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