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_noalloc(kn); 145 146 return simple_xattr_list(d_inode(dentry), attrs ? &attrs->xattrs : NULL, buf, size); 147 } 148 149 static inline void set_default_inode_attr(struct inode *inode, umode_t mode) 150 { 151 inode->i_mode = mode; 152 simple_inode_init_ts(inode); 153 } 154 155 static inline void set_inode_attr(struct inode *inode, 156 struct kernfs_iattrs *attrs) 157 { 158 inode->i_uid = attrs->ia_uid; 159 inode->i_gid = attrs->ia_gid; 160 inode_set_atime_to_ts(inode, attrs->ia_atime); 161 inode_set_mtime_to_ts(inode, attrs->ia_mtime); 162 inode_set_ctime_to_ts(inode, attrs->ia_ctime); 163 } 164 165 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode) 166 { 167 struct kernfs_iattrs *attrs; 168 169 inode->i_mode = kn->mode; 170 attrs = kernfs_iattrs_noalloc(kn); 171 if (attrs) 172 /* 173 * kernfs_node has non-default attributes get them from 174 * persistent copy in kernfs_node. 175 */ 176 set_inode_attr(inode, attrs); 177 178 if (kernfs_type(kn) == KERNFS_DIR && !(kn->flags & KERNFS_REMOVING)) 179 set_nlink(inode, kn->dir.subdirs + 2); 180 } 181 182 int kernfs_iop_getattr(struct mnt_idmap *idmap, 183 const struct path *path, struct kstat *stat, 184 u32 request_mask, unsigned int query_flags) 185 { 186 struct inode *inode = d_inode(path->dentry); 187 struct kernfs_node *kn = inode->i_private; 188 struct kernfs_root *root = kernfs_root(kn); 189 190 down_read(&root->kernfs_iattr_rwsem); 191 kernfs_refresh_inode(kn, inode); 192 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); 193 up_read(&root->kernfs_iattr_rwsem); 194 195 return 0; 196 } 197 198 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) 199 { 200 kernfs_get(kn); 201 inode->i_private = kn; 202 inode->i_mapping->a_ops = &ram_aops; 203 inode->i_op = &kernfs_iops; 204 inode->i_generation = kernfs_gen(kn); 205 206 set_default_inode_attr(inode, kn->mode); 207 kernfs_refresh_inode(kn, inode); 208 209 /* initialize inode according to type */ 210 switch (kernfs_type(kn)) { 211 case KERNFS_DIR: 212 inode->i_op = &kernfs_dir_iops; 213 inode->i_fop = &kernfs_dir_fops; 214 if (kn->flags & KERNFS_EMPTY_DIR) 215 make_empty_dir_inode(inode); 216 break; 217 case KERNFS_FILE: 218 inode->i_size = kn->attr.size; 219 inode->i_fop = &kernfs_file_fops; 220 break; 221 case KERNFS_LINK: 222 inode->i_op = &kernfs_symlink_iops; 223 break; 224 default: 225 BUG(); 226 } 227 228 unlock_new_inode(inode); 229 } 230 231 /** 232 * kernfs_get_inode - get inode for kernfs_node 233 * @sb: super block 234 * @kn: kernfs_node to allocate inode for 235 * 236 * Get inode for @kn. If such inode doesn't exist, a new inode is 237 * allocated and basics are initialized. New inode is returned 238 * locked. 239 * 240 * Locking: 241 * Kernel thread context (may sleep). 242 * 243 * Return: 244 * Pointer to allocated inode on success, %NULL on failure. 245 */ 246 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn) 247 { 248 struct inode *inode; 249 250 inode = iget_locked(sb, kernfs_ino(kn)); 251 if (inode && (inode_state_read_once(inode) & I_NEW)) 252 kernfs_init_inode(kn, inode); 253 254 return inode; 255 } 256 257 /* 258 * The kernfs_node serves as both an inode and a directory entry for 259 * kernfs. To prevent the kernfs inode numbers from being freed 260 * prematurely we take a reference to kernfs_node from the kernfs inode. A 261 * super_operations.evict_inode() implementation is needed to drop that 262 * reference upon inode destruction. 263 */ 264 void kernfs_evict_inode(struct inode *inode) 265 { 266 struct kernfs_node *kn = inode->i_private; 267 268 truncate_inode_pages_final(&inode->i_data); 269 clear_inode(inode); 270 kernfs_put(kn); 271 } 272 273 int kernfs_iop_permission(struct mnt_idmap *idmap, 274 struct inode *inode, int mask) 275 { 276 struct kernfs_node *kn; 277 struct kernfs_root *root; 278 int ret; 279 280 if (mask & MAY_NOT_BLOCK) 281 return -ECHILD; 282 283 kn = inode->i_private; 284 root = kernfs_root(kn); 285 286 down_read(&root->kernfs_iattr_rwsem); 287 kernfs_refresh_inode(kn, inode); 288 ret = generic_permission(&nop_mnt_idmap, inode, mask); 289 up_read(&root->kernfs_iattr_rwsem); 290 291 return ret; 292 } 293 294 int kernfs_xattr_get(struct kernfs_node *kn, const char *name, 295 void *value, size_t size) 296 { 297 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn); 298 struct simple_xattr_cache *cache = &kernfs_root(kn)->xa_cache; 299 300 if (!attrs) 301 return -ENODATA; 302 303 return simple_xattr_get(cache, &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 simple_xattr *old_xattr; 310 struct kernfs_iattrs *attrs; 311 struct simple_xattr_cache *cache = &kernfs_root(kn)->xa_cache; 312 313 attrs = kernfs_iattrs(kn); 314 if (!attrs) 315 return -ENOMEM; 316 317 /* 318 * Protect xattr modifications with the hashed per-node mutex. 319 * Multiple superblocks (with different namespaces) can share the same 320 * kernfs_node, so inode locking alone is insufficient. The hashed mutex 321 * ensures serialization of concurrent xattr operations on the same node, 322 * including the lazy allocation of the xattrs structure itself. 323 */ 324 CLASS(kernfs_node_lock, lock)(kn); 325 326 old_xattr = simple_xattr_set(cache, &attrs->xattrs, name, value, size, flags); 327 if (IS_ERR(old_xattr)) 328 return PTR_ERR(old_xattr); 329 330 simple_xattr_free_rcu(old_xattr); 331 return 0; 332 } 333 334 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler, 335 struct dentry *unused, struct inode *inode, 336 const char *suffix, void *value, size_t size) 337 { 338 const char *name = xattr_full_name(handler, suffix); 339 struct kernfs_node *kn = inode->i_private; 340 341 return kernfs_xattr_get(kn, name, value, size); 342 } 343 344 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler, 345 struct mnt_idmap *idmap, 346 struct dentry *unused, struct inode *inode, 347 const char *suffix, const void *value, 348 size_t size, int flags) 349 { 350 const char *name = xattr_full_name(handler, suffix); 351 struct kernfs_node *kn = inode->i_private; 352 353 return kernfs_xattr_set(kn, name, value, size, flags); 354 } 355 356 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler, 357 struct mnt_idmap *idmap, 358 struct dentry *unused, struct inode *inode, 359 const char *suffix, const void *value, 360 size_t size, int flags) 361 { 362 const char *full_name = xattr_full_name(handler, suffix); 363 struct kernfs_node *kn = inode->i_private; 364 struct kernfs_iattrs *attrs; 365 366 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR)) 367 return -EOPNOTSUPP; 368 369 attrs = kernfs_iattrs(kn); 370 if (!attrs) 371 return -ENOMEM; 372 373 /* See comment in kernfs_xattr_set() about locking. */ 374 CLASS(kernfs_node_lock, lock)(kn); 375 376 return simple_xattr_set_limited(&kernfs_root(kn)->xa_cache, 377 &attrs->xattrs, &attrs->xattr_limits, 378 full_name, value, size, flags); 379 } 380 381 static const struct xattr_handler kernfs_trusted_xattr_handler = { 382 .prefix = XATTR_TRUSTED_PREFIX, 383 .get = kernfs_vfs_xattr_get, 384 .set = kernfs_vfs_xattr_set, 385 }; 386 387 static const struct xattr_handler kernfs_security_xattr_handler = { 388 .prefix = XATTR_SECURITY_PREFIX, 389 .get = kernfs_vfs_xattr_get, 390 .set = kernfs_vfs_xattr_set, 391 }; 392 393 static const struct xattr_handler kernfs_user_xattr_handler = { 394 .prefix = XATTR_USER_PREFIX, 395 .get = kernfs_vfs_xattr_get, 396 .set = kernfs_vfs_user_xattr_set, 397 }; 398 399 const struct xattr_handler * const kernfs_xattr_handlers[] = { 400 &kernfs_trusted_xattr_handler, 401 &kernfs_security_xattr_handler, 402 &kernfs_user_xattr_handler, 403 NULL 404 }; 405