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/config.h>
  17 #include <linux/module.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
  25 #define SECURITYFS_MAGIC        0x73636673
  26
  27 static struct vfsmount *mount;
  28 static int mount_count;
  29
  30 /*
  31  * TODO:
  32  *   I think I can get rid of these default_file_ops, but not quite sure...
  33  */
  34 static ssize_t default_read_file(struct file *file, char __user *buf,
  35                                  size_t count, loff_t *ppos)
  36 {
  37         return 0;
  38 }
  39
  40 static ssize_t default_write_file(struct file *file, const char __user *buf,
  41                                    size_t count, loff_t *ppos)
  42 {
  43         return count;
  44 }
  45
  46 static int default_open(struct inode *inode, struct file *file)
  47 {
  48         if (inode->u.generic_ip)
  49                 file->private_data = inode->u.generic_ip;
  50
  51         return 0;
  52 }
  53
  54 static struct file_operations default_file_ops = {
  55         .read =         default_read_file,
  56         .write =        default_write_file,
  57         .open =         default_open,
  58 };
  59
  60 static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)
  61 {
  62         struct inode *inode = new_inode(sb);
  63
  64         if (inode) {
  65                 inode->i_mode = mode;
  66                 inode->i_uid = 0;
  67                 inode->i_gid = 0;
  68                 inode->i_blksize = PAGE_CACHE_SIZE;
  69                 inode->i_blocks = 0;
  70                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  71                 switch (mode & S_IFMT) {
  72                 default:
  73                         init_special_inode(inode, mode, dev);
  74                         break;
  75                 case S_IFREG:
  76                         inode->i_fop = &default_file_ops;
  77                         break;
  78                 case S_IFDIR:
  79                         inode->i_op = &simple_dir_inode_operations;
  80                         inode->i_fop = &simple_dir_operations;
  81
  82                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  83                         inode->i_nlink++;
  84                         break;
  85                 }
  86         }
  87         return inode;
  88 }
  89
  90 /* SMP-safe */
  91 static int mknod(struct inode *dir, struct dentry *dentry,
  92                          int mode, dev_t dev)
  93 {
  94         struct inode *inode;
  95         int error = -EPERM;
  96
  97         if (dentry->d_inode)
  98                 return -EEXIST;
  99
 100         inode = get_inode(dir->i_sb, mode, dev);
 101         if (inode) {
 102                 d_instantiate(dentry, inode);
 103                 dget(dentry);
 104                 error = 0;
 105         }
 106         return error;
 107 }
 108
 109 static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
 110 {
 111         int res;
 112
 113         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
 114         res = mknod(dir, dentry, mode, 0);
 115         if (!res)
 116                 dir->i_nlink++;
 117         return res;
 118 }
 119
 120 static int create(struct inode *dir, struct dentry *dentry, int mode)
 121 {
 122         mode = (mode & S_IALLUGO) | S_IFREG;
 123         return mknod(dir, dentry, mode, 0);
 124 }
 125
 126 static inline int positive(struct dentry *dentry)
 127 {
 128         return dentry->d_inode && !d_unhashed(dentry);
 129 }
 130
 131 static int fill_super(struct super_block *sb, void *data, int silent)
 132 {
 133         static struct tree_descr files[] = {{""}};
 134
 135         return simple_fill_super(sb, SECURITYFS_MAGIC, files);
 136 }
 137
 138 static struct super_block *get_sb(struct file_system_type *fs_type,
 139                                         int flags, const char *dev_name,
 140                                         void *data)
 141 {
 142         return get_sb_single(fs_type, flags, data, fill_super);
 143 }
 144
 145 static struct file_system_type fs_type = {
 146         .owner =        THIS_MODULE,
 147         .name =         "securityfs",
 148         .get_sb =       get_sb,
 149         .kill_sb =      kill_litter_super,
 150 };
 151
 152 static int create_by_name(const char *name, mode_t mode,
 153                           struct dentry *parent,
 154                           struct dentry **dentry)
 155 {
 156         int error = 0;
 157
 158         *dentry = NULL;
 159
 160         /* If the parent is not specified, we create it in the root.
 161          * We need the root dentry to do this, which is in the super
 162          * block. A pointer to that is in the struct vfsmount that we
 163          * have around.
 164          */
 165         if (!parent ) {
 166                 if (mount && mount->mnt_sb) {
 167                         parent = mount->mnt_sb->s_root;
 168                 }
 169         }
 170         if (!parent) {
 171                 pr_debug("securityfs: Ah! can not find a parent!\n");
 172                 return -EFAULT;
 173         }
 174
 175         down(&parent->d_inode->i_sem);
 176         *dentry = lookup_one_len(name, parent, strlen(name));
 177         if (!IS_ERR(dentry)) {
 178                 if ((mode & S_IFMT) == S_IFDIR)
 179                         error = mkdir(parent->d_inode, *dentry, mode);
 180                 else
 181                         error = create(parent->d_inode, *dentry, mode);
 182         } else
 183                 error = PTR_ERR(dentry);
 184         up(&parent->d_inode->i_sem);
 185
 186         return error;
 187 }
 188
 189 /**
 190  * securityfs_create_file - create a file in the securityfs filesystem
 191  *
 192  * @name: a pointer to a string containing the name of the file to create.
 193  * @mode: the permission that the file should have
 194  * @parent: a pointer to the parent dentry for this file.  This should be a
 195  *          directory dentry if set.  If this paramater is NULL, then the
 196  *          file will be created in the root of the securityfs filesystem.
 197  * @data: a pointer to something that the caller will want to get to later
 198  *        on.  The inode.u.generic_ip pointer will point to this value on
 199  *        the open() call.
 200  * @fops: a pointer to a struct file_operations that should be used for
 201  *        this file.
 202  *
 203  * This is the basic "create a file" function for securityfs.  It allows for a
 204  * wide range of flexibility in createing a file, or a directory (if you
 205  * want to create a directory, the securityfs_create_dir() function is
 206  * recommended to be used instead.)
 207  *
 208  * This function will return a pointer to a dentry if it succeeds.  This
 209  * pointer must be passed to the securityfs_remove() function when the file is
 210  * to be removed (no automatic cleanup happens if your module is unloaded,
 211  * you are responsible here.)  If an error occurs, NULL will be returned.
 212  *
 213  * If securityfs is not enabled in the kernel, the value -ENODEV will be
 214  * returned.  It is not wise to check for this value, but rather, check for
 215  * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
 216  * code.
 217  */
 218 struct dentry *securityfs_create_file(const char *name, mode_t mode,
 219                                    struct dentry *parent, void *data,
 220                                    struct file_operations *fops)
 221 {
 222         struct dentry *dentry = NULL;
 223         int error;
 224
 225         pr_debug("securityfs: creating file '%s'\n",name);
 226
 227         error = simple_pin_fs("securityfs", &mount, &mount_count);
 228         if (error) {
 229                 dentry = ERR_PTR(error);
 230                 goto exit;
 231         }
 232
 233         error = create_by_name(name, mode, parent, &dentry);
 234         if (error) {
 235                 dentry = ERR_PTR(error);
 236                 simple_release_fs(&mount, &mount_count);
 237                 goto exit;
 238         }
 239
 240         if (dentry->d_inode) {
 241                 if (fops)
 242                         dentry->d_inode->i_fop = fops;
 243                 if (data)
 244                         dentry->d_inode->u.generic_ip = data;
 245         }
 246 exit:
 247         return dentry;
 248 }
 249 EXPORT_SYMBOL_GPL(securityfs_create_file);
 250
 251 /**
 252  * securityfs_create_dir - create a directory in the securityfs filesystem
 253  *
 254  * @name: a pointer to a string containing the name of the directory to
 255  *        create.
 256  * @parent: a pointer to the parent dentry for this file.  This should be a
 257  *          directory dentry if set.  If this paramater is NULL, then the
 258  *          directory will be created in the root of the securityfs filesystem.
 259  *
 260  * This function creates a directory in securityfs with the given name.
 261  *
 262  * This function will return a pointer to a dentry if it succeeds.  This
 263  * pointer must be passed to the securityfs_remove() function when the file is
 264  * to be removed (no automatic cleanup happens if your module is unloaded,
 265  * you are responsible here.)  If an error occurs, NULL will be returned.
 266  *
 267  * If securityfs is not enabled in the kernel, the value -ENODEV will be
 268  * returned.  It is not wise to check for this value, but rather, check for
 269  * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
 270  * code.
 271  */
 272 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 273 {
 274         return securityfs_create_file(name,
 275                                       S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 276                                       parent, NULL, NULL);
 277 }
 278 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 279
 280 /**
 281  * securityfs_remove - removes a file or directory from the securityfs filesystem
 282  *
 283  * @dentry: a pointer to a the dentry of the file or directory to be
 284  *          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 dentry *parent;
 297
 298         if (!dentry)
 299                 return;
 300
 301         parent = dentry->d_parent;
 302         if (!parent || !parent->d_inode)
 303                 return;
 304
 305         down(&parent->d_inode->i_sem);
 306         if (positive(dentry)) {
 307                 if (dentry->d_inode) {
 308                         if (S_ISDIR(dentry->d_inode->i_mode))
 309                                 simple_rmdir(parent->d_inode, dentry);
 310                         else
 311                                 simple_unlink(parent->d_inode, dentry);
 312                         dput(dentry);
 313                 }
 314         }
 315         up(&parent->d_inode->i_sem);
 316         simple_release_fs(&mount, &mount_count);
 317 }
 318 EXPORT_SYMBOL_GPL(securityfs_remove);
 319
 320 static decl_subsys(security, NULL, NULL);
 321
 322 static int __init securityfs_init(void)
 323 {
 324         int retval;
 325
 326         kset_set_kset_s(&security_subsys, kernel_subsys);
 327         retval = subsystem_register(&security_subsys);
 328         if (retval)
 329                 return retval;
 330
 331         retval = register_filesystem(&fs_type);
 332         if (retval)
 333                 subsystem_unregister(&security_subsys);
 334         return retval;
 335 }
 336
 337 static void __exit securityfs_exit(void)
 338 {
 339         simple_release_fs(&mount, &mount_count);
 340         unregister_filesystem(&fs_type);
 341         subsystem_unregister(&security_subsys);
 342 }
 343
 344 core_initcall(securityfs_init);
 345 module_exit(securityfs_exit);
 346 MODULE_LICENSE("GPL");
 347