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 void securityfs_i_callback(struct rcu_head *head)
  30 {
  31         struct inode *inode = container_of(head, struct inode, i_rcu);
  32         if (S_ISLNK(inode->i_mode))
  33                 kfree(inode->i_link);
  34         free_inode_nonrcu(inode);
  35 }
  36
  37 static void securityfs_destroy_inode(struct inode *inode)
  38 {
  39         call_rcu(&inode->i_rcu, securityfs_i_callback);
  40 }
  41
  42 static const struct super_operations securityfs_super_operations = {
  43         .statfs         = simple_statfs,
  44         .destroy_inode  = securityfs_destroy_inode,
  45 };
  46
  47 static int fill_super(struct super_block *sb, void *data, int silent)
  48 {
  49         static const struct tree_descr files[] = {{""}};
  50         int error;
  51
  52         error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
  53         if (error)
  54                 return error;
  55
  56         sb->s_op = &securityfs_super_operations;
  57
  58         return 0;
  59 }
  60
  61 static struct dentry *get_sb(struct file_system_type *fs_type,
  62                   int flags, const char *dev_name,
  63                   void *data)
  64 {
  65         return mount_single(fs_type, flags, data, fill_super);
  66 }
  67
  68 static struct file_system_type fs_type = {
  69         .owner =        THIS_MODULE,
  70         .name =         "securityfs",
  71         .mount =        get_sb,
  72         .kill_sb =      kill_litter_super,
  73 };
  74
  75 /**
  76  * securityfs_create_dentry - create a dentry in the securityfs filesystem
  77  *
  78  * @name: a pointer to a string containing the name of the file to create.
  79  * @mode: the permission that the file should have
  80  * @parent: a pointer to the parent dentry for this file.  This should be a
  81  *          directory dentry if set.  If this parameter is %NULL, then the
  82  *          file will be created in the root of the securityfs filesystem.
  83  * @data: a pointer to something that the caller will want to get to later
  84  *        on.  The inode.i_private pointer will point to this value on
  85  *        the open() call.
  86  * @fops: a pointer to a struct file_operations that should be used for
  87  *        this file.
  88  * @iops: a point to a struct of inode_operations that should be used for
  89  *        this file/dir
  90  *
  91  * This is the basic "create a file/dir/symlink" function for
  92  * securityfs.  It allows for a wide range of flexibility in creating
  93  * a file, or a directory (if you want to create a directory, the
  94  * securityfs_create_dir() function is recommended to be used
  95  * instead).
  96  *
  97  * This function returns a pointer to a dentry if it succeeds.  This
  98  * pointer must be passed to the securityfs_remove() function when the
  99  * file is to be removed (no automatic cleanup happens if your module
 100  * is unloaded, you are responsible here).  If an error occurs, the
 101  * function will return the error value (via ERR_PTR).
 102  *
 103  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 104  * returned.
 105  */
 106 static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
 107                                         struct dentry *parent, void *data,
 108                                         const struct file_operations *fops,
 109                                         const struct inode_operations *iops)
 110 {
 111         struct dentry *dentry;
 112         struct inode *dir, *inode;
 113         int error;
 114
 115         if (!(mode & S_IFMT))
 116                 mode = (mode & S_IALLUGO) | S_IFREG;
 117
 118         pr_debug("securityfs: creating file '%s'\n",name);
 119
 120         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 121         if (error)
 122                 return ERR_PTR(error);
 123
 124         if (!parent)
 125                 parent = mount->mnt_root;
 126
 127         dir = d_inode(parent);
 128
 129         inode_lock(dir);
 130         dentry = lookup_one_len(name, parent, strlen(name));
 131         if (IS_ERR(dentry))
 132                 goto out;
 133
 134         if (d_really_is_positive(dentry)) {
 135                 error = -EEXIST;
 136                 goto out1;
 137         }
 138
 139         inode = new_inode(dir->i_sb);
 140         if (!inode) {
 141                 error = -ENOMEM;
 142                 goto out1;
 143         }
 144
 145         inode->i_ino = get_next_ino();
 146         inode->i_mode = mode;
 147         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 148         inode->i_private = data;
 149         if (S_ISDIR(mode)) {
 150                 inode->i_op = &simple_dir_inode_operations;
 151                 inode->i_fop = &simple_dir_operations;
 152                 inc_nlink(inode);
 153                 inc_nlink(dir);
 154         } else if (S_ISLNK(mode)) {
 155                 inode->i_op = iops ? iops : &simple_symlink_inode_operations;
 156                 inode->i_link = data;
 157         } else {
 158                 inode->i_fop = fops;
 159         }
 160         d_instantiate(dentry, inode);
 161         dget(dentry);
 162         inode_unlock(dir);
 163         return dentry;
 164
 165 out1:
 166         dput(dentry);
 167         dentry = ERR_PTR(error);
 168 out:
 169         inode_unlock(dir);
 170         simple_release_fs(&mount, &mount_count);
 171         return dentry;
 172 }
 173
 174 /**
 175  * securityfs_create_file - create a file in the securityfs filesystem
 176  *
 177  * @name: a pointer to a string containing the name of the file to create.
 178  * @mode: the permission that the file should have
 179  * @parent: a pointer to the parent dentry for this file.  This should be a
 180  *          directory dentry if set.  If this parameter is %NULL, then the
 181  *          file will be created in the root of the securityfs filesystem.
 182  * @data: a pointer to something that the caller will want to get to later
 183  *        on.  The inode.i_private pointer will point to this value on
 184  *        the open() call.
 185  * @fops: a pointer to a struct file_operations that should be used for
 186  *        this file.
 187  *
 188  * This function creates a file in securityfs with the given @name.
 189  *
 190  * This function returns a pointer to a dentry if it succeeds.  This
 191  * pointer must be passed to the securityfs_remove() function when the file is
 192  * to be removed (no automatic cleanup happens if your module is unloaded,
 193  * you are responsible here).  If an error occurs, the function will return
 194  * the error value (via ERR_PTR).
 195  *
 196  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 197  * returned.
 198  */
 199 struct dentry *securityfs_create_file(const char *name, umode_t mode,
 200                                       struct dentry *parent, void *data,
 201                                       const struct file_operations *fops)
 202 {
 203         return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
 204 }
 205 EXPORT_SYMBOL_GPL(securityfs_create_file);
 206
 207 /**
 208  * securityfs_create_dir - create a directory in the securityfs filesystem
 209  *
 210  * @name: a pointer to a string containing the name of the directory to
 211  *        create.
 212  * @parent: a pointer to the parent dentry for this file.  This should be a
 213  *          directory dentry if set.  If this parameter is %NULL, then the
 214  *          directory will be created in the root of the securityfs filesystem.
 215  *
 216  * This function creates a directory in securityfs with the given @name.
 217  *
 218  * This function returns a pointer to a dentry if it succeeds.  This
 219  * pointer must be passed to the securityfs_remove() function when the file is
 220  * to be removed (no automatic cleanup happens if your module is unloaded,
 221  * you are responsible here).  If an error occurs, the function will return
 222  * the error value (via ERR_PTR).
 223  *
 224  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 225  * returned.
 226  */
 227 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 228 {
 229         return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL);
 230 }
 231 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 232
 233 /**
 234  * securityfs_create_symlink - create a symlink in the securityfs filesystem
 235  *
 236  * @name: a pointer to a string containing the name of the symlink to
 237  *        create.
 238  * @parent: a pointer to the parent dentry for the symlink.  This should be a
 239  *          directory dentry if set.  If this parameter is %NULL, then the
 240  *          directory will be created in the root of the securityfs filesystem.
 241  * @target: a pointer to a string containing the name of the symlink's target.
 242  *          If this parameter is %NULL, then the @iops parameter needs to be
 243  *          setup to handle .readlink and .get_link inode_operations.
 244  * @iops: a pointer to the struct inode_operations to use for the symlink. If
 245  *        this parameter is %NULL, then the default simple_symlink_inode
 246  *        operations will be used.
 247  *
 248  * This function creates a symlink in securityfs with the given @name.
 249  *
 250  * This function returns a pointer to a dentry if it succeeds.  This
 251  * pointer must be passed to the securityfs_remove() function when the file is
 252  * to be removed (no automatic cleanup happens if your module is unloaded,
 253  * you are responsible here).  If an error occurs, the function will return
 254  * the error value (via ERR_PTR).
 255  *
 256  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 257  * returned.
 258  */
 259 struct dentry *securityfs_create_symlink(const char *name,
 260                                          struct dentry *parent,
 261                                          const char *target,
 262                                          const struct inode_operations *iops)
 263 {
 264         struct dentry *dent;
 265         char *link = NULL;
 266
 267         if (target) {
 268                 link = kstrdup(target, GFP_KERNEL);
 269                 if (!link)
 270                         return ERR_PTR(-ENOMEM);
 271         }
 272         dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
 273                                         link, NULL, iops);
 274         if (IS_ERR(dent))
 275                 kfree(link);
 276
 277         return dent;
 278 }
 279 EXPORT_SYMBOL_GPL(securityfs_create_symlink);
 280
 281 /**
 282  * securityfs_remove - removes a file or directory from the securityfs filesystem
 283  *
 284  * @dentry: a pointer to a the dentry of the file or directory to be removed.
 285  *
 286  * This function removes a file or directory in securityfs that was previously
 287  * created with a call to another securityfs function (like
 288  * securityfs_create_file() or variants thereof.)
 289  *
 290  * This function is required to be called in order for the file to be
 291  * removed. No automatic cleanup of files will happen when a module is
 292  * removed; you are responsible here.
 293  */
 294 void securityfs_remove(struct dentry *dentry)
 295 {
 296         struct inode *dir;
 297
 298         if (!dentry || IS_ERR(dentry))
 299                 return;
 300
 301         dir = d_inode(dentry->d_parent);
 302         inode_lock(dir);
 303         if (simple_positive(dentry)) {
 304                 if (d_is_dir(dentry))
 305                         simple_rmdir(dir, dentry);
 306                 else
 307                         simple_unlink(dir, dentry);
 308                 dput(dentry);
 309         }
 310         inode_unlock(dir);
 311         simple_release_fs(&mount, &mount_count);
 312 }
 313 EXPORT_SYMBOL_GPL(securityfs_remove);
 314
 315 #ifdef CONFIG_SECURITY
 316 static struct dentry *lsm_dentry;
 317 static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
 318                         loff_t *ppos)
 319 {
 320         return simple_read_from_buffer(buf, count, ppos, lsm_names,
 321                 strlen(lsm_names));
 322 }
 323
 324 static const struct file_operations lsm_ops = {
 325         .read = lsm_read,
 326         .llseek = generic_file_llseek,
 327 };
 328 #endif
 329
 330 static int __init securityfs_init(void)
 331 {
 332         int retval;
 333
 334         retval = sysfs_create_mount_point(kernel_kobj, "security");
 335         if (retval)
 336                 return retval;
 337
 338         retval = register_filesystem(&fs_type);
 339         if (retval) {
 340                 sysfs_remove_mount_point(kernel_kobj, "security");
 341                 return retval;
 342         }
 343 #ifdef CONFIG_SECURITY
 344         lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
 345                                                 &lsm_ops);
 346 #endif
 347         return 0;
 348 }
 349
 350 core_initcall(securityfs_init);
 351 MODULE_LICENSE("GPL");
 352