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; 102 103 down_write(&kernfs_rwsem); 104 ret = __kernfs_setattr(kn, iattr); 105 up_write(&kernfs_rwsem); 106 return ret; 107 } 108 109 int kernfs_iop_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, 110 struct iattr *iattr) 111 { 112 struct inode *inode = d_inode(dentry); 113 struct kernfs_node *kn = inode->i_private; 114 int error; 115 116 if (!kn) 117 return -EINVAL; 118 119 down_write(&kernfs_rwsem); 120 error = setattr_prepare(&init_user_ns, dentry, iattr); 121 if (error) 122 goto out; 123 124 error = __kernfs_setattr(kn, iattr); 125 if (error) 126 goto out; 127 128 /* this ignores size changes */ 129 setattr_copy(&init_user_ns, inode, iattr); 130 131 out: 132 up_write(&kernfs_rwsem); 133 return error; 134 } 135 136 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size) 137 { 138 struct kernfs_node *kn = kernfs_dentry_node(dentry); 139 struct kernfs_iattrs *attrs; 140 141 attrs = kernfs_iattrs(kn); 142 if (!attrs) 143 return -ENOMEM; 144 145 return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size); 146 } 147 148 static inline void set_default_inode_attr(struct inode *inode, umode_t mode) 149 { 150 inode->i_mode = mode; 151 inode->i_atime = inode->i_mtime = 152 inode->i_ctime = current_time(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->i_atime = attrs->ia_atime; 161 inode->i_mtime = attrs->ia_mtime; 162 inode->i_ctime = attrs->ia_ctime; 163 } 164 165 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode) 166 { 167 struct kernfs_iattrs *attrs = kn->iattr; 168 169 inode->i_mode = kn->mode; 170 if (attrs) 171 /* 172 * kernfs_node has non-default attributes get them from 173 * persistent copy in kernfs_node. 174 */ 175 set_inode_attr(inode, attrs); 176 177 if (kernfs_type(kn) == KERNFS_DIR) 178 set_nlink(inode, kn->dir.subdirs + 2); 179 } 180 181 int kernfs_iop_getattr(struct user_namespace *mnt_userns, 182 const struct path *path, struct kstat *stat, 183 u32 request_mask, unsigned int query_flags) 184 { 185 struct inode *inode = d_inode(path->dentry); 186 struct kernfs_node *kn = inode->i_private; 187 188 down_read(&kernfs_rwsem); 189 spin_lock(&inode->i_lock); 190 kernfs_refresh_inode(kn, inode); 191 generic_fillattr(&init_user_ns, inode, stat); 192 spin_unlock(&inode->i_lock); 193 up_read(&kernfs_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 * RETURNS: 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->i_state & 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 user_namespace *mnt_userns, 274 struct inode *inode, int mask) 275 { 276 struct kernfs_node *kn; 277 int ret; 278 279 if (mask & MAY_NOT_BLOCK) 280 return -ECHILD; 281 282 kn = inode->i_private; 283 284 down_read(&kernfs_rwsem); 285 spin_lock(&inode->i_lock); 286 kernfs_refresh_inode(kn, inode); 287 ret = generic_permission(&init_user_ns, inode, mask); 288 spin_unlock(&inode->i_lock); 289 up_read(&kernfs_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 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