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 int __securityfs_setup_d_inode(struct inode *dir, struct dentry *dentry,
  55                                umode_t mode, void *data,
  56                                const struct file_operations *fops,
  57                                const struct inode_operations *iops)
  58 {
  59         bool is_dir = S_ISDIR(mode);
  60         struct inode *inode = new_inode(dir->i_sb);
  61         if (!inode)
  62                 return -ENOMEM;
  63
  64         inode->i_ino = get_next_ino();
  65         inode->i_mode = mode;
  66         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  67         inode->i_private = data;
  68         if (is_dir) {
  69                 inode->i_op = iops ? iops : &simple_dir_inode_operations;
  70                 inode->i_fop = &simple_dir_operations;
  71                 inc_nlink(inode);
  72                 inc_nlink(dir);
  73         } else {
  74                 inode->i_fop = fops;
  75         }
  76         d_instantiate(dentry, inode);
  77         dget(dentry);
  78
  79         return 0;
  80 }
  81 EXPORT_SYMBOL_GPL(__securityfs_setup_d_inode);
  82
  83 /**
  84  * securityfs_create_dentry - create a file/dir in the securityfs filesystem
  85  *
  86  * @name: a pointer to a string containing the name of the file to create.
  87  * @mode: the permission that the file should have
  88  * @parent: a pointer to the parent dentry for this file.  This should be a
  89  *          directory dentry if set.  If this parameter is %NULL, then the
  90  *          file will be created in the root of the securityfs filesystem.
  91  * @data: a pointer to something that the caller will want to get to later
  92  *        on.  The inode.i_private pointer will point to this value on
  93  *        the open() call.
  94  * @fops: a pointer to a struct file_operations that should be used for
  95  *        this file.
  96  * @iops: a point to a struct of inode_operations that should be used for
  97  *        this file/dir
  98  *
  99  * This is the basic "create a xxx" function for securityfs.  It allows for a
 100  * wide range of flexibility in creating a file, or a directory (if you
 101  * want to create a directory, the securityfs_create_dir() function is
 102  * recommended to be used instead).
 103  *
 104  * This function returns a pointer to a dentry if it succeeds.  This
 105  * pointer must be passed to the securityfs_remove() function when the file is
 106  * to be removed (no automatic cleanup happens if your module is unloaded,
 107  * you are responsible here).  If an error occurs, the function will return
 108  * the error value (via ERR_PTR).
 109  *
 110  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 111  * returned.
 112  */
 113 struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
 114                                         struct dentry *parent, void *data,
 115                                         const struct file_operations *fops,
 116                                         const struct inode_operations *iops)
 117 {
 118         struct dentry *dentry;
 119         int is_dir = S_ISDIR(mode);
 120         struct inode *dir;
 121         int error;
 122
 123         if (!is_dir) {
 124                 BUG_ON(!fops);
 125                 mode = (mode & S_IALLUGO) | S_IFREG;
 126         }
 127
 128         pr_debug("securityfs: creating file '%s'\n",name);
 129
 130         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 131         if (error)
 132                 return ERR_PTR(error);
 133
 134         if (!parent)
 135                 parent = mount->mnt_root;
 136
 137         dir = d_inode(parent);
 138
 139         inode_lock(dir);
 140         dentry = lookup_one_len(name, parent, strlen(name));
 141         if (IS_ERR(dentry))
 142                 goto out;
 143
 144         if (d_really_is_positive(dentry)) {
 145                 error = -EEXIST;
 146                 goto out1;
 147         }
 148
 149         error = __securityfs_setup_d_inode(dir, dentry, mode, data, fops, iops);
 150         if (error)
 151                 goto out1;
 152         inode_unlock(dir);
 153         return dentry;
 154
 155 out1:
 156         dput(dentry);
 157         dentry = ERR_PTR(error);
 158 out:
 159         inode_unlock(dir);
 160         simple_release_fs(&mount, &mount_count);
 161         return dentry;
 162 }
 163 EXPORT_SYMBOL_GPL(securityfs_create_dentry);
 164
 165 /**
 166  * securityfs_create_file - create a file in the securityfs filesystem
 167  *
 168  * @name: a pointer to a string containing the name of the file to create.
 169  * @mode: the permission that the file should have
 170  * @parent: a pointer to the parent dentry for this file.  This should be a
 171  *          directory dentry if set.  If this parameter is %NULL, then the
 172  *          file will be created in the root of the securityfs filesystem.
 173  * @data: a pointer to something that the caller will want to get to later
 174  *        on.  The inode.i_private pointer will point to this value on
 175  *        the open() call.
 176  * @fops: a pointer to a struct file_operations that should be used for
 177  *        this file.
 178  *
 179  * This function creates a file in securityfs with the given @name.
 180  *
 181  * This function returns a pointer to a dentry if it succeeds.  This
 182  * pointer must be passed to the securityfs_remove() function when the file is
 183  * to be removed (no automatic cleanup happens if your module is unloaded,
 184  * you are responsible here).  If an error occurs, the function will return
 185  * the error value (via ERR_PTR).
 186  *
 187  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 188  * returned.
 189  */
 190 struct dentry *securityfs_create_file(const char *name, umode_t mode,
 191                                      struct dentry *parent, void *data,
 192                                      const struct file_operations *fops)
 193 {
 194         return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
 195 }
 196 EXPORT_SYMBOL_GPL(securityfs_create_file);
 197
 198 /**
 199  * securityfs_create_dir - create a directory in the securityfs filesystem
 200  *
 201  * @name: a pointer to a string containing the name of the directory to
 202  *        create.
 203  * @parent: a pointer to the parent dentry for this file.  This should be a
 204  *          directory dentry if set.  If this parameter is %NULL, then the
 205  *          directory will be created in the root of the securityfs filesystem.
 206  *
 207  * This function creates a directory in securityfs with the given @name.
 208  *
 209  * This function returns a pointer to a dentry if it succeeds.  This
 210  * pointer must be passed to the securityfs_remove() function when the file is
 211  * to be removed (no automatic cleanup happens if your module is unloaded,
 212  * you are responsible here).  If an error occurs, the function will return
 213  * the error value (via ERR_PTR).
 214  *
 215  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 216  * returned.
 217  */
 218 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 219 {
 220         return securityfs_create_file(name,
 221                                       S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 222                                       parent, NULL, NULL);
 223 }
 224 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 225
 226 /**
 227  * securityfs_remove - removes a file or directory from the securityfs filesystem
 228  *
 229  * @dentry: a pointer to a the dentry of the file or directory to be removed.
 230  *
 231  * This function removes a file or directory in securityfs that was previously
 232  * created with a call to another securityfs function (like
 233  * securityfs_create_file() or variants thereof.)
 234  *
 235  * This function is required to be called in order for the file to be
 236  * removed. No automatic cleanup of files will happen when a module is
 237  * removed; you are responsible here.
 238  */
 239 void securityfs_remove(struct dentry *dentry)
 240 {
 241         struct inode *dir;
 242
 243         if (!dentry || IS_ERR(dentry))
 244                 return;
 245
 246         dir = d_inode(dentry->d_parent);
 247         inode_lock(dir);
 248         if (simple_positive(dentry)) {
 249                 if (d_is_dir(dentry))
 250                         simple_rmdir(dir, dentry);
 251                 else
 252                         simple_unlink(dir, dentry);
 253                 dput(dentry);
 254         }
 255         inode_unlock(dir);
 256         simple_release_fs(&mount, &mount_count);
 257 }
 258 EXPORT_SYMBOL_GPL(securityfs_remove);
 259
 260 static int __init securityfs_init(void)
 261 {
 262         int retval;
 263
 264         retval = sysfs_create_mount_point(kernel_kobj, "security");
 265         if (retval)
 266                 return retval;
 267
 268         retval = register_filesystem(&fs_type);
 269         if (retval)
 270                 sysfs_remove_mount_point(kernel_kobj, "security");
 271         return retval;
 272 }
 273
 274 core_initcall(securityfs_init);
 275 MODULE_LICENSE("GPL");
 276