| 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); |