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/lsm_hooks.h>
  24 #include <linux/magic.h>
  25
  26 static struct vfsmount *mount;
  27 static int mount_count;
  28
  29 static int fill_super(struct super_block *sb, void *data, int silent)
  30 {
  31         static const struct tree_descr files[] = {{""}};
  32
  33         return simple_fill_super(sb, SECURITYFS_MAGIC, files);
  34 }
  35
  36 static struct dentry *get_sb(struct file_system_type *fs_type,
  37                   int flags, const char *dev_name,
  38                   void *data)
  39 {
  40         return mount_single(fs_type, flags, data, fill_super);
  41 }
  42
  43 static struct file_system_type fs_type = {
  44         .owner =        THIS_MODULE,
  45         .name =         "securityfs",
  46         .mount =        get_sb,
  47         .kill_sb =      kill_litter_super,
  48 };
  49
  50 /**
  51  * securityfs_create_file - create a file in the securityfs filesystem
  52  *
  53  * @name: a pointer to a string containing the name of the file to create.
  54  * @mode: the permission that the file should have
  55  * @parent: a pointer to the parent dentry for this file.  This should be a
  56  *          directory dentry if set.  If this parameter is %NULL, then the
  57  *          file will be created in the root of the securityfs filesystem.
  58  * @data: a pointer to something that the caller will want to get to later
  59  *        on.  The inode.i_private pointer will point to this value on
  60  *        the open() call.
  61  * @fops: a pointer to a struct file_operations that should be used for
  62  *        this file.
  63  *
  64  * This is the basic "create a file" function for securityfs.  It allows for a
  65  * wide range of flexibility in creating a file, or a directory (if you
  66  * want to create a directory, the securityfs_create_dir() function is
  67  * recommended to be used instead).
  68  *
  69  * This function returns a pointer to a dentry if it succeeds.  This
  70  * pointer must be passed to the securityfs_remove() function when the file is
  71  * to be removed (no automatic cleanup happens if your module is unloaded,
  72  * you are responsible here).  If an error occurs, the function will return
  73  * the error value (via ERR_PTR).
  74  *
  75  * If securityfs is not enabled in the kernel, the value %-ENODEV is
  76  * returned.
  77  */
  78 struct dentry *securityfs_create_file(const char *name, umode_t mode,
  79                                    struct dentry *parent, void *data,
  80                                    const struct file_operations *fops)
  81 {
  82         struct dentry *dentry;
  83         int is_dir = S_ISDIR(mode);
  84         struct inode *dir, *inode;
  85         int error;
  86
  87         if (!is_dir) {
  88                 BUG_ON(!fops);
  89                 mode = (mode & S_IALLUGO) | S_IFREG;
  90         }
  91
  92         pr_debug("securityfs: creating file '%s'\n",name);
  93
  94         error = simple_pin_fs(&fs_type, &mount, &mount_count);
  95         if (error)
  96                 return ERR_PTR(error);
  97
  98         if (!parent)
  99                 parent = mount->mnt_root;
 100
 101         dir = d_inode(parent);
 102
 103         inode_lock(dir);
 104         dentry = lookup_one_len(name, parent, strlen(name));
 105         if (IS_ERR(dentry))
 106                 goto out;
 107
 108         if (d_really_is_positive(dentry)) {
 109                 error = -EEXIST;
 110                 goto out1;
 111         }
 112
 113         inode = new_inode(dir->i_sb);
 114         if (!inode) {
 115                 error = -ENOMEM;
 116                 goto out1;
 117         }
 118
 119         inode->i_ino = get_next_ino();
 120         inode->i_mode = mode;
 121         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 122         inode->i_private = data;
 123         if (is_dir) {
 124                 inode->i_op = &simple_dir_inode_operations;
 125                 inode->i_fop = &simple_dir_operations;
 126                 inc_nlink(inode);
 127                 inc_nlink(dir);
 128         } else {
 129                 inode->i_fop = fops;
 130         }
 131         d_instantiate(dentry, inode);
 132         dget(dentry);
 133         inode_unlock(dir);
 134         return dentry;
 135
 136 out1:
 137         dput(dentry);
 138         dentry = ERR_PTR(error);
 139 out:
 140         inode_unlock(dir);
 141         simple_release_fs(&mount, &mount_count);
 142         return dentry;
 143 }
 144 EXPORT_SYMBOL_GPL(securityfs_create_file);
 145
 146 /**
 147  * securityfs_create_dir - create a directory in the securityfs filesystem
 148  *
 149  * @name: a pointer to a string containing the name of the directory to
 150  *        create.
 151  * @parent: a pointer to the parent dentry for this file.  This should be a
 152  *          directory dentry if set.  If this parameter is %NULL, then the
 153  *          directory will be created in the root of the securityfs filesystem.
 154  *
 155  * This function creates a directory in securityfs with the given @name.
 156  *
 157  * This function returns a pointer to a dentry if it succeeds.  This
 158  * pointer must be passed to the securityfs_remove() function when the file is
 159  * to be removed (no automatic cleanup happens if your module is unloaded,
 160  * you are responsible here).  If an error occurs, the function will return
 161  * the error value (via ERR_PTR).
 162  *
 163  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 164  * returned.
 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 inode *dir;
 190
 191         if (!dentry || IS_ERR(dentry))
 192                 return;
 193
 194         dir = d_inode(dentry->d_parent);
 195         inode_lock(dir);
 196         if (simple_positive(dentry)) {
 197                 if (d_is_dir(dentry))
 198                         simple_rmdir(dir, dentry);
 199                 else
 200                         simple_unlink(dir, dentry);
 201                 dput(dentry);
 202         }
 203         inode_unlock(dir);
 204         simple_release_fs(&mount, &mount_count);
 205 }
 206 EXPORT_SYMBOL_GPL(securityfs_remove);
 207
 208 #ifdef CONFIG_SECURITY
 209 static struct dentry *lsm_dentry;
 210 static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
 211                         loff_t *ppos)
 212 {
 213         return simple_read_from_buffer(buf, count, ppos, lsm_names,
 214                 strlen(lsm_names));
 215 }
 216
 217 static const struct file_operations lsm_ops = {
 218         .read = lsm_read,
 219         .llseek = generic_file_llseek,
 220 };
 221 #endif
 222
 223 static int __init securityfs_init(void)
 224 {
 225         int retval;
 226
 227         retval = sysfs_create_mount_point(kernel_kobj, "security");
 228         if (retval)
 229                 return retval;
 230
 231         retval = register_filesystem(&fs_type);
 232         if (retval) {
 233                 sysfs_remove_mount_point(kernel_kobj, "security");
 234                 return retval;
 235         }
 236 #ifdef CONFIG_SECURITY
 237         lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
 238                                                 &lsm_ops);
 239 #endif
 240         return 0;
 241 }
 242
 243 core_initcall(securityfs_init);
 244 MODULE_LICENSE("GPL");
 245