security/inode.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  inode.c - securityfs
   4  *
   5  *  Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
   6  *
   7  *  Based on fs/debugfs/inode.c which had the following copyright notice:
   8  *    Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   9  *    Copyright (C) 2004 IBM Inc.
  10  */
  11
  12 /* #define DEBUG */
  13 #include <linux/sysfs.h>
  14 #include <linux/kobject.h>
  15 #include <linux/fs.h>
  16 #include <linux/mount.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/init.h>
  19 #include <linux/namei.h>
  20 #include <linux/security.h>
  21 #include <linux/lsm_hooks.h>
  22 #include <linux/magic.h>
  23
  24 static struct vfsmount *mount;
  25 static int mount_count;
  26
  27 static void securityfs_free_inode(struct inode *inode)
  28 {
  29         if (S_ISLNK(inode->i_mode))
  30                 kfree(inode->i_link);
  31         free_inode_nonrcu(inode);
  32 }
  33
  34 static const struct super_operations securityfs_super_operations = {
  35         .statfs         = simple_statfs,
  36         .free_inode     = securityfs_free_inode,
  37 };
  38
  39 static int fill_super(struct super_block *sb, void *data, int silent)
  40 {
  41         static const struct tree_descr files[] = {{""}};
  42         int error;
  43
  44         error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
  45         if (error)
  46                 return error;
  47
  48         sb->s_op = &securityfs_super_operations;
  49
  50         return 0;
  51 }
  52
  53 static struct dentry *get_sb(struct file_system_type *fs_type,
  54                   int flags, const char *dev_name,
  55                   void *data)
  56 {
  57         return mount_single(fs_type, flags, data, fill_super);
  58 }
  59
  60 static struct file_system_type fs_type = {
  61         .owner =        THIS_MODULE,
  62         .name =         "securityfs",
  63         .mount =        get_sb,
  64         .kill_sb =      kill_litter_super,
  65 };
  66
  67 /**
  68  * securityfs_create_dentry - create a dentry in the securityfs filesystem
  69  *
  70  * @name: a pointer to a string containing the name of the file to create.
  71  * @mode: the permission that the file should have
  72  * @parent: a pointer to the parent dentry for this file.  This should be a
  73  *          directory dentry if set.  If this parameter is %NULL, then the
  74  *          file will be created in the root of the securityfs filesystem.
  75  * @data: a pointer to something that the caller will want to get to later
  76  *        on.  The inode.i_private pointer will point to this value on
  77  *        the open() call.
  78  * @fops: a pointer to a struct file_operations that should be used for
  79  *        this file.
  80  * @iops: a point to a struct of inode_operations that should be used for
  81  *        this file/dir
  82  *
  83  * This is the basic "create a file/dir/symlink" function for
  84  * securityfs.  It allows for a wide range of flexibility in creating
  85  * a file, or a directory (if you want to create a directory, the
  86  * securityfs_create_dir() function is recommended to be used
  87  * instead).
  88  *
  89  * This function returns a pointer to a dentry if it succeeds.  This
  90  * pointer must be passed to the securityfs_remove() function when the
  91  * file is to be removed (no automatic cleanup happens if your module
  92  * is unloaded, you are responsible here).  If an error occurs, the
  93  * function will return the error value (via ERR_PTR).
  94  *
  95  * If securityfs is not enabled in the kernel, the value %-ENODEV is
  96  * returned.
  97  */
  98 static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
  99                                         struct dentry *parent, void *data,
 100                                         const struct file_operations *fops,
 101                                         const struct inode_operations *iops)
 102 {
 103         struct dentry *dentry;
 104         struct inode *dir, *inode;
 105         int error;
 106
 107         if (!(mode & S_IFMT))
 108                 mode = (mode & S_IALLUGO) | S_IFREG;
 109
 110         pr_debug("securityfs: creating file '%s'\n",name);
 111
 112         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 113         if (error)
 114                 return ERR_PTR(error);
 115
 116         if (!parent)
 117                 parent = mount->mnt_root;
 118
 119         dir = d_inode(parent);
 120
 121         inode_lock(dir);
 122         dentry = lookup_one_len(name, parent, strlen(name));
 123         if (IS_ERR(dentry))
 124                 goto out;
 125
 126         if (d_really_is_positive(dentry)) {
 127                 error = -EEXIST;
 128                 goto out1;
 129         }
 130
 131         inode = new_inode(dir->i_sb);
 132         if (!inode) {
 133                 error = -ENOMEM;
 134                 goto out1;
 135         }
 136
 137         inode->i_ino = get_next_ino();
 138         inode->i_mode = mode;
 139         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 140         inode->i_private = data;
 141         if (S_ISDIR(mode)) {
 142                 inode->i_op = &simple_dir_inode_operations;
 143                 inode->i_fop = &simple_dir_operations;
 144                 inc_nlink(inode);
 145                 inc_nlink(dir);
 146         } else if (S_ISLNK(mode)) {
 147                 inode->i_op = iops ? iops : &simple_symlink_inode_operations;
 148                 inode->i_link = data;
 149         } else {
 150                 inode->i_fop = fops;
 151         }
 152         d_instantiate(dentry, inode);
 153         dget(dentry);
 154         inode_unlock(dir);
 155         return dentry;
 156
 157 out1:
 158         dput(dentry);
 159         dentry = ERR_PTR(error);
 160 out:
 161         inode_unlock(dir);
 162         simple_release_fs(&mount, &mount_count);
 163         return dentry;
 164 }
 165
 166 /**
 167  * securityfs_create_file - create a file in the securityfs filesystem
 168  *
 169  * @name: a pointer to a string containing the name of the file to create.
 170  * @mode: the permission that the file should have
 171  * @parent: a pointer to the parent dentry for this file.  This should be a
 172  *          directory dentry if set.  If this parameter is %NULL, then the
 173  *          file will be created in the root of the securityfs filesystem.
 174  * @data: a pointer to something that the caller will want to get to later
 175  *        on.  The inode.i_private pointer will point to this value on
 176  *        the open() call.
 177  * @fops: a pointer to a struct file_operations that should be used for
 178  *        this file.
 179  *
 180  * This function creates a file in securityfs with the given @name.
 181  *
 182  * This function returns a pointer to a dentry if it succeeds.  This
 183  * pointer must be passed to the securityfs_remove() function when the file is
 184  * to be removed (no automatic cleanup happens if your module is unloaded,
 185  * you are responsible here).  If an error occurs, the function will return
 186  * the error value (via ERR_PTR).
 187  *
 188  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 189  * returned.
 190  */
 191 struct dentry *securityfs_create_file(const char *name, umode_t mode,
 192                                       struct dentry *parent, void *data,
 193                                       const struct file_operations *fops)
 194 {
 195         return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
 196 }
 197 EXPORT_SYMBOL_GPL(securityfs_create_file);
 198
 199 /**
 200  * securityfs_create_dir - create a directory in the securityfs filesystem
 201  *
 202  * @name: a pointer to a string containing the name of the directory to
 203  *        create.
 204  * @parent: a pointer to the parent dentry for this file.  This should be a
 205  *          directory dentry if set.  If this parameter is %NULL, then the
 206  *          directory will be created in the root of the securityfs filesystem.
 207  *
 208  * This function creates a directory in securityfs with the given @name.
 209  *
 210  * This function returns a pointer to a dentry if it succeeds.  This
 211  * pointer must be passed to the securityfs_remove() function when the file is
 212  * to be removed (no automatic cleanup happens if your module is unloaded,
 213  * you are responsible here).  If an error occurs, the function will return
 214  * the error value (via ERR_PTR).
 215  *
 216  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 217  * returned.
 218  */
 219 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 220 {
 221         return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL);
 222 }
 223 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 224
 225 /**
 226  * securityfs_create_symlink - create a symlink in the securityfs filesystem
 227  *
 228  * @name: a pointer to a string containing the name of the symlink to
 229  *        create.
 230  * @parent: a pointer to the parent dentry for the symlink.  This should be a
 231  *          directory dentry if set.  If this parameter is %NULL, then the
 232  *          directory will be created in the root of the securityfs filesystem.
 233  * @target: a pointer to a string containing the name of the symlink's target.
 234  *          If this parameter is %NULL, then the @iops parameter needs to be
 235  *          setup to handle .readlink and .get_link inode_operations.
 236  * @iops: a pointer to the struct inode_operations to use for the symlink. If
 237  *        this parameter is %NULL, then the default simple_symlink_inode
 238  *        operations will be used.
 239  *
 240  * This function creates a symlink in securityfs with the given @name.
 241  *
 242  * This function returns a pointer to a dentry if it succeeds.  This
 243  * pointer must be passed to the securityfs_remove() function when the file is
 244  * to be removed (no automatic cleanup happens if your module is unloaded,
 245  * you are responsible here).  If an error occurs, the function will return
 246  * the error value (via ERR_PTR).
 247  *
 248  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 249  * returned.
 250  */
 251 struct dentry *securityfs_create_symlink(const char *name,
 252                                          struct dentry *parent,
 253                                          const char *target,
 254                                          const struct inode_operations *iops)
 255 {
 256         struct dentry *dent;
 257         char *link = NULL;
 258
 259         if (target) {
 260                 link = kstrdup(target, GFP_KERNEL);
 261                 if (!link)
 262                         return ERR_PTR(-ENOMEM);
 263         }
 264         dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
 265                                         link, NULL, iops);
 266         if (IS_ERR(dent))
 267                 kfree(link);
 268
 269         return dent;
 270 }
 271 EXPORT_SYMBOL_GPL(securityfs_create_symlink);
 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 inode *dir;
 289
 290         if (!dentry || IS_ERR(dentry))
 291                 return;
 292
 293         dir = d_inode(dentry->d_parent);
 294         inode_lock(dir);
 295         if (simple_positive(dentry)) {
 296                 if (d_is_dir(dentry))
 297                         simple_rmdir(dir, dentry);
 298                 else
 299                         simple_unlink(dir, dentry);
 300                 dput(dentry);
 301         }
 302         inode_unlock(dir);
 303         simple_release_fs(&mount, &mount_count);
 304 }
 305 EXPORT_SYMBOL_GPL(securityfs_remove);
 306
 307 #ifdef CONFIG_SECURITY
 308 static struct dentry *lsm_dentry;
 309 static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
 310                         loff_t *ppos)
 311 {
 312         return simple_read_from_buffer(buf, count, ppos, lsm_names,
 313                 strlen(lsm_names));
 314 }
 315
 316 static const struct file_operations lsm_ops = {
 317         .read = lsm_read,
 318         .llseek = generic_file_llseek,
 319 };
 320 #endif
 321
 322 static int __init securityfs_init(void)
 323 {
 324         int retval;
 325
 326         retval = sysfs_create_mount_point(kernel_kobj, "security");
 327         if (retval)
 328                 return retval;
 329
 330         retval = register_filesystem(&fs_type);
 331         if (retval) {
 332                 sysfs_remove_mount_point(kernel_kobj, "security");
 333                 return retval;
 334         }
 335 #ifdef CONFIG_SECURITY
 336         lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
 337                                                 &lsm_ops);
 338 #endif
 339         return 0;
 340 }
 341 core_initcall(securityfs_init);