projects/linux·blob v4.3 · refs

227 lines · 6.5 KiB

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