1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * fs/kernfs/inode.c - kernfs inode implementation 4 * 5 * Copyright (c) 2001-3 Patrick Mochel 6 * Copyright (c) 2007 SUSE Linux Products GmbH 7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org> 8 */ 9 10 #include <linux/pagemap.h> 11 #include <linux/backing-dev.h> 12 #include <linux/capability.h> 13 #include <linux/errno.h> 14 #include <linux/slab.h> 15 #include <linux/xattr.h> 16 #include <linux/security.h> 17 18 #include "kernfs-internal.h" 19 20 static const struct inode_operations kernfs_iops = { 21 .permission = kernfs_iop_permission, 22 .setattr = kernfs_iop_setattr, 23 .getattr = kernfs_iop_getattr, 24 .listxattr = kernfs_iop_listxattr, 25 }; 26 27 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, bool alloc) 28 { 29 struct kernfs_iattrs *ret __free(kfree) = NULL; 30 struct kernfs_iattrs *attr; 31 32 attr = READ_ONCE(kn->iattr); 33 if (attr || !alloc) 34 return attr; 35 36 ret = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL); 37 if (!ret) 38 return NULL; 39 40 /* assign default attributes */ 41 ret->ia_uid = GLOBAL_ROOT_UID; 42 ret->ia_gid = GLOBAL_ROOT_GID; 43 44 ktime_get_real_ts64(&ret->ia_atime); 45 ret->ia_mtime = ret->ia_atime; 46 ret->ia_ctime = ret->ia_atime; 47 48 simple_xattrs_init(&ret->xattrs); 49 atomic_set(&ret->nr_user_xattrs, 0); 50 atomic_set(&ret->user_xattr_size, 0); 51 52 /* If someone raced us, recognize it. */ 53 if (!try_cmpxchg(&kn->iattr, &attr, ret)) 54 return READ_ONCE(kn->iattr); 55 56 return no_free_ptr(ret); 57 } 58 59 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn) 60 { 61 return __kernfs_iattrs(kn, true); 62 } 63 64 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn) 65 { 66 return __kernfs_iattrs(kn, false); 67 } 68 69 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr) 70 { 71 struct kernfs_iattrs *attrs; 72 unsigned int ia_valid = iattr->ia_valid; 73 74 attrs = kernfs_iattrs(kn); 75 if (!attrs) 76 return -ENOMEM; 77 78 if (ia_valid & ATTR_UID) 79 attrs->ia_uid = iattr->ia_uid; 80 if (ia_valid & ATTR_GID) 81 attrs->ia_gid = iattr->ia_gid; 82 if (ia_valid & ATTR_ATIME) 83 attrs->ia_atime = iattr->ia_atime; 84 if (ia_valid & ATTR_MTIME) 85 attrs->ia_mtime = iattr->ia_mtime; 86 if (ia_valid & ATTR_CTIME) 87 attrs->ia_ctime = iattr->ia_ctime; 88 if (ia_valid & ATTR_MODE) 89 kn->mode = iattr->ia_mode; 90 return 0; 91 } 92 93 /** 94 * kernfs_setattr - set iattr on a node 95 * @kn: target node 96 * @iattr: iattr to set 97 * 98 * Return: %0 on success, -errno on failure. 99 */ 100 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr) 101 { 102 int ret; 103 struct kernfs_root *root = kernfs_root(kn); 104 105 down_write(&root->kernfs_iattr_rwsem); 106 ret = __kernfs_setattr(kn, iattr); 107 up_write(&root->kernfs_iattr_rwsem); 108 return ret; 109 } 110 111 int kernfs_iop_setattr(struct mnt_idmap *idmap, struct dentry *dentry, 112 struct iattr *iattr) 113 { 114 struct inode *inode = d_inode(dentry); 115 struct kernfs_node *kn = inode->i_private; 116 struct kernfs_root *root; 117 int error; 118 119 if (!kn) 120 return -EINVAL; 121 122 root = kernfs_root(kn); 123 down_write(&root->kernfs_iattr_rwsem); 124 error = setattr_prepare(&nop_mnt_idmap, dentry, iattr); 125 if (error) 126 goto out; 127 128 error = __kernfs_setattr(kn, iattr); 129 if (error) 130 goto out; 131 132 /* this ignores size changes */ 133 setattr_copy(&nop_mnt_idmap, inode, iattr); 134 135 out: 136 up_write(&root->kernfs_iattr_rwsem); 137 return error; 138 } 139 140 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size) 141 { 142 struct kernfs_node *kn = kernfs_dentry_node(dentry); 143 struct kernfs_iattrs *attrs; 144 145 attrs = kernfs_iattrs_noalloc(kn); 146 if (!attrs) 147 return -ENODATA; 148 149 return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size); 150 } 151 152 static inline void set_default_inode_attr(struct inode *inode, umode_t mode) 153 { 154 inode->i_mode = mode; 155 simple_inode_init_ts(inode); 156 } 157 158 static inline void set_inode_attr(struct inode *inode, 159 struct kernfs_iattrs *attrs) 160 { 161 inode->i_uid = attrs->ia_uid; 162 inode->i_gid = attrs->ia_gid; 163 inode_set_atime_to_ts(inode, attrs->ia_atime); 164 inode_set_mtime_to_ts(inode, attrs->ia_mtime); 165 inode_set_ctime_to_ts(inode, attrs->ia_ctime); 166 } 167 168 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode) 169 { 170 struct kernfs_iattrs *attrs; 171 172 inode->i_mode = kn->mode; 173 attrs = kernfs_iattrs_noalloc(kn); 174 if (attrs) 175 /* 176 * kernfs_node has non-default attributes get them from 177 * persistent copy in kernfs_node. 178 */ 179 set_inode_attr(inode, attrs); 180 181 if (kernfs_type(kn) == KERNFS_DIR) 182 set_nlink(inode, kn->dir.subdirs + 2); 183 } 184 185 int kernfs_iop_getattr(struct mnt_idmap *idmap, 186 const struct path *path, struct kstat *stat, 187 u32 request_mask, unsigned int query_flags) 188 { 189 struct inode *inode = d_inode(path->dentry); 190 struct kernfs_node *kn = inode->i_private; 191 struct kernfs_root *root = kernfs_root(kn); 192 193 down_read(&root->kernfs_iattr_rwsem); 194 kernfs_refresh_inode(kn, inode); 195 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); 196 up_read(&root->kernfs_iattr_rwsem); 197 198 return 0; 199 } 200 201 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) 202 { 203 kernfs_get(kn); 204 inode->i_private = kn; 205 inode->i_mapping->a_ops = &ram_aops; 206 inode->i_op = &kernfs_iops; 207 inode->i_generation = kernfs_gen(kn); 208 209 set_default_inode_attr(inode, kn->mode); 210 kernfs_refresh_inode(kn, inode); 211 212 /* initialize inode according to type */ 213 switch (kernfs_type(kn)) { 214 case KERNFS_DIR: 215 inode->i_op = &kernfs_dir_iops; 216 inode->i_fop = &kernfs_dir_fops; 217 if (kn->flags & KERNFS_EMPTY_DIR) 218 make_empty_dir_inode(inode); 219 break; 220 case KERNFS_FILE: 221 inode->i_size = kn->attr.size; 222 inode->i_fop = &kernfs_file_fops; 223 break; 224 case KERNFS_LINK: 225 inode->i_op = &kernfs_symlink_iops; 226 break; 227 default: 228 BUG(); 229 } 230 231 unlock_new_inode(inode); 232 } 233 234 /** 235 * kernfs_get_inode - get inode for kernfs_node 236 * @sb: super block 237 * @kn: kernfs_node to allocate inode for 238 * 239 * Get inode for @kn. If such inode doesn't exist, a new inode is 240 * allocated and basics are initialized. New inode is returned 241 * locked. 242 * 243 * Locking: 244 * Kernel thread context (may sleep). 245 * 246 * Return: 247 * Pointer to allocated inode on success, %NULL on failure. 248 */ 249 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn) 250 { 251 struct inode *inode; 252 253 inode = iget_locked(sb, kernfs_ino(kn)); 254 if (inode && (inode->i_state & I_NEW)) 255 kernfs_init_inode(kn, inode); 256 257 return inode; 258 } 259 260 /* 261 * The kernfs_node serves as both an inode and a directory entry for 262 * kernfs. To prevent the kernfs inode numbers from being freed 263 * prematurely we take a reference to kernfs_node from the kernfs inode. A 264 * super_operations.evict_inode() implementation is needed to drop that 265 * reference upon inode destruction. 266 */ 267 void kernfs_evict_inode(struct inode *inode) 268 { 269 struct kernfs_node *kn = inode->i_private; 270 271 truncate_inode_pages_final(&inode->i_data); 272 clear_inode(inode); 273 kernfs_put(kn); 274 } 275 276 int kernfs_iop_permission(struct mnt_idmap *idmap, 277 struct inode *inode, int mask) 278 { 279 struct kernfs_node *kn; 280 struct kernfs_root *root; 281 int ret; 282 283 if (mask & MAY_NOT_BLOCK) 284 return -ECHILD; 285 286 kn = inode->i_private; 287 root = kernfs_root(kn); 288 289 down_read(&root->kernfs_iattr_rwsem); 290 kernfs_refresh_inode(kn, inode); 291 ret = generic_permission(&nop_mnt_idmap, inode, mask); 292 up_read(&root->kernfs_iattr_rwsem); 293 294 return ret; 295 } 296 297 int kernfs_xattr_get(struct kernfs_node *kn, const char *name, 298 void *value, size_t size) 299 { 300 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn); 301 if (!attrs) 302 return -ENODATA; 303 304 return simple_xattr_get(&attrs->xattrs, name, value, size); 305 } 306 307 int kernfs_xattr_set(struct kernfs_node *kn, const char *name, 308 const void *value, size_t size, int flags) 309 { 310 struct simple_xattr *old_xattr; 311 struct kernfs_iattrs *attrs; 312 313 attrs = kernfs_iattrs(kn); 314 if (!attrs) 315 return -ENOMEM; 316 317 old_xattr = simple_xattr_set(&attrs->xattrs, name, value, size, flags); 318 if (IS_ERR(old_xattr)) 319 return PTR_ERR(old_xattr); 320 321 simple_xattr_free(old_xattr); 322 return 0; 323 } 324 325 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler, 326 struct dentry *unused, struct inode *inode, 327 const char *suffix, void *value, size_t size) 328 { 329 const char *name = xattr_full_name(handler, suffix); 330 struct kernfs_node *kn = inode->i_private; 331 332 return kernfs_xattr_get(kn, name, value, size); 333 } 334 335 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler, 336 struct mnt_idmap *idmap, 337 struct dentry *unused, struct inode *inode, 338 const char *suffix, const void *value, 339 size_t size, int flags) 340 { 341 const char *name = xattr_full_name(handler, suffix); 342 struct kernfs_node *kn = inode->i_private; 343 344 return kernfs_xattr_set(kn, name, value, size, flags); 345 } 346 347 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn, 348 const char *full_name, 349 struct simple_xattrs *xattrs, 350 const void *value, size_t size, int flags) 351 { 352 struct kernfs_iattrs *attr = kernfs_iattrs_noalloc(kn); 353 atomic_t *sz = &attr->user_xattr_size; 354 atomic_t *nr = &attr->nr_user_xattrs; 355 struct simple_xattr *old_xattr; 356 int ret; 357 358 if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) { 359 ret = -ENOSPC; 360 goto dec_count_out; 361 } 362 363 if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) { 364 ret = -ENOSPC; 365 goto dec_size_out; 366 } 367 368 old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags); 369 if (!old_xattr) 370 return 0; 371 372 if (IS_ERR(old_xattr)) { 373 ret = PTR_ERR(old_xattr); 374 goto dec_size_out; 375 } 376 377 ret = 0; 378 size = old_xattr->size; 379 simple_xattr_free(old_xattr); 380 dec_size_out: 381 atomic_sub(size, sz); 382 dec_count_out: 383 atomic_dec(nr); 384 return ret; 385 } 386 387 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn, 388 const char *full_name, 389 struct simple_xattrs *xattrs, 390 const void *value, size_t size, int flags) 391 { 392 struct kernfs_iattrs *attr = kernfs_iattrs_noalloc(kn); 393 atomic_t *sz = &attr->user_xattr_size; 394 atomic_t *nr = &attr->nr_user_xattrs; 395 struct simple_xattr *old_xattr; 396 397 old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags); 398 if (!old_xattr) 399 return 0; 400 401 if (IS_ERR(old_xattr)) 402 return PTR_ERR(old_xattr); 403 404 atomic_sub(old_xattr->size, sz); 405 atomic_dec(nr); 406 simple_xattr_free(old_xattr); 407 return 0; 408 } 409 410 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler, 411 struct mnt_idmap *idmap, 412 struct dentry *unused, struct inode *inode, 413 const char *suffix, const void *value, 414 size_t size, int flags) 415 { 416 const char *full_name = xattr_full_name(handler, suffix); 417 struct kernfs_node *kn = inode->i_private; 418 struct kernfs_iattrs *attrs; 419 420 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR)) 421 return -EOPNOTSUPP; 422 423 attrs = kernfs_iattrs(kn); 424 if (!attrs) 425 return -ENOMEM; 426 427 if (value) 428 return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs, 429 value, size, flags); 430 else 431 return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs, 432 value, size, flags); 433 434 } 435 436 static const struct xattr_handler kernfs_trusted_xattr_handler = { 437 .prefix = XATTR_TRUSTED_PREFIX, 438 .get = kernfs_vfs_xattr_get, 439 .set = kernfs_vfs_xattr_set, 440 }; 441 442 static const struct xattr_handler kernfs_security_xattr_handler = { 443 .prefix = XATTR_SECURITY_PREFIX, 444 .get = kernfs_vfs_xattr_get, 445 .set = kernfs_vfs_xattr_set, 446 }; 447 448 static const struct xattr_handler kernfs_user_xattr_handler = { 449 .prefix = XATTR_USER_PREFIX, 450 .get = kernfs_vfs_xattr_get, 451 .set = kernfs_vfs_user_xattr_set, 452 }; 453 454 const struct xattr_handler * const kernfs_xattr_handlers[] = { 455 &kernfs_trusted_xattr_handler, 456 &kernfs_security_xattr_handler, 457 &kernfs_user_xattr_handler, 458 NULL 459 }; 460