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 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 int __init securityfs_init(void)
 219 {
 220         int retval;
 221
 222         retval = sysfs_create_mount_point(kernel_kobj, "security");
 223         if (retval)
 224                 return retval;
 225
 226         retval = register_filesystem(&fs_type);
 227         if (retval)
 228                 sysfs_remove_mount_point(kernel_kobj, "security");
 229         return retval;
 230 }
 231
 232 core_initcall(securityfs_init);
 233 MODULE_LICENSE("GPL");
 234