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 inode->i_atime = inode->i_mtime = 155 inode->i_ctime = current_time(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->i_atime = attrs->ia_atime; 164 inode->i_mtime = attrs->ia_mtime; 165 inode->i_ctime = attrs->ia_ctime; 166 } 167 168 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode) 169 { 170 struct kernfs_iattrs *attrs = kn->iattr; 171 172 inode->i_mode = kn->mode; 173 if (attrs) 174 /* 175 * kernfs_node has non-default attributes get them from 176 * persistent copy in kernfs_node. 177 */ 178 set_inode_attr(inode, attrs); 179 180 if (kernfs_type(kn) == KERNFS_DIR) 181 set_nlink(inode, kn->dir.subdirs + 2); 182 } 183 184 int kernfs_iop_getattr(struct mnt_idmap *idmap, 185 const struct path *path, struct kstat *stat, 186 u32 request_mask, unsigned int query_flags) 187 { 188 struct inode *inode = d_inode(path->dentry); 189 struct kernfs_node *kn = inode->i_private; 190 struct kernfs_root *root = kernfs_root(kn); 191 192 down_read(&root->kernfs_iattr_rwsem); 193 kernfs_refresh_inode(kn, inode); 194 generic_fillattr(&nop_mnt_idmap, inode, stat); 195 up_read(&root->kernfs_iattr_rwsem); 196 197 return 0; 198 } 199 200 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) 201 { 202 kernfs_get(kn); 203 inode->i_private = kn; 204 inode->i_mapping->a_ops = &ram_aops; 205 inode->i_op = &kernfs_iops; 206 inode->i_generation = kernfs_gen(kn); 207 208 set_default_inode_attr(inode, kn->mode); 209 kernfs_refresh_inode(kn, inode); 210 211 /* initialize inode according to type */ 212 switch (kernfs_type(kn)) { 213 case KERNFS_DIR: 214 inode->i_op = &kernfs_dir_iops; 215 inode->i_fop = &kernfs_dir_fops; 216 if (kn->flags & KERNFS_EMPTY_DIR) 217 make_empty_dir_inode(inode); 218 break; 219 case KERNFS_FILE: 220 inode->i_size = kn->attr.size; 221 inode->i_fop = &kernfs_file_fops; 222 break; 223 case KERNFS_LINK: 224 inode->i_op = &kernfs_symlink_iops; 225 break; 226 default: 227 BUG(); 228 } 229 230 unlock_new_inode(inode); 231 } 232 233 /** 234 * kernfs_get_inode - get inode for kernfs_node 235 * @sb: super block 236 * @kn: kernfs_node to allocate inode for 237 * 238 * Get inode for @kn. If such inode doesn't exist, a new inode is 239 * allocated and basics are initialized. New inode is returned 240 * locked. 241 * 242 * Locking: 243 * Kernel thread context (may sleep). 244 * 245 * Return: 246 * Pointer to allocated inode on success, %NULL on failure. 247 */ 248 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn) 249 { 250 struct inode *inode; 251 252 inode = iget_locked(sb, kernfs_ino(kn)); 253 if (inode && (inode->i_state & I_NEW)) 254 kernfs_init_inode(kn, inode); 255 256 return inode; 257 } 258 259 /* 260 * The kernfs_node serves as both an inode and a directory entry for 261 * kernfs. To prevent the kernfs inode numbers from being freed 262 * prematurely we take a reference to kernfs_node from the kernfs inode. A 263 * super_operations.evict_inode() implementation is needed to drop that 264 * reference upon inode destruction. 265 */ 266 void kernfs_evict_inode(struct inode *inode) 267 { 268 struct kernfs_node *kn = inode->i_private; 269 270 truncate_inode_pages_final(&inode->i_data); 271 clear_inode(inode); 272 kernfs_put(kn); 273 } 274 275 int kernfs_iop_permission(struct mnt_idmap *idmap, 276 struct inode *inode, int mask) 277 { 278 struct kernfs_node *kn; 279 struct kernfs_root *root; 280 int ret; 281 282 if (mask & MAY_NOT_BLOCK) 283 return -ECHILD; 284 285 kn = inode->i_private; 286 root = kernfs_root(kn); 287 288 down_read(&root->kernfs_iattr_rwsem); 289 kernfs_refresh_inode(kn, inode); 290 ret = generic_permission(&nop_mnt_idmap, inode, mask); 291 up_read(&root->kernfs_iattr_rwsem); 292 293 return ret; 294 } 295 296 int kernfs_xattr_get(struct kernfs_node *kn, const char *name, 297 void *value, size_t size) 298 { 299 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn); 300 if (!attrs) 301 return -ENODATA; 302 303 return simple_xattr_get(&attrs->xattrs, name, value, size); 304 } 305 306 int kernfs_xattr_set(struct kernfs_node *kn, const char *name, 307 const void *value, size_t size, int flags) 308 { 309 struct kernfs_iattrs *attrs = kernfs_iattrs(kn); 310 if (!attrs) 311 return -ENOMEM; 312 313 return simple_xattr_set(&attrs->xattrs, name, value, size, flags, NULL); 314 } 315 316 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler, 317 struct dentry *unused, struct inode *inode, 318 const char *suffix, void *value, size_t size) 319 { 320 const char *name = xattr_full_name(handler, suffix); 321 struct kernfs_node *kn = inode->i_private; 322 323 return kernfs_xattr_get(kn, name, value, size); 324 } 325 326 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler, 327 struct mnt_idmap *idmap, 328 struct dentry *unused, struct inode *inode, 329 const char *suffix, const void *value, 330 size_t size, int flags) 331 { 332 const char *name = xattr_full_name(handler, suffix); 333 struct kernfs_node *kn = inode->i_private; 334 335 return kernfs_xattr_set(kn, name, value, size, flags); 336 } 337 338 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn, 339 const char *full_name, 340 struct simple_xattrs *xattrs, 341 const void *value, size_t size, int flags) 342 { 343 atomic_t *sz = &kn->iattr->user_xattr_size; 344 atomic_t *nr = &kn->iattr->nr_user_xattrs; 345 ssize_t removed_size; 346 int ret; 347 348 if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) { 349 ret = -ENOSPC; 350 goto dec_count_out; 351 } 352 353 if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) { 354 ret = -ENOSPC; 355 goto dec_size_out; 356 } 357 358 ret = simple_xattr_set(xattrs, full_name, value, size, flags, 359 &removed_size); 360 361 if (!ret && removed_size >= 0) 362 size = removed_size; 363 else if (!ret) 364 return 0; 365 dec_size_out: 366 atomic_sub(size, sz); 367 dec_count_out: 368 atomic_dec(nr); 369 return ret; 370 } 371 372 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn, 373 const char *full_name, 374 struct simple_xattrs *xattrs, 375 const void *value, size_t size, int flags) 376 { 377 atomic_t *sz = &kn->iattr->user_xattr_size; 378 atomic_t *nr = &kn->iattr->nr_user_xattrs; 379 ssize_t removed_size; 380 int ret; 381 382 ret = simple_xattr_set(xattrs, full_name, value, size, flags, 383 &removed_size); 384 385 if (removed_size >= 0) { 386 atomic_sub(removed_size, sz); 387 atomic_dec(nr); 388 } 389 390 return ret; 391 } 392 393 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler, 394 struct mnt_idmap *idmap, 395 struct dentry *unused, struct inode *inode, 396 const char *suffix, const void *value, 397 size_t size, int flags) 398 { 399 const char *full_name = xattr_full_name(handler, suffix); 400 struct kernfs_node *kn = inode->i_private; 401 struct kernfs_iattrs *attrs; 402 403 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR)) 404 return -EOPNOTSUPP; 405 406 attrs = kernfs_iattrs(kn); 407 if (!attrs) 408 return -ENOMEM; 409 410 if (value) 411 return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs, 412 value, size, flags); 413 else 414 return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs, 415 value, size, flags); 416 417 } 418 419 static const struct xattr_handler kernfs_trusted_xattr_handler = { 420 .prefix = XATTR_TRUSTED_PREFIX, 421 .get = kernfs_vfs_xattr_get, 422 .set = kernfs_vfs_xattr_set, 423 }; 424 425 static const struct xattr_handler kernfs_security_xattr_handler = { 426 .prefix = XATTR_SECURITY_PREFIX, 427 .get = kernfs_vfs_xattr_get, 428 .set = kernfs_vfs_xattr_set, 429 }; 430 431 static const struct xattr_handler kernfs_user_xattr_handler = { 432 .prefix = XATTR_USER_PREFIX, 433 .get = kernfs_vfs_xattr_get, 434 .set = kernfs_vfs_user_xattr_set, 435 }; 436 437 const struct xattr_handler *kernfs_xattr_handlers[] = { 438 &kernfs_trusted_xattr_handler, 439 &kernfs_security_xattr_handler, 440 &kernfs_user_xattr_handler, 441 NULL 442 }; 443