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 INIT_LIST_HEAD_RCU(&ret->xattrs); 41 /* assign default attributes */ 42 ret->ia_uid = GLOBAL_ROOT_UID; 43 ret->ia_gid = GLOBAL_ROOT_GID; 44 45 ktime_get_real_ts64(&ret->ia_atime); 46 ret->ia_mtime = ret->ia_atime; 47 ret->ia_ctime = ret->ia_atime; 48 49 simple_xattr_limits_init(&ret->xattr_limits); 50 51 /* If someone raced us, recognize it. */ 52 if (!try_cmpxchg(&kn->iattr, &attr, ret)) 53 return READ_ONCE(kn->iattr); 54 55 return no_free_ptr(ret); 56 } 57 58 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn) 59 { 60 return __kernfs_iattrs(kn, true); 61 } 62 63 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn) 64 { 65 return __kernfs_iattrs(kn, false); 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; 170 171 inode->i_mode = kn->mode; 172 attrs = kernfs_iattrs_noalloc(kn); 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 && !(kn->flags & KERNFS_REMOVING)) 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, request_mask, 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_state_read_once(inode) & 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 struct simple_xattr_cache *cache = &kernfs_root(kn)->xa_cache; 301 302 if (!attrs) 303 return -ENODATA; 304 305 return simple_xattr_get(cache, &attrs->xattrs, name, value, size); 306 } 307 308 int kernfs_xattr_set(struct kernfs_node *kn, const char *name, 309 const void *value, size_t size, int flags) 310 { 311 struct simple_xattr *old_xattr; 312 struct kernfs_iattrs *attrs; 313 struct simple_xattr_cache *cache = &kernfs_root(kn)->xa_cache; 314 315 attrs = kernfs_iattrs(kn); 316 if (!attrs) 317 return -ENOMEM; 318 319 /* 320 * Protect xattr modifications with the hashed per-node mutex. 321 * Multiple superblocks (with different namespaces) can share the same 322 * kernfs_node, so inode locking alone is insufficient. The hashed mutex 323 * ensures serialization of concurrent xattr operations on the same node, 324 * including the lazy allocation of the xattrs structure itself. 325 */ 326 CLASS(kernfs_node_lock, lock)(kn); 327 328 old_xattr = simple_xattr_set(cache, &attrs->xattrs, name, value, size, flags); 329 if (IS_ERR(old_xattr)) 330 return PTR_ERR(old_xattr); 331 332 simple_xattr_free_rcu(old_xattr); 333 return 0; 334 } 335 336 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler, 337 struct dentry *unused, struct inode *inode, 338 const char *suffix, void *value, size_t size) 339 { 340 const char *name = xattr_full_name(handler, suffix); 341 struct kernfs_node *kn = inode->i_private; 342 343 return kernfs_xattr_get(kn, name, value, size); 344 } 345 346 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler, 347 struct mnt_idmap *idmap, 348 struct dentry *unused, struct inode *inode, 349 const char *suffix, const void *value, 350 size_t size, int flags) 351 { 352 const char *name = xattr_full_name(handler, suffix); 353 struct kernfs_node *kn = inode->i_private; 354 355 return kernfs_xattr_set(kn, name, value, size, flags); 356 } 357 358 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler, 359 struct mnt_idmap *idmap, 360 struct dentry *unused, struct inode *inode, 361 const char *suffix, const void *value, 362 size_t size, int flags) 363 { 364 const char *full_name = xattr_full_name(handler, suffix); 365 struct kernfs_node *kn = inode->i_private; 366 struct kernfs_iattrs *attrs; 367 368 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR)) 369 return -EOPNOTSUPP; 370 371 attrs = kernfs_iattrs(kn); 372 if (!attrs) 373 return -ENOMEM; 374 375 /* See comment in kernfs_xattr_set() about locking. */ 376 CLASS(kernfs_node_lock, lock)(kn); 377 378 return simple_xattr_set_limited(&kernfs_root(kn)->xa_cache, 379 &attrs->xattrs, &attrs->xattr_limits, 380 full_name, value, size, flags); 381 } 382 383 static const struct xattr_handler kernfs_trusted_xattr_handler = { 384 .prefix = XATTR_TRUSTED_PREFIX, 385 .get = kernfs_vfs_xattr_get, 386 .set = kernfs_vfs_xattr_set, 387 }; 388 389 static const struct xattr_handler kernfs_security_xattr_handler = { 390 .prefix = XATTR_SECURITY_PREFIX, 391 .get = kernfs_vfs_xattr_get, 392 .set = kernfs_vfs_xattr_set, 393 }; 394 395 static const struct xattr_handler kernfs_user_xattr_handler = { 396 .prefix = XATTR_USER_PREFIX, 397 .get = kernfs_vfs_xattr_get, 398 .set = kernfs_vfs_user_xattr_set, 399 }; 400 401 const struct xattr_handler * const kernfs_xattr_handlers[] = { 402 &kernfs_trusted_xattr_handler, 403 &kernfs_security_xattr_handler, 404 &kernfs_user_xattr_handler, 405 NULL 406 }; 407