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/fs_context.h>
  17 #include <linux/mount.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/init.h>
  20 #include <linux/namei.h>
  21 #include <linux/security.h>
  22 #include <linux/lsm_hooks.h>
  23 #include <linux/magic.h>
  24
  25 static struct vfsmount *mount;
  26 static int mount_count;
  27
  28 static void securityfs_free_inode(struct inode *inode)
  29 {
  30         if (S_ISLNK(inode->i_mode))
  31                 kfree(inode->i_link);
  32         free_inode_nonrcu(inode);
  33 }
  34
  35 static const struct super_operations securityfs_super_operations = {
  36         .statfs         = simple_statfs,
  37         .free_inode     = securityfs_free_inode,
  38 };
  39
  40 static int securityfs_fill_super(struct super_block *sb, struct fs_context *fc)
  41 {
  42         static const struct tree_descr files[] = {{""}};
  43         int error;
  44
  45         error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
  46         if (error)
  47                 return error;
  48
  49         sb->s_op = &securityfs_super_operations;
  50
  51         return 0;
  52 }
  53
  54 static int securityfs_get_tree(struct fs_context *fc)
  55 {
  56         return get_tree_single(fc, securityfs_fill_super);
  57 }
  58
  59 static const struct fs_context_operations securityfs_context_ops = {
  60         .get_tree       = securityfs_get_tree,
  61 };
  62
  63 static int securityfs_init_fs_context(struct fs_context *fc)
  64 {
  65         fc->ops = &securityfs_context_ops;
  66         return 0;
  67 }
  68
  69 static struct file_system_type fs_type = {
  70         .owner =        THIS_MODULE,
  71         .name =         "securityfs",
  72         .init_fs_context = securityfs_init_fs_context,
  73         .kill_sb =      kill_litter_super,
  74 };
  75
  76 /**
  77  * securityfs_create_dentry - create a dentry in the securityfs filesystem
  78  *
  79  * @name: a pointer to a string containing the name of the file to create.
  80  * @mode: the permission that the file should have
  81  * @parent: a pointer to the parent dentry for this file.  This should be a
  82  *          directory dentry if set.  If this parameter is %NULL, then the
  83  *          file will be created in the root of the securityfs filesystem.
  84  * @data: a pointer to something that the caller will want to get to later
  85  *        on.  The inode.i_private pointer will point to this value on
  86  *        the open() call.
  87  * @fops: a pointer to a struct file_operations that should be used for
  88  *        this file.
  89  * @iops: a point to a struct of inode_operations that should be used for
  90  *        this file/dir
  91  *
  92  * This is the basic "create a file/dir/symlink" function for
  93  * securityfs.  It allows for a wide range of flexibility in creating
  94  * a file, or a directory (if you want to create a directory, the
  95  * securityfs_create_dir() function is recommended to be used
  96  * instead).
  97  *
  98  * This function returns a pointer to a dentry if it succeeds.  This
  99  * pointer must be passed to the securityfs_remove() function when the
 100  * file is to be removed (no automatic cleanup happens if your module
 101  * is unloaded, you are responsible here).  If an error occurs, the
 102  * function will return the error value (via ERR_PTR).
 103  *
 104  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 105  * returned.
 106  */
 107 static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
 108                                         struct dentry *parent, void *data,
 109                                         const struct file_operations *fops,
 110                                         const struct inode_operations *iops)
 111 {
 112         struct dentry *dentry;
 113         struct inode *dir, *inode;
 114         int error;
 115
 116         if (!(mode & S_IFMT))
 117                 mode = (mode & S_IALLUGO) | S_IFREG;
 118
 119         pr_debug("securityfs: creating file '%s'\n",name);
 120
 121         error = simple_pin_fs(&fs_type, &mount, &mount_count);
 122         if (error)
 123                 return ERR_PTR(error);
 124
 125         if (!parent)
 126                 parent = mount->mnt_root;
 127
 128         dir = d_inode(parent);
 129
 130         inode_lock(dir);
 131         dentry = lookup_one_len(name, parent, strlen(name));
 132         if (IS_ERR(dentry))
 133                 goto out;
 134
 135         if (d_really_is_positive(dentry)) {
 136                 error = -EEXIST;
 137                 goto out1;
 138         }
 139
 140         inode = new_inode(dir->i_sb);
 141         if (!inode) {
 142                 error = -ENOMEM;
 143                 goto out1;
 144         }
 145
 146         inode->i_ino = get_next_ino();
 147         inode->i_mode = mode;
 148         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 149         inode->i_private = data;
 150         if (S_ISDIR(mode)) {
 151                 inode->i_op = &simple_dir_inode_operations;
 152                 inode->i_fop = &simple_dir_operations;
 153                 inc_nlink(inode);
 154                 inc_nlink(dir);
 155         } else if (S_ISLNK(mode)) {
 156                 inode->i_op = iops ? iops : &simple_symlink_inode_operations;
 157                 inode->i_link = data;
 158         } else {
 159                 inode->i_fop = fops;
 160         }
 161         d_instantiate(dentry, inode);
 162         dget(dentry);
 163         inode_unlock(dir);
 164         return dentry;
 165
 166 out1:
 167         dput(dentry);
 168         dentry = ERR_PTR(error);
 169 out:
 170         inode_unlock(dir);
 171         simple_release_fs(&mount, &mount_count);
 172         return dentry;
 173 }
 174
 175 /**
 176  * securityfs_create_file - create a file in the securityfs filesystem
 177  *
 178  * @name: a pointer to a string containing the name of the file to create.
 179  * @mode: the permission that the file should have
 180  * @parent: a pointer to the parent dentry for this file.  This should be a
 181  *          directory dentry if set.  If this parameter is %NULL, then the
 182  *          file will be created in the root of the securityfs filesystem.
 183  * @data: a pointer to something that the caller will want to get to later
 184  *        on.  The inode.i_private pointer will point to this value on
 185  *        the open() call.
 186  * @fops: a pointer to a struct file_operations that should be used for
 187  *        this file.
 188  *
 189  * This function creates a file in securityfs with the given @name.
 190  *
 191  * This function returns a pointer to a dentry if it succeeds.  This
 192  * pointer must be passed to the securityfs_remove() function when the file is
 193  * to be removed (no automatic cleanup happens if your module is unloaded,
 194  * you are responsible here).  If an error occurs, the function will return
 195  * the error value (via ERR_PTR).
 196  *
 197  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 198  * returned.
 199  */
 200 struct dentry *securityfs_create_file(const char *name, umode_t mode,
 201                                       struct dentry *parent, void *data,
 202                                       const struct file_operations *fops)
 203 {
 204         return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
 205 }
 206 EXPORT_SYMBOL_GPL(securityfs_create_file);
 207
 208 /**
 209  * securityfs_create_dir - create a directory in the securityfs filesystem
 210  *
 211  * @name: a pointer to a string containing the name of the directory to
 212  *        create.
 213  * @parent: a pointer to the parent dentry for this file.  This should be a
 214  *          directory dentry if set.  If this parameter is %NULL, then the
 215  *          directory will be created in the root of the securityfs filesystem.
 216  *
 217  * This function creates a directory in securityfs with the given @name.
 218  *
 219  * This function returns a pointer to a dentry if it succeeds.  This
 220  * pointer must be passed to the securityfs_remove() function when the file is
 221  * to be removed (no automatic cleanup happens if your module is unloaded,
 222  * you are responsible here).  If an error occurs, the function will return
 223  * the error value (via ERR_PTR).
 224  *
 225  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 226  * returned.
 227  */
 228 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
 229 {
 230         return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL);
 231 }
 232 EXPORT_SYMBOL_GPL(securityfs_create_dir);
 233
 234 /**
 235  * securityfs_create_symlink - create a symlink in the securityfs filesystem
 236  *
 237  * @name: a pointer to a string containing the name of the symlink to
 238  *        create.
 239  * @parent: a pointer to the parent dentry for the symlink.  This should be a
 240  *          directory dentry if set.  If this parameter is %NULL, then the
 241  *          directory will be created in the root of the securityfs filesystem.
 242  * @target: a pointer to a string containing the name of the symlink's target.
 243  *          If this parameter is %NULL, then the @iops parameter needs to be
 244  *          setup to handle .readlink and .get_link inode_operations.
 245  * @iops: a pointer to the struct inode_operations to use for the symlink. If
 246  *        this parameter is %NULL, then the default simple_symlink_inode
 247  *        operations will be used.
 248  *
 249  * This function creates a symlink in securityfs with the given @name.
 250  *
 251  * This function returns a pointer to a dentry if it succeeds.  This
 252  * pointer must be passed to the securityfs_remove() function when the file is
 253  * to be removed (no automatic cleanup happens if your module is unloaded,
 254  * you are responsible here).  If an error occurs, the function will return
 255  * the error value (via ERR_PTR).
 256  *
 257  * If securityfs is not enabled in the kernel, the value %-ENODEV is
 258  * returned.
 259  */
 260 struct dentry *securityfs_create_symlink(const char *name,
 261                                          struct dentry *parent,
 262                                          const char *target,
 263                                          const struct inode_operations *iops)
 264 {
 265         struct dentry *dent;
 266         char *link = NULL;
 267
 268         if (target) {
 269                 link = kstrdup(target, GFP_KERNEL);
 270                 if (!link)
 271                         return ERR_PTR(-ENOMEM);
 272         }
 273         dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
 274                                         link, NULL, iops);
 275         if (IS_ERR(dent))
 276                 kfree(link);
 277
 278         return dent;
 279 }
 280 EXPORT_SYMBOL_GPL(securityfs_create_symlink);
 281
 282 /**
 283  * securityfs_remove - removes a file or directory from the securityfs filesystem
 284  *
 285  * @dentry: a pointer to a the dentry of the file or directory to be removed.
 286  *
 287  * This function removes a file or directory in securityfs that was previously
 288  * created with a call to another securityfs function (like
 289  * securityfs_create_file() or variants thereof.)
 290  *
 291  * This function is required to be called in order for the file to be
 292  * removed. No automatic cleanup of files will happen when a module is
 293  * removed; you are responsible here.
 294  */
 295 void securityfs_remove(struct dentry *dentry)
 296 {
 297         struct inode *dir;
 298
 299         if (!dentry || IS_ERR(dentry))
 300                 return;
 301
 302         dir = d_inode(dentry->d_parent);
 303         inode_lock(dir);
 304         if (simple_positive(dentry)) {
 305                 if (d_is_dir(dentry))
 306                         simple_rmdir(dir, dentry);
 307                 else
 308                         simple_unlink(dir, dentry);
 309                 dput(dentry);
 310         }
 311         inode_unlock(dir);
 312         simple_release_fs(&mount, &mount_count);
 313 }
 314 EXPORT_SYMBOL_GPL(securityfs_remove);
 315
 316 #ifdef CONFIG_SECURITY
 317 static struct dentry *lsm_dentry;
 318 static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
 319                         loff_t *ppos)
 320 {
 321         return simple_read_from_buffer(buf, count, ppos, lsm_names,
 322                 strlen(lsm_names));
 323 }
 324
 325 static const struct file_operations lsm_ops = {
 326         .read = lsm_read,
 327         .llseek = generic_file_llseek,
 328 };
 329 #endif
 330
 331 static int __init securityfs_init(void)
 332 {
 333         int retval;
 334
 335         retval = sysfs_create_mount_point(kernel_kobj, "security");
 336         if (retval)
 337                 return retval;
 338
 339         retval = register_filesystem(&fs_type);
 340         if (retval) {
 341                 sysfs_remove_mount_point(kernel_kobj, "security");
 342                 return retval;
 343         }
 344 #ifdef CONFIG_SECURITY
 345         lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
 346                                                 &lsm_ops);
 347 #endif
 348         return 0;
 349 }
 350 core_initcall(securityfs_init);