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