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 static int fill_super(struct super_block *sb, void *data, int silent)
  29 {
  30         static struct tree_descr files[] = {{""}};
  31
  32         return simple_fill_super(sb, SECURITYFS_MAGIC, files);
  33 }
  34
  35 static struct dentry *get_sb(struct file_system_type *fs_type,
  36                   int flags, const char *dev_name,
  37                   void *data)
  38 {
  39         return mount_single(fs_type, flags, data, fill_super);
  40 }
  41
  42 static struct file_system_type fs_type = {
  43         .owner =        THIS_MODULE,
  44         .name =         "securityfs",
  45         .mount =        get_sb,
  46         .kill_sb =      kill_litter_super,
  47 };
  48
  49 int securityfs_pin_fs(void)
  50 {
  51         return simple_pin_fs(&fs_type, &mount, &mount_count);
  52 }
  53
  54 void securityfs_release_fs(void)
  55 {
  56         simple_release_fs(&mount, &mount_count);
  57 }
  58
  59 int __securityfs_setup_d_inode(struct inode *dir, struct dentry *dentry,
  60                                umode_t mode, void *data,
  61                                const struct file_operations *fops,
  62                                const struct inode_operations *iops)
  63 {
  64         bool is_dir = S_ISDIR(mode);
  65         struct inode *inode = new_inode(dir->i_sb);
  66         if (!inode)
  67                 return -ENOMEM;
  68
  69         inode->i_ino = get_next_ino();
  70         inode->i_mode = mode;
  71         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  72         inode->i_private = data;
  73         if (is_dir) {
  74                 inode->i_op = iops ? iops : &simple_dir_inode_operations;
  75                 inode->i_fop = &simple_dir_operations;
  76                 inc_nlink(inode);
  77                 inc_nlink(dir);
  78         } else {
  79                 inode->i_fop = fops;
  80         }
  81         d_instantiate(dentry, inode);
  82         dget(dentry);
  83
  84         return 0;
  85 }
  86 EXPORT_SYMBOL_GPL(__securityfs_setup_d_inode);
  87
  88 /**
  89  * securityfs_create_dentry - create a file/dir in the securityfs filesystem
  90  *
  91  * @name: a pointer to a string containing the name of the file to create.
  92  * @mode: the permission that the file should have
  93  * @parent: a pointer to the parent dentry for this file.  This should be a
  94  *          directory dentry if set.  If this parameter is %NULL, then the
  95  *          file will be created in the root of the securityfs filesystem.
  96  * @data: a pointer to something that the caller will want to get to later
  97  *        on.  The inode.i_private pointer will point to this value on
  98  *        the open() call.
  99  * @fops: a pointer to a struct file_operations that should be used for
 100  *        this file.
 101  * @iops: a point to a struct of inode_operations that should be used for
 102  *        this file/dir
 103  *
 104  * This is the basic "create a xxx" function for securityfs.  It allows for a
 105  * wide range of flexibility in creating a file, or a directory (if you
 106  * want to create a directory, the securityfs_create_dir() function is
 107  * recommended to be used instead).
 108  *
 109  * This function returns a pointer to a dentry if it succeeds.  This
 110  * pointer must be passed to the securityfs_remove() function when the file is
 111  * to be removed (no automatic cleanup happens if your module is unloaded,
 112  * you are responsible here).  If an error occurs, the function will return
 113  * the error value (via ERR_PTR).
 114  *
 115  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 116  * returned.
 117  */
 118 struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
 119                                         struct dentry *parent, void *data,
 120                                         const struct file_operations *fops,
 121                                         const struct inode_operations *iops)
 122 {
 123         struct dentry *dentry;
 124         int is_dir = S_ISDIR(mode);
 125         struct inode *dir;
 126         int error;
 127
 128         if (!is_dir) {
 129                 BUG_ON(!fops);
 130                 mode = (mode & S_IALLUGO) | S_IFREG;
 131         }
 132
 133         pr_debug("securityfs: creating file '%s'\n",name);
 134
 135         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 136         if (error)
 137                 return ERR_PTR(error);
 138
 139         if (!parent)
 140                 parent = mount->mnt_root;
 141
 142         dir = d_inode(parent);
 143
 144         inode_lock(dir);
 145         dentry = lookup_one_len(name, parent, strlen(name));
 146         if (IS_ERR(dentry))
 147                 goto out;
 148
 149         if (d_really_is_positive(dentry)) {
 150                 error = -EEXIST;
 151                 goto out1;
 152         }
 153
 154         error = __securityfs_setup_d_inode(dir, dentry, mode, data, fops, iops);
 155         if (error)
 156                 goto out1;
 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 EXPORT_SYMBOL_GPL(securityfs_create_dentry);
 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,
 226                                       S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 227                                       parent, NULL, NULL);
 228 }
 229 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 230
 231 /**
 232  * securityfs_remove - removes a file or directory from the securityfs filesystem
 233  *
 234  * @dentry: a pointer to a the dentry of the file or directory to be removed.
 235  *
 236  * This function removes a file or directory in securityfs that was previously
 237  * created with a call to another securityfs function (like
 238  * securityfs_create_file() or variants thereof.)
 239  *
 240  * This function is required to be called in order for the file to be
 241  * removed. No automatic cleanup of files will happen when a module is
 242  * removed; you are responsible here.
 243  */
 244 void securityfs_remove(struct dentry *dentry)
 245 {
 246         struct inode *dir;
 247
 248         if (!dentry || IS_ERR(dentry))
 249                 return;
 250
 251         dir = d_inode(dentry->d_parent);
 252         inode_lock(dir);
 253         if (simple_positive(dentry)) {
 254                 if (d_is_dir(dentry))
 255                         simple_rmdir(dir, dentry);
 256                 else
 257                         simple_unlink(dir, dentry);
 258                 dput(dentry);
 259         }
 260         inode_unlock(dir);
 261         simple_release_fs(&mount, &mount_count);
 262 }
 263 EXPORT_SYMBOL_GPL(securityfs_remove);
 264
 265 static int __init securityfs_init(void)
 266 {
 267         int retval;
 268
 269         retval = sysfs_create_mount_point(kernel_kobj, "security");
 270         if (retval)
 271                 return retval;
 272
 273         retval = register_filesystem(&fs_type);
 274         if (retval)
 275                 sysfs_remove_mount_point(kernel_kobj, "security");
 276         return retval;
 277 }
 278
 279 core_initcall(securityfs_init);
 280 MODULE_LICENSE("GPL");
 281