1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2012 Red Hat, Inc. 4 * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com> 5 */ 6 7 #include <linux/ctype.h> 8 #include <linux/efi.h> 9 #include <linux/fs.h> 10 #include <linux/fs_context.h> 11 #include <linux/fs_parser.h> 12 #include <linux/module.h> 13 #include <linux/pagemap.h> 14 #include <linux/ucs2_string.h> 15 #include <linux/slab.h> 16 #include <linux/magic.h> 17 #include <linux/statfs.h> 18 #include <linux/notifier.h> 19 #include <linux/printk.h> 20 21 #include "internal.h" 22 23 static int efivarfs_ops_notifier(struct notifier_block *nb, unsigned long event, 24 void *data) 25 { 26 struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info, nb); 27 28 switch (event) { 29 case EFIVAR_OPS_RDONLY: 30 sfi->sb->s_flags |= SB_RDONLY; 31 break; 32 case EFIVAR_OPS_RDWR: 33 sfi->sb->s_flags &= ~SB_RDONLY; 34 break; 35 default: 36 return NOTIFY_DONE; 37 } 38 39 return NOTIFY_OK; 40 } 41 42 static struct inode *efivarfs_alloc_inode(struct super_block *sb) 43 { 44 struct efivar_entry *entry = kzalloc(sizeof(*entry), GFP_KERNEL); 45 46 if (!entry) 47 return NULL; 48 49 inode_init_once(&entry->vfs_inode); 50 entry->removed = false; 51 52 return &entry->vfs_inode; 53 } 54 55 static void efivarfs_free_inode(struct inode *inode) 56 { 57 struct efivar_entry *entry = efivar_entry(inode); 58 59 kfree(entry); 60 } 61 62 static int efivarfs_show_options(struct seq_file *m, struct dentry *root) 63 { 64 struct super_block *sb = root->d_sb; 65 struct efivarfs_fs_info *sbi = sb->s_fs_info; 66 struct efivarfs_mount_opts *opts = &sbi->mount_opts; 67 68 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID)) 69 seq_printf(m, ",uid=%u", 70 from_kuid_munged(&init_user_ns, opts->uid)); 71 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID)) 72 seq_printf(m, ",gid=%u", 73 from_kgid_munged(&init_user_ns, opts->gid)); 74 return 0; 75 } 76 77 static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf) 78 { 79 const u32 attr = EFI_VARIABLE_NON_VOLATILE | 80 EFI_VARIABLE_BOOTSERVICE_ACCESS | 81 EFI_VARIABLE_RUNTIME_ACCESS; 82 u64 storage_space, remaining_space, max_variable_size; 83 u64 id = huge_encode_dev(dentry->d_sb->s_dev); 84 efi_status_t status; 85 86 /* Some UEFI firmware does not implement QueryVariableInfo() */ 87 storage_space = remaining_space = 0; 88 if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) { 89 status = efivar_query_variable_info(attr, &storage_space, 90 &remaining_space, 91 &max_variable_size); 92 if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED) 93 pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n", 94 status); 95 } 96 97 /* 98 * This is not a normal filesystem, so no point in pretending it has a block 99 * size; we declare f_bsize to 1, so that we can then report the exact value 100 * sent by EFI QueryVariableInfo in f_blocks and f_bfree 101 */ 102 buf->f_bsize = 1; 103 buf->f_namelen = NAME_MAX; 104 buf->f_blocks = storage_space; 105 buf->f_bfree = remaining_space; 106 buf->f_type = dentry->d_sb->s_magic; 107 buf->f_fsid = u64_to_fsid(id); 108 109 /* 110 * In f_bavail we declare the free space that the kernel will allow writing 111 * when the storage_paranoia x86 quirk is active. To use more, users 112 * should boot the kernel with efi_no_storage_paranoia. 113 */ 114 if (remaining_space > efivar_reserved_space()) 115 buf->f_bavail = remaining_space - efivar_reserved_space(); 116 else 117 buf->f_bavail = 0; 118 119 return 0; 120 } 121 static const struct super_operations efivarfs_ops = { 122 .statfs = efivarfs_statfs, 123 .drop_inode = generic_delete_inode, 124 .alloc_inode = efivarfs_alloc_inode, 125 .free_inode = efivarfs_free_inode, 126 .show_options = efivarfs_show_options, 127 }; 128 129 /* 130 * Compare two efivarfs file names. 131 * 132 * An efivarfs filename is composed of two parts, 133 * 134 * 1. A case-sensitive variable name 135 * 2. A case-insensitive GUID 136 * 137 * So we need to perform a case-sensitive match on part 1 and a 138 * case-insensitive match on part 2. 139 */ 140 static int efivarfs_d_compare(const struct dentry *dentry, 141 unsigned int len, const char *str, 142 const struct qstr *name) 143 { 144 int guid = len - EFI_VARIABLE_GUID_LEN; 145 146 if (name->len != len) 147 return 1; 148 149 /* Case-sensitive compare for the variable name */ 150 if (memcmp(str, name->name, guid)) 151 return 1; 152 153 /* Case-insensitive compare for the GUID */ 154 return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN); 155 } 156 157 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr) 158 { 159 unsigned long hash = init_name_hash(dentry); 160 const unsigned char *s = qstr->name; 161 unsigned int len = qstr->len; 162 163 while (len-- > EFI_VARIABLE_GUID_LEN) 164 hash = partial_name_hash(*s++, hash); 165 166 /* GUID is case-insensitive. */ 167 while (len--) 168 hash = partial_name_hash(tolower(*s++), hash); 169 170 qstr->hash = end_name_hash(hash); 171 return 0; 172 } 173 174 static const struct dentry_operations efivarfs_d_ops = { 175 .d_compare = efivarfs_d_compare, 176 .d_hash = efivarfs_d_hash, 177 .d_delete = always_delete_dentry, 178 }; 179 180 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name) 181 { 182 struct dentry *d; 183 struct qstr q; 184 int err; 185 186 q.name = name; 187 q.len = strlen(name); 188 189 err = efivarfs_d_hash(parent, &q); 190 if (err) 191 return ERR_PTR(err); 192 193 d = d_alloc(parent, &q); 194 if (d) 195 return d; 196 197 return ERR_PTR(-ENOMEM); 198 } 199 200 bool efivarfs_variable_is_present(efi_char16_t *variable_name, 201 efi_guid_t *vendor, void *data) 202 { 203 char *name = efivar_get_utf8name(variable_name, vendor); 204 struct super_block *sb = data; 205 struct dentry *dentry; 206 struct qstr qstr; 207 208 if (!name) 209 /* 210 * If the allocation failed there'll already be an 211 * error in the log (and likely a huge and growing 212 * number of them since they system will be under 213 * extreme memory pressure), so simply assume 214 * collision for safety but don't add to the log 215 * flood. 216 */ 217 return true; 218 219 qstr.name = name; 220 qstr.len = strlen(name); 221 dentry = d_hash_and_lookup(sb->s_root, &qstr); 222 kfree(name); 223 if (!IS_ERR_OR_NULL(dentry)) 224 dput(dentry); 225 226 return dentry != NULL; 227 } 228 229 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor, 230 unsigned long name_size, void *data) 231 { 232 struct super_block *sb = (struct super_block *)data; 233 struct efivar_entry *entry; 234 struct inode *inode = NULL; 235 struct dentry *dentry, *root = sb->s_root; 236 unsigned long size = 0; 237 char *name; 238 int len; 239 int err = -ENOMEM; 240 bool is_removable = false; 241 242 if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID)) 243 return 0; 244 245 name = efivar_get_utf8name(name16, &vendor); 246 if (!name) 247 return err; 248 249 /* length of the variable name itself: remove GUID and separator */ 250 len = strlen(name) - EFI_VARIABLE_GUID_LEN - 1; 251 252 if (efivar_variable_is_removable(vendor, name, len)) 253 is_removable = true; 254 255 inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0, 256 is_removable); 257 if (!inode) 258 goto fail_name; 259 260 entry = efivar_entry(inode); 261 262 memcpy(entry->var.VariableName, name16, name_size); 263 memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t)); 264 265 dentry = efivarfs_alloc_dentry(root, name); 266 if (IS_ERR(dentry)) { 267 err = PTR_ERR(dentry); 268 goto fail_inode; 269 } 270 271 __efivar_entry_get(entry, NULL, &size, NULL); 272 273 /* copied by the above to local storage in the dentry. */ 274 kfree(name); 275 276 inode_lock(inode); 277 inode->i_private = entry; 278 i_size_write(inode, size + sizeof(__u32)); /* attributes + data */ 279 inode_unlock(inode); 280 d_add(dentry, inode); 281 282 return 0; 283 284 fail_inode: 285 iput(inode); 286 fail_name: 287 kfree(name); 288 289 return err; 290 } 291 292 enum { 293 Opt_uid, Opt_gid, 294 }; 295 296 static const struct fs_parameter_spec efivarfs_parameters[] = { 297 fsparam_uid("uid", Opt_uid), 298 fsparam_gid("gid", Opt_gid), 299 {}, 300 }; 301 302 static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param) 303 { 304 struct efivarfs_fs_info *sbi = fc->s_fs_info; 305 struct efivarfs_mount_opts *opts = &sbi->mount_opts; 306 struct fs_parse_result result; 307 int opt; 308 309 opt = fs_parse(fc, efivarfs_parameters, param, &result); 310 if (opt < 0) 311 return opt; 312 313 switch (opt) { 314 case Opt_uid: 315 opts->uid = result.uid; 316 break; 317 case Opt_gid: 318 opts->gid = result.gid; 319 break; 320 default: 321 return -EINVAL; 322 } 323 324 return 0; 325 } 326 327 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc) 328 { 329 struct efivarfs_fs_info *sfi = sb->s_fs_info; 330 struct inode *inode = NULL; 331 struct dentry *root; 332 int err; 333 334 sb->s_maxbytes = MAX_LFS_FILESIZE; 335 sb->s_blocksize = PAGE_SIZE; 336 sb->s_blocksize_bits = PAGE_SHIFT; 337 sb->s_magic = EFIVARFS_MAGIC; 338 sb->s_op = &efivarfs_ops; 339 sb->s_d_op = &efivarfs_d_ops; 340 sb->s_time_gran = 1; 341 342 if (!efivar_supports_writes()) 343 sb->s_flags |= SB_RDONLY; 344 345 inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true); 346 if (!inode) 347 return -ENOMEM; 348 inode->i_op = &efivarfs_dir_inode_operations; 349 350 root = d_make_root(inode); 351 sb->s_root = root; 352 if (!root) 353 return -ENOMEM; 354 355 sfi->sb = sb; 356 sfi->nb.notifier_call = efivarfs_ops_notifier; 357 err = blocking_notifier_chain_register(&efivar_ops_nh, &sfi->nb); 358 if (err) 359 return err; 360 361 return efivar_init(efivarfs_callback, sb); 362 } 363 364 static int efivarfs_get_tree(struct fs_context *fc) 365 { 366 return get_tree_single(fc, efivarfs_fill_super); 367 } 368 369 static int efivarfs_reconfigure(struct fs_context *fc) 370 { 371 if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) { 372 pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n"); 373 return -EINVAL; 374 } 375 376 return 0; 377 } 378 379 static const struct fs_context_operations efivarfs_context_ops = { 380 .get_tree = efivarfs_get_tree, 381 .parse_param = efivarfs_parse_param, 382 .reconfigure = efivarfs_reconfigure, 383 }; 384 385 static int efivarfs_init_fs_context(struct fs_context *fc) 386 { 387 struct efivarfs_fs_info *sfi; 388 389 if (!efivar_is_available()) 390 return -EOPNOTSUPP; 391 392 sfi = kzalloc(sizeof(*sfi), GFP_KERNEL); 393 if (!sfi) 394 return -ENOMEM; 395 396 sfi->mount_opts.uid = GLOBAL_ROOT_UID; 397 sfi->mount_opts.gid = GLOBAL_ROOT_GID; 398 399 fc->s_fs_info = sfi; 400 fc->ops = &efivarfs_context_ops; 401 return 0; 402 } 403 404 static void efivarfs_kill_sb(struct super_block *sb) 405 { 406 struct efivarfs_fs_info *sfi = sb->s_fs_info; 407 408 blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb); 409 kill_litter_super(sb); 410 411 kfree(sfi); 412 } 413 414 static struct file_system_type efivarfs_type = { 415 .owner = THIS_MODULE, 416 .name = "efivarfs", 417 .init_fs_context = efivarfs_init_fs_context, 418 .kill_sb = efivarfs_kill_sb, 419 .parameters = efivarfs_parameters, 420 }; 421 422 static __init int efivarfs_init(void) 423 { 424 return register_filesystem(&efivarfs_type); 425 } 426 427 static __exit void efivarfs_exit(void) 428 { 429 unregister_filesystem(&efivarfs_type); 430 } 431 432 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr"); 433 MODULE_DESCRIPTION("EFI Variable Filesystem"); 434 MODULE_LICENSE("GPL"); 435 MODULE_ALIAS_FS("efivarfs"); 436 437 module_init(efivarfs_init); 438 module_exit(efivarfs_exit); 439