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Linux/security/inode.c

  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 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 
 35 static 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 
 42 static 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  */
 77 struct 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         inode_lock(dir);
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(inode);
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         inode_unlock(dir);
133         return dentry;
134 
135 out1:
136         dput(dentry);
137         dentry = ERR_PTR(error);
138 out:
139         inode_unlock(dir);
140         simple_release_fs(&mount, &mount_count);
141         return dentry;
142 }
143 EXPORT_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, the function will return
160  * the error value (via ERR_PTR).
161  *
162  * If securityfs is not enabled in the kernel, the value %-ENODEV is
163  * returned.
164  */
165 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
166 {
167         return securityfs_create_file(name,
168                                       S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
169                                       parent, NULL, NULL);
170 }
171 EXPORT_SYMBOL_GPL(securityfs_create_dir);
172 
173 /**
174  * securityfs_remove - removes a file or directory from the securityfs filesystem
175  *
176  * @dentry: a pointer to a the dentry of the file or directory to be removed.
177  *
178  * This function removes a file or directory in securityfs that was previously
179  * created with a call to another securityfs function (like
180  * securityfs_create_file() or variants thereof.)
181  *
182  * This function is required to be called in order for the file to be
183  * removed. No automatic cleanup of files will happen when a module is
184  * removed; you are responsible here.
185  */
186 void securityfs_remove(struct dentry *dentry)
187 {
188         struct inode *dir;
189 
190         if (!dentry || IS_ERR(dentry))
191                 return;
192 
193         dir = d_inode(dentry->d_parent);
194         inode_lock(dir);
195         if (simple_positive(dentry)) {
196                 if (d_is_dir(dentry))
197                         simple_rmdir(dir, dentry);
198                 else
199                         simple_unlink(dir, dentry);
200                 dput(dentry);
201         }
202         inode_unlock(dir);
203         simple_release_fs(&mount, &mount_count);
204 }
205 EXPORT_SYMBOL_GPL(securityfs_remove);
206 
207 static int __init securityfs_init(void)
208 {
209         int retval;
210 
211         retval = sysfs_create_mount_point(kernel_kobj, "security");
212         if (retval)
213                 return retval;
214 
215         retval = register_filesystem(&fs_type);
216         if (retval)
217                 sysfs_remove_mount_point(kernel_kobj, "security");
218         return retval;
219 }
220 
221 core_initcall(securityfs_init);
222 MODULE_LICENSE("GPL");
223 
224 

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