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/magic.h>
  24
  25 static struct vfsmount *mount;
  26 static int mount_count;
  27
  28 /*
  29  * TODO:
  30  *   I think I can get rid of these default_file_ops, but not quite sure...
  31  */
  32 static ssize_t default_read_file(struct file *file, char __user *buf,
  33                                  size_t count, loff_t *ppos)
  34 {
  35         return 0;
  36 }
  37
  38 static ssize_t default_write_file(struct file *file, const char __user *buf,
  39                                    size_t count, loff_t *ppos)
  40 {
  41         return count;
  42 }
  43
  44 static int default_open(struct inode *inode, struct file *file)
  45 {
  46         if (inode->i_private)
  47                 file->private_data = inode->i_private;
  48
  49         return 0;
  50 }
  51
  52 static const struct file_operations default_file_ops = {
  53         .read =         default_read_file,
  54         .write =        default_write_file,
  55         .open =         default_open,
  56 };
  57
  58 static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)
  59 {
  60         struct inode *inode = new_inode(sb);
  61
  62         if (inode) {
  63                 inode->i_mode = mode;
  64                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  65                 switch (mode & S_IFMT) {
  66                 default:
  67                         init_special_inode(inode, mode, dev);
  68                         break;
  69                 case S_IFREG:
  70                         inode->i_fop = &default_file_ops;
  71                         break;
  72                 case S_IFDIR:
  73                         inode->i_op = &simple_dir_inode_operations;
  74                         inode->i_fop = &simple_dir_operations;
  75
  76                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
  77                         inc_nlink(inode);
  78                         break;
  79                 }
  80         }
  81         return inode;
  82 }
  83
  84 /* SMP-safe */
  85 static int mknod(struct inode *dir, struct dentry *dentry,
  86                          int mode, dev_t dev)
  87 {
  88         struct inode *inode;
  89         int error = -EPERM;
  90
  91         if (dentry->d_inode)
  92                 return -EEXIST;
  93
  94         inode = get_inode(dir->i_sb, mode, dev);
  95         if (inode) {
  96                 d_instantiate(dentry, inode);
  97                 dget(dentry);
  98                 error = 0;
  99         }
 100         return error;
 101 }
 102
 103 static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
 104 {
 105         int res;
 106
 107         mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
 108         res = mknod(dir, dentry, mode, 0);
 109         if (!res)
 110                 inc_nlink(dir);
 111         return res;
 112 }
 113
 114 static int create(struct inode *dir, struct dentry *dentry, int mode)
 115 {
 116         mode = (mode & S_IALLUGO) | S_IFREG;
 117         return mknod(dir, dentry, mode, 0);
 118 }
 119
 120 static inline int positive(struct dentry *dentry)
 121 {
 122         return dentry->d_inode && !d_unhashed(dentry);
 123 }
 124
 125 static int fill_super(struct super_block *sb, void *data, int silent)
 126 {
 127         static struct tree_descr files[] = {{""}};
 128
 129         return simple_fill_super(sb, SECURITYFS_MAGIC, files);
 130 }
 131
 132 static int get_sb(struct file_system_type *fs_type,
 133                   int flags, const char *dev_name,
 134                   void *data, struct vfsmount *mnt)
 135 {
 136         return get_sb_single(fs_type, flags, data, fill_super, mnt);
 137 }
 138
 139 static struct file_system_type fs_type = {
 140         .owner =        THIS_MODULE,
 141         .name =         "securityfs",
 142         .get_sb =       get_sb,
 143         .kill_sb =      kill_litter_super,
 144 };
 145
 146 static int create_by_name(const char *name, mode_t mode,
 147                           struct dentry *parent,
 148                           struct dentry **dentry)
 149 {
 150         int error = 0;
 151
 152         *dentry = NULL;
 153
 154         /* If the parent is not specified, we create it in the root.
 155          * We need the root dentry to do this, which is in the super
 156          * block. A pointer to that is in the struct vfsmount that we
 157          * have around.
 158          */
 159         if (!parent ) {
 160                 if (mount && mount->mnt_sb) {
 161                         parent = mount->mnt_sb->s_root;
 162                 }
 163         }
 164         if (!parent) {
 165                 pr_debug("securityfs: Ah! can not find a parent!\n");
 166                 return -EFAULT;
 167         }
 168
 169         mutex_lock(&parent->d_inode->i_mutex);
 170         *dentry = lookup_one_len(name, parent, strlen(name));
 171         if (!IS_ERR(dentry)) {
 172                 if ((mode & S_IFMT) == S_IFDIR)
 173                         error = mkdir(parent->d_inode, *dentry, mode);
 174                 else
 175                         error = create(parent->d_inode, *dentry, mode);
 176         } else
 177                 error = PTR_ERR(dentry);
 178         mutex_unlock(&parent->d_inode->i_mutex);
 179
 180         return error;
 181 }
 182
 183 /**
 184  * securityfs_create_file - create a file in the securityfs filesystem
 185  *
 186  * @name: a pointer to a string containing the name of the file to create.
 187  * @mode: the permission that the file should have
 188  * @parent: a pointer to the parent dentry for this file.  This should be a
 189  *          directory dentry if set.  If this parameter is %NULL, then the
 190  *          file will be created in the root of the securityfs filesystem.
 191  * @data: a pointer to something that the caller will want to get to later
 192  *        on.  The inode.i_private pointer will point to this value on
 193  *        the open() call.
 194  * @fops: a pointer to a struct file_operations that should be used for
 195  *        this file.
 196  *
 197  * This is the basic "create a file" function for securityfs.  It allows for a
 198  * wide range of flexibility in creating a file, or a directory (if you
 199  * want to create a directory, the securityfs_create_dir() function is
 200  * recommended to be used instead).
 201  *
 202  * This function returns a pointer to a dentry if it succeeds.  This
 203  * pointer must be passed to the securityfs_remove() function when the file is
 204  * to be removed (no automatic cleanup happens if your module is unloaded,
 205  * you are responsible here).  If an error occurs, the function will return
 206  * the erorr value (via ERR_PTR).
 207  *
 208  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 209  * returned.
 210  */
 211 struct dentry *securityfs_create_file(const char *name, mode_t mode,
 212                                    struct dentry *parent, void *data,
 213                                    const struct file_operations *fops)
 214 {
 215         struct dentry *dentry = NULL;
 216         int error;
 217
 218         pr_debug("securityfs: creating file '%s'\n",name);
 219
 220         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 221         if (error) {
 222                 dentry = ERR_PTR(error);
 223                 goto exit;
 224         }
 225
 226         error = create_by_name(name, mode, parent, &dentry);
 227         if (error) {
 228                 dentry = ERR_PTR(error);
 229                 simple_release_fs(&mount, &mount_count);
 230                 goto exit;
 231         }
 232
 233         if (dentry->d_inode) {
 234                 if (fops)
 235                         dentry->d_inode->i_fop = fops;
 236                 if (data)
 237                         dentry->d_inode->i_private = data;
 238         }
 239 exit:
 240         return dentry;
 241 }
 242 EXPORT_SYMBOL_GPL(securityfs_create_file);
 243
 244 /**
 245  * securityfs_create_dir - create a directory in the securityfs filesystem
 246  *
 247  * @name: a pointer to a string containing the name of the directory to
 248  *        create.
 249  * @parent: a pointer to the parent dentry for this file.  This should be a
 250  *          directory dentry if set.  If this parameter is %NULL, then the
 251  *          directory will be created in the root of the securityfs filesystem.
 252  *
 253  * This function creates a directory in securityfs with the given @name.
 254  *
 255  * This function returns a pointer to a dentry if it succeeds.  This
 256  * pointer must be passed to the securityfs_remove() function when the file is
 257  * to be removed (no automatic cleanup happens if your module is unloaded,
 258  * you are responsible here).  If an error occurs, %NULL will be returned.
 259  *
 260  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 261  * returned.  It is not wise to check for this value, but rather, check for
 262  * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
 263  * code.
 264  */
 265 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 266 {
 267         return securityfs_create_file(name,
 268                                       S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 269                                       parent, NULL, NULL);
 270 }
 271 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 272
 273 /**
 274  * securityfs_remove - removes a file or directory from the securityfs filesystem
 275  *
 276  * @dentry: a pointer to a the dentry of the file or directory to be removed.
 277  *
 278  * This function removes a file or directory in securityfs that was previously
 279  * created with a call to another securityfs function (like
 280  * securityfs_create_file() or variants thereof.)
 281  *
 282  * This function is required to be called in order for the file to be
 283  * removed. No automatic cleanup of files will happen when a module is
 284  * removed; you are responsible here.
 285  */
 286 void securityfs_remove(struct dentry *dentry)
 287 {
 288         struct dentry *parent;
 289
 290         if (!dentry)
 291                 return;
 292
 293         parent = dentry->d_parent;
 294         if (!parent || !parent->d_inode)
 295                 return;
 296
 297         mutex_lock(&parent->d_inode->i_mutex);
 298         if (positive(dentry)) {
 299                 if (dentry->d_inode) {
 300                         if (S_ISDIR(dentry->d_inode->i_mode))
 301                                 simple_rmdir(parent->d_inode, dentry);
 302                         else
 303                                 simple_unlink(parent->d_inode, dentry);
 304                         dput(dentry);
 305                 }
 306         }
 307         mutex_unlock(&parent->d_inode->i_mutex);
 308         simple_release_fs(&mount, &mount_count);
 309 }
 310 EXPORT_SYMBOL_GPL(securityfs_remove);
 311
 312 static struct kobject *security_kobj;
 313
 314 static int __init securityfs_init(void)
 315 {
 316         int retval;
 317
 318         security_kobj = kobject_create_and_add("security", kernel_kobj);
 319         if (!security_kobj)
 320                 return -EINVAL;
 321
 322         retval = register_filesystem(&fs_type);
 323         if (retval)
 324                 kobject_put(security_kobj);
 325         return retval;
 326 }
 327
 328 core_initcall(securityfs_init);
 329 MODULE_LICENSE("GPL");
 330