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/sysfs.h>
  17 #include <linux/kobject.h>
  18 #include <linux/fs.h>
  19 #include <linux/mount.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/init.h>
  22 #include <linux/namei.h>
  23 #include <linux/security.h>
  24 #include <linux/lsm_hooks.h>
  25 #include <linux/magic.h>
  26
  27 static struct vfsmount *mount;
  28 static int mount_count;
  29
  30 static void securityfs_free_inode(struct inode *inode)
  31 {
  32         if (S_ISLNK(inode->i_mode))
  33                 kfree(inode->i_link);
  34         free_inode_nonrcu(inode);
  35 }
  36
  37 static const struct super_operations securityfs_super_operations = {
  38         .statfs         = simple_statfs,
  39         .free_inode     = securityfs_free_inode,
  40 };
  41
  42 static int fill_super(struct super_block *sb, void *data, int silent)
  43 {
  44         static const struct tree_descr files[] = {{""}};
  45         int error;
  46
  47         error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
  48         if (error)
  49                 return error;
  50
  51         sb->s_op = &securityfs_super_operations;
  52
  53         return 0;
  54 }
  55
  56 static struct dentry *get_sb(struct file_system_type *fs_type,
  57                   int flags, const char *dev_name,
  58                   void *data)
  59 {
  60         return mount_single(fs_type, flags, data, fill_super);
  61 }
  62
  63 static struct file_system_type fs_type = {
  64         .owner =        THIS_MODULE,
  65         .name =         "securityfs",
  66         .mount =        get_sb,
  67         .kill_sb =      kill_litter_super,
  68 };
  69
  70 /**
  71  * securityfs_create_dentry - create a dentry in the securityfs filesystem
  72  *
  73  * @name: a pointer to a string containing the name of the file to create.
  74  * @mode: the permission that the file should have
  75  * @parent: a pointer to the parent dentry for this file.  This should be a
  76  *          directory dentry if set.  If this parameter is %NULL, then the
  77  *          file will be created in the root of the securityfs filesystem.
  78  * @data: a pointer to something that the caller will want to get to later
  79  *        on.  The inode.i_private pointer will point to this value on
  80  *        the open() call.
  81  * @fops: a pointer to a struct file_operations that should be used for
  82  *        this file.
  83  * @iops: a point to a struct of inode_operations that should be used for
  84  *        this file/dir
  85  *
  86  * This is the basic "create a file/dir/symlink" function for
  87  * securityfs.  It allows for a wide range of flexibility in creating
  88  * a file, or a directory (if you want to create a directory, the
  89  * securityfs_create_dir() function is recommended to be used
  90  * instead).
  91  *
  92  * This function returns a pointer to a dentry if it succeeds.  This
  93  * pointer must be passed to the securityfs_remove() function when the
  94  * file is to be removed (no automatic cleanup happens if your module
  95  * is unloaded, you are responsible here).  If an error occurs, the
  96  * function will return the error value (via ERR_PTR).
  97  *
  98  * If securityfs is not enabled in the kernel, the value %-ENODEV is
  99  * returned.
 100  */
 101 static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
 102                                         struct dentry *parent, void *data,
 103                                         const struct file_operations *fops,
 104                                         const struct inode_operations *iops)
 105 {
 106         struct dentry *dentry;
 107         struct inode *dir, *inode;
 108         int error;
 109
 110         if (!(mode & S_IFMT))
 111                 mode = (mode & S_IALLUGO) | S_IFREG;
 112
 113         pr_debug("securityfs: creating file '%s'\n",name);
 114
 115         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 116         if (error)
 117                 return ERR_PTR(error);
 118
 119         if (!parent)
 120                 parent = mount->mnt_root;
 121
 122         dir = d_inode(parent);
 123
 124         inode_lock(dir);
 125         dentry = lookup_one_len(name, parent, strlen(name));
 126         if (IS_ERR(dentry))
 127                 goto out;
 128
 129         if (d_really_is_positive(dentry)) {
 130                 error = -EEXIST;
 131                 goto out1;
 132         }
 133
 134         inode = new_inode(dir->i_sb);
 135         if (!inode) {
 136                 error = -ENOMEM;
 137                 goto out1;
 138         }
 139
 140         inode->i_ino = get_next_ino();
 141         inode->i_mode = mode;
 142         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 143         inode->i_private = data;
 144         if (S_ISDIR(mode)) {
 145                 inode->i_op = &simple_dir_inode_operations;
 146                 inode->i_fop = &simple_dir_operations;
 147                 inc_nlink(inode);
 148                 inc_nlink(dir);
 149         } else if (S_ISLNK(mode)) {
 150                 inode->i_op = iops ? iops : &simple_symlink_inode_operations;
 151                 inode->i_link = data;
 152         } else {
 153                 inode->i_fop = fops;
 154         }
 155         d_instantiate(dentry, inode);
 156         dget(dentry);
 157         inode_unlock(dir);
 158         return dentry;
 159
 160 out1:
 161         dput(dentry);
 162         dentry = ERR_PTR(error);
 163 out:
 164         inode_unlock(dir);
 165         simple_release_fs(&mount, &mount_count);
 166         return dentry;
 167 }
 168
 169 /**
 170  * securityfs_create_file - create a file in the securityfs filesystem
 171  *
 172  * @name: a pointer to a string containing the name of the file to create.
 173  * @mode: the permission that the file should have
 174  * @parent: a pointer to the parent dentry for this file.  This should be a
 175  *          directory dentry if set.  If this parameter is %NULL, then the
 176  *          file will be created in the root of the securityfs filesystem.
 177  * @data: a pointer to something that the caller will want to get to later
 178  *        on.  The inode.i_private pointer will point to this value on
 179  *        the open() call.
 180  * @fops: a pointer to a struct file_operations that should be used for
 181  *        this file.
 182  *
 183  * This function creates a file in securityfs with the given @name.
 184  *
 185  * This function returns a pointer to a dentry if it succeeds.  This
 186  * pointer must be passed to the securityfs_remove() function when the file is
 187  * to be removed (no automatic cleanup happens if your module is unloaded,
 188  * you are responsible here).  If an error occurs, the function will return
 189  * the error value (via ERR_PTR).
 190  *
 191  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 192  * returned.
 193  */
 194 struct dentry *securityfs_create_file(const char *name, umode_t mode,
 195                                       struct dentry *parent, void *data,
 196                                       const struct file_operations *fops)
 197 {
 198         return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
 199 }
 200 EXPORT_SYMBOL_GPL(securityfs_create_file);
 201
 202 /**
 203  * securityfs_create_dir - create a directory in the securityfs filesystem
 204  *
 205  * @name: a pointer to a string containing the name of the directory to
 206  *        create.
 207  * @parent: a pointer to the parent dentry for this file.  This should be a
 208  *          directory dentry if set.  If this parameter is %NULL, then the
 209  *          directory will be created in the root of the securityfs filesystem.
 210  *
 211  * This function creates a directory in securityfs with the given @name.
 212  *
 213  * This function returns a pointer to a dentry if it succeeds.  This
 214  * pointer must be passed to the securityfs_remove() function when the file is
 215  * to be removed (no automatic cleanup happens if your module is unloaded,
 216  * you are responsible here).  If an error occurs, the function will return
 217  * the error value (via ERR_PTR).
 218  *
 219  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 220  * returned.
 221  */
 222 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 223 {
 224         return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL);
 225 }
 226 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 227
 228 /**
 229  * securityfs_create_symlink - create a symlink in the securityfs filesystem
 230  *
 231  * @name: a pointer to a string containing the name of the symlink to
 232  *        create.
 233  * @parent: a pointer to the parent dentry for the symlink.  This should be a
 234  *          directory dentry if set.  If this parameter is %NULL, then the
 235  *          directory will be created in the root of the securityfs filesystem.
 236  * @target: a pointer to a string containing the name of the symlink's target.
 237  *          If this parameter is %NULL, then the @iops parameter needs to be
 238  *          setup to handle .readlink and .get_link inode_operations.
 239  * @iops: a pointer to the struct inode_operations to use for the symlink. If
 240  *        this parameter is %NULL, then the default simple_symlink_inode
 241  *        operations will be used.
 242  *
 243  * This function creates a symlink in securityfs with the given @name.
 244  *
 245  * This function returns a pointer to a dentry if it succeeds.  This
 246  * pointer must be passed to the securityfs_remove() function when the file is
 247  * to be removed (no automatic cleanup happens if your module is unloaded,
 248  * you are responsible here).  If an error occurs, the function will return
 249  * the error value (via ERR_PTR).
 250  *
 251  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 252  * returned.
 253  */
 254 struct dentry *securityfs_create_symlink(const char *name,
 255                                          struct dentry *parent,
 256                                          const char *target,
 257                                          const struct inode_operations *iops)
 258 {
 259         struct dentry *dent;
 260         char *link = NULL;
 261
 262         if (target) {
 263                 link = kstrdup(target, GFP_KERNEL);
 264                 if (!link)
 265                         return ERR_PTR(-ENOMEM);
 266         }
 267         dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
 268                                         link, NULL, iops);
 269         if (IS_ERR(dent))
 270                 kfree(link);
 271
 272         return dent;
 273 }
 274 EXPORT_SYMBOL_GPL(securityfs_create_symlink);
 275
 276 /**
 277  * securityfs_remove - removes a file or directory from the securityfs filesystem
 278  *
 279  * @dentry: a pointer to a the dentry of the file or directory to be removed.
 280  *
 281  * This function removes a file or directory in securityfs that was previously
 282  * created with a call to another securityfs function (like
 283  * securityfs_create_file() or variants thereof.)
 284  *
 285  * This function is required to be called in order for the file to be
 286  * removed. No automatic cleanup of files will happen when a module is
 287  * removed; you are responsible here.
 288  */
 289 void securityfs_remove(struct dentry *dentry)
 290 {
 291         struct inode *dir;
 292
 293         if (!dentry || IS_ERR(dentry))
 294                 return;
 295
 296         dir = d_inode(dentry->d_parent);
 297         inode_lock(dir);
 298         if (simple_positive(dentry)) {
 299                 if (d_is_dir(dentry))
 300                         simple_rmdir(dir, dentry);
 301                 else
 302                         simple_unlink(dir, dentry);
 303                 dput(dentry);
 304         }
 305         inode_unlock(dir);
 306         simple_release_fs(&mount, &mount_count);
 307 }
 308 EXPORT_SYMBOL_GPL(securityfs_remove);
 309
 310 #ifdef CONFIG_SECURITY
 311 static struct dentry *lsm_dentry;
 312 static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
 313                         loff_t *ppos)
 314 {
 315         return simple_read_from_buffer(buf, count, ppos, lsm_names,
 316                 strlen(lsm_names));
 317 }
 318
 319 static const struct file_operations lsm_ops = {
 320         .read = lsm_read,
 321         .llseek = generic_file_llseek,
 322 };
 323 #endif
 324
 325 static int __init securityfs_init(void)
 326 {
 327         int retval;
 328
 329         retval = sysfs_create_mount_point(kernel_kobj, "security");
 330         if (retval)
 331                 return retval;
 332
 333         retval = register_filesystem(&fs_type);
 334         if (retval) {
 335                 sysfs_remove_mount_point(kernel_kobj, "security");
 336                 return retval;
 337         }
 338 #ifdef CONFIG_SECURITY
 339         lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
 340                                                 &lsm_ops);
 341 #endif
 342         return 0;
 343 }
 344 core_initcall(securityfs_init);