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         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
 135 out1:
 136         dput(dentry);
 137         dentry = ERR_PTR(error);
 138 out:
 139         mutex_unlock(&dir->i_mutex);
 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, %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  */
 166 struct 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 }
 172 EXPORT_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  */
 187 void 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 }
 209 EXPORT_SYMBOL_GPL(securityfs_remove);
 210
 211 static 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
 225 core_initcall(securityfs_init);
 226 MODULE_LICENSE("GPL");
 227