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