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 mutex_lock(&kernfs_mutex); 104 ret = __kernfs_setattr(kn, iattr); 105 mutex_unlock(&kernfs_mutex); 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 mutex_lock(&kernfs_mutex); 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 mutex_unlock(&kernfs_mutex); 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 mutex_lock(&kernfs_mutex); 189 kernfs_refresh_inode(kn, inode); 190 mutex_unlock(&kernfs_mutex); 191 192 generic_fillattr(&init_user_ns, inode, stat); 193 return 0; 194 } 195 196 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode) 197 { 198 kernfs_get(kn); 199 inode->i_private = kn; 200 inode->i_mapping->a_ops = &ram_aops; 201 inode->i_op = &kernfs_iops; 202 inode->i_generation = kernfs_gen(kn); 203 204 set_default_inode_attr(inode, kn->mode); 205 kernfs_refresh_inode(kn, inode); 206 207 /* initialize inode according to type */ 208 switch (kernfs_type(kn)) { 209 case KERNFS_DIR: 210 inode->i_op = &kernfs_dir_iops; 211 inode->i_fop = &kernfs_dir_fops; 212 if (kn->flags & KERNFS_EMPTY_DIR) 213 make_empty_dir_inode(inode); 214 break; 215 case KERNFS_FILE: 216 inode->i_size = kn->attr.size; 217 inode->i_fop = &kernfs_file_fops; 218 break; 219 case KERNFS_LINK: 220 inode->i_op = &kernfs_symlink_iops; 221 break; 222 default: 223 BUG(); 224 } 225 226 unlock_new_inode(inode); 227 } 228 229 /** 230 * kernfs_get_inode - get inode for kernfs_node 231 * @sb: super block 232 * @kn: kernfs_node to allocate inode for 233 * 234 * Get inode for @kn. If such inode doesn't exist, a new inode is 235 * allocated and basics are initialized. New inode is returned 236 * locked. 237 * 238 * LOCKING: 239 * Kernel thread context (may sleep). 240 * 241 * RETURNS: 242 * Pointer to allocated inode on success, NULL on failure. 243 */ 244 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn) 245 { 246 struct inode *inode; 247 248 inode = iget_locked(sb, kernfs_ino(kn)); 249 if (inode && (inode->i_state & I_NEW)) 250 kernfs_init_inode(kn, inode); 251 252 return inode; 253 } 254 255 /* 256 * The kernfs_node serves as both an inode and a directory entry for 257 * kernfs. To prevent the kernfs inode numbers from being freed 258 * prematurely we take a reference to kernfs_node from the kernfs inode. A 259 * super_operations.evict_inode() implementation is needed to drop that 260 * reference upon inode destruction. 261 */ 262 void kernfs_evict_inode(struct inode *inode) 263 { 264 struct kernfs_node *kn = inode->i_private; 265 266 truncate_inode_pages_final(&inode->i_data); 267 clear_inode(inode); 268 kernfs_put(kn); 269 } 270 271 int kernfs_iop_permission(struct user_namespace *mnt_userns, 272 struct inode *inode, int mask) 273 { 274 struct kernfs_node *kn; 275 276 if (mask & MAY_NOT_BLOCK) 277 return -ECHILD; 278 279 kn = inode->i_private; 280 281 mutex_lock(&kernfs_mutex); 282 kernfs_refresh_inode(kn, inode); 283 mutex_unlock(&kernfs_mutex); 284 285 return generic_permission(&init_user_ns, inode, mask); 286 } 287 288 int kernfs_xattr_get(struct kernfs_node *kn, const char *name, 289 void *value, size_t size) 290 { 291 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn); 292 if (!attrs) 293 return -ENODATA; 294 295 return simple_xattr_get(&attrs->xattrs, name, value, size); 296 } 297 298 int kernfs_xattr_set(struct kernfs_node *kn, const char *name, 299 const void *value, size_t size, int flags) 300 { 301 struct kernfs_iattrs *attrs = kernfs_iattrs(kn); 302 if (!attrs) 303 return -ENOMEM; 304 305 return simple_xattr_set(&attrs->xattrs, name, value, size, flags, NULL); 306 } 307 308 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler, 309 struct dentry *unused, struct inode *inode, 310 const char *suffix, void *value, size_t size) 311 { 312 const char *name = xattr_full_name(handler, suffix); 313 struct kernfs_node *kn = inode->i_private; 314 315 return kernfs_xattr_get(kn, name, value, size); 316 } 317 318 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler, 319 struct user_namespace *mnt_userns, 320 struct dentry *unused, struct inode *inode, 321 const char *suffix, const void *value, 322 size_t size, int flags) 323 { 324 const char *name = xattr_full_name(handler, suffix); 325 struct kernfs_node *kn = inode->i_private; 326 327 return kernfs_xattr_set(kn, name, value, size, flags); 328 } 329 330 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn, 331 const char *full_name, 332 struct simple_xattrs *xattrs, 333 const void *value, size_t size, int flags) 334 { 335 atomic_t *sz = &kn->iattr->user_xattr_size; 336 atomic_t *nr = &kn->iattr->nr_user_xattrs; 337 ssize_t removed_size; 338 int ret; 339 340 if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) { 341 ret = -ENOSPC; 342 goto dec_count_out; 343 } 344 345 if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) { 346 ret = -ENOSPC; 347 goto dec_size_out; 348 } 349 350 ret = simple_xattr_set(xattrs, full_name, value, size, flags, 351 &removed_size); 352 353 if (!ret && removed_size >= 0) 354 size = removed_size; 355 else if (!ret) 356 return 0; 357 dec_size_out: 358 atomic_sub(size, sz); 359 dec_count_out: 360 atomic_dec(nr); 361 return ret; 362 } 363 364 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn, 365 const char *full_name, 366 struct simple_xattrs *xattrs, 367 const void *value, size_t size, int flags) 368 { 369 atomic_t *sz = &kn->iattr->user_xattr_size; 370 atomic_t *nr = &kn->iattr->nr_user_xattrs; 371 ssize_t removed_size; 372 int ret; 373 374 ret = simple_xattr_set(xattrs, full_name, value, size, flags, 375 &removed_size); 376 377 if (removed_size >= 0) { 378 atomic_sub(removed_size, sz); 379 atomic_dec(nr); 380 } 381 382 return ret; 383 } 384 385 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler, 386 struct user_namespace *mnt_userns, 387 struct dentry *unused, struct inode *inode, 388 const char *suffix, const void *value, 389 size_t size, int flags) 390 { 391 const char *full_name = xattr_full_name(handler, suffix); 392 struct kernfs_node *kn = inode->i_private; 393 struct kernfs_iattrs *attrs; 394 395 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR)) 396 return -EOPNOTSUPP; 397 398 attrs = kernfs_iattrs(kn); 399 if (!attrs) 400 return -ENOMEM; 401 402 if (value) 403 return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs, 404 value, size, flags); 405 else 406 return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs, 407 value, size, flags); 408 409 } 410 411 static const struct xattr_handler kernfs_trusted_xattr_handler = { 412 .prefix = XATTR_TRUSTED_PREFIX, 413 .get = kernfs_vfs_xattr_get, 414 .set = kernfs_vfs_xattr_set, 415 }; 416 417 static const struct xattr_handler kernfs_security_xattr_handler = { 418 .prefix = XATTR_SECURITY_PREFIX, 419 .get = kernfs_vfs_xattr_get, 420 .set = kernfs_vfs_xattr_set, 421 }; 422 423 static const struct xattr_handler kernfs_user_xattr_handler = { 424 .prefix = XATTR_USER_PREFIX, 425 .get = kernfs_vfs_xattr_get, 426 .set = kernfs_vfs_user_xattr_set, 427 }; 428 429 const struct xattr_handler *kernfs_xattr_handlers[] = { 430 &kernfs_trusted_xattr_handler, 431 &kernfs_security_xattr_handler, 432 &kernfs_user_xattr_handler, 433 NULL 434 }; 435