * If securityfs is not enabled in the kernel, the value %-ENODEV is
167  * returned.  It is not wise to check for this value, but rather, check for
168  * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
169  * code.
170  */
171 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
172 {
173 	return securityfs_create_file(name,
174 				      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
175 				      parent, NULL, NULL);
176 }
177 EXPORT_SYMBOL_GPL(securityfs_create_dir);
178 
179 /**
180  * securityfs_remove - removes a file or directory from the securityfs filesystem
181  *
182  * @dentry: a pointer to a the dentry of the file or directory to be removed.
183  *
184  * This function removes a file or directory in securityfs that was previously
185  * created with a call to another securityfs function (like
186  * securityfs_create_file() or variants thereof.)
187  *
188  * This function is required to be called in order for the file to be
189  * removed. No automatic cleanup of files will happen when a module is
190  * removed; you are responsible here.
191  */
192 void securityfs_remove(struct dentry *dentry)
193 {
194 	struct dentry *parent;
195 
196 	if (!dentry || IS_ERR(dentry))
197 		return;
198 
199 	parent = dentry->d_parent;
200 	if (!parent || d_really_is_negative(parent))
201 		return;
202 
203 	mutex_lock(&d_inode(parent)->i_mutex);
204 	if (positive(dentry)) {
205 		if (d_really_is_positive(dentry)) {
206 			if (d_is_dir(dentry))
207 				simple_rmdir(d_inode(parent), dentry);
208 			else
209 				simple_unlink(d_inode(parent), dentry);
210 			dput(dentry);
211 		}
212 	}
213 	mutex_unlock(&d_inode(parent)->i_mutex);
214 	simple_release_fs(&mount, &mount_count);
215 }
216 EXPORT_SYMBOL_GPL(securityfs_remove);
217 
218 static struct kobject *security_kobj;
219 
220 static int __init securityfs_init(void)
221 {
222 	int retval;
223 
224 	security_kobj = kobject_create_and_add("security", kernel_kobj);
225 	if (!security_kobj)
226 		return -EINVAL;
227 
228 	retval = register_filesystem(&fs_type);
229 	if (retval)
230 		kobject_put(security_kobj);
231 	return retval;
232 }
233 
234 core_initcall(securityfs_init);
235 MODULE_LICENSE("GPL");
236 
237