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 * Returns 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_rwsem); 105 ret = __kernfs_setattr(kn, iattr); 106 up_write(&root->kernfs_rwsem); 107 return ret; 108 } 109 110 int kernfs_iop_setattr(struct user_namespace *mnt_userns, 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_rwsem); 123 error = setattr_prepare(&init_user_ns, 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(&init_user_ns, inode, iattr); 133 134 out: 135 up_write(&root->kernfs_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 user_namespace *mnt_userns, 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_rwsem); 193 spin_lock(&inode->i_lock); 194 kernfs_refresh_inode(kn, inode); 195 generic_fillattr(&init_user_ns, inode, stat); 196 spin_unlock(&inode->i_lock); 197 up_read(&root->kernfs_rwsem); 198 199 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 = &ram_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 struct kernfs_root *root; 282 int ret; 283 284 if (mask & MAY_NOT_BLOCK) 285 return -ECHILD; 286 287 kn = inode->i_private; 288 root = kernfs_root(kn); 289 290 down_read(&root->kernfs_rwsem); 291 spin_lock(&inode->i_lock); 292 kernfs_refresh_inode(kn, inode); 293 ret = generic_permission(&init_user_ns, inode, mask); 294 spin_unlock(&inode->i_lock); 295 up_read(&root->kernfs_rwsem); 296 297 return ret; 298 } 299 300 int kernfs_xattr_get(struct kernfs_node *kn, const char *name, 301 void *value, size_t size) 302 { 303 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn); 304 if (!attrs) 305 return -ENODATA; 306 307 return simple_xattr_get(&attrs->xattrs, name, value, size); 308 } 309 310 int kernfs_xattr_set(struct kernfs_node *kn, const char *name, 311 const void *value, size_t size, int flags) 312 { 313 struct kernfs_iattrs *attrs = kernfs_iattrs(kn); 314 if (!attrs) 315 return -ENOMEM; 316 317 return simple_xattr_set(&attrs->xattrs, name, value, size, flags, NULL); 318 } 319 320 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler, 321 struct dentry *unused, struct inode *inode, 322 const char *suffix, void *value, size_t size) 323 { 324 const char *name = xattr_full_name(handler, suffix); 325 struct kernfs_node *kn = inode->i_private; 326 327 return kernfs_xattr_get(kn, name, value, size); 328 } 329 330 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler, 331 struct user_namespace *mnt_userns, 332 struct dentry *unused, struct inode *inode, 333 const char *suffix, const void *value, 334 size_t size, int flags) 335 { 336 const char *name = xattr_full_name(handler, suffix); 337 struct kernfs_node *kn = inode->i_private; 338 339 return kernfs_xattr_set(kn, name, value, size, flags); 340 } 341 342 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn, 343 const char *full_name, 344 struct simple_xattrs *xattrs, 345 const void *value, size_t size, int flags) 346 { 347 atomic_t *sz = &kn->iattr->user_xattr_size; 348 atomic_t *nr = &kn->iattr->nr_user_xattrs; 349 ssize_t removed_size; 350 int ret; 351 352 if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) { 353 ret = -ENOSPC; 354 goto dec_count_out; 355 } 356 357 if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) { 358 ret = -ENOSPC; 359 goto dec_size_out; 360 } 361 362 ret = simple_xattr_set(xattrs, full_name, value, size, flags, 363 &removed_size); 364 365 if (!ret && removed_size >= 0) 366 size = removed_size; 367 else if (!ret) 368 return 0; 369 dec_size_out: 370 atomic_sub(size, sz); 371 dec_count_out: 372 atomic_dec(nr); 373 return ret; 374 } 375 376 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn, 377 const char *full_name, 378 struct simple_xattrs *xattrs, 379 const void *value, size_t size, int flags) 380 { 381 atomic_t *sz = &kn->iattr->user_xattr_size; 382 atomic_t *nr = &kn->iattr->nr_user_xattrs; 383 ssize_t removed_size; 384 int ret; 385 386 ret = simple_xattr_set(xattrs, full_name, value, size, flags, 387 &removed_size); 388 389 if (removed_size >= 0) { 390 atomic_sub(removed_size, sz); 391 atomic_dec(nr); 392 } 393 394 return ret; 395 } 396 397 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler, 398 struct user_namespace *mnt_userns, 399 struct dentry *unused, struct inode *inode, 400 const char *suffix, const void *value, 401 size_t size, int flags) 402 { 403 const char *full_name = xattr_full_name(handler, suffix); 404 struct kernfs_node *kn = inode->i_private; 405 struct kernfs_iattrs *attrs; 406 407 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR)) 408 return -EOPNOTSUPP; 409 410 attrs = kernfs_iattrs(kn); 411 if (!attrs) 412 return -ENOMEM; 413 414 if (value) 415 return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs, 416 value, size, flags); 417 else 418 return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs, 419 value, size, flags); 420 421 } 422 423 static const struct xattr_handler kernfs_trusted_xattr_handler = { 424 .prefix = XATTR_TRUSTED_PREFIX, 425 .get = kernfs_vfs_xattr_get, 426 .set = kernfs_vfs_xattr_set, 427 }; 428 429 static const struct xattr_handler kernfs_security_xattr_handler = { 430 .prefix = XATTR_SECURITY_PREFIX, 431 .get = kernfs_vfs_xattr_get, 432 .set = kernfs_vfs_xattr_set, 433 }; 434 435 static const struct xattr_handler kernfs_user_xattr_handler = { 436 .prefix = XATTR_USER_PREFIX, 437 .get = kernfs_vfs_xattr_get, 438 .set = kernfs_vfs_user_xattr_set, 439 }; 440 441 const struct xattr_handler *kernfs_xattr_handlers[] = { 442 &kernfs_trusted_xattr_handler, 443 &kernfs_security_xattr_handler, 444 &kernfs_user_xattr_handler, 445 NULL 446 }; 447