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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 | /* File: fs/xattr.c Extended attribute handling. Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org> Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com> Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com> */ #include <linux/fs.h> #include <linux/slab.h> #include <linux/smp_lock.h> #include <linux/file.h> #include <linux/xattr.h> #include <linux/namei.h> #include <linux/security.h> #include <linux/syscalls.h> #include <linux/module.h> #include <linux/fsnotify.h> #include <asm/uaccess.h> /* * Check permissions for extended attribute access. This is a bit complicated * because different namespaces have very different rules. */ static int xattr_permission(struct inode *inode, const char *name, int mask) { /* * We can never set or remove an extended attribute on a read-only * filesystem or on an immutable / append-only inode. */ if (mask & MAY_WRITE) { if (IS_RDONLY(inode)) return -EROFS; if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) return -EPERM; } /* * No restriction for security.* and system.* from the VFS. Decision * on these is left to the underlying filesystem / security module. */ if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) || !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) return 0; /* * The trusted.* namespace can only accessed by a privilegued user. */ if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM); if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) { if (!S_ISREG(inode->i_mode) && (!S_ISDIR(inode->i_mode) || inode->i_mode & S_ISVTX)) return -EPERM; } return permission(inode, mask, NULL); } int vfs_setxattr(struct dentry *dentry, char *name, void *value, size_t size, int flags) { struct inode *inode = dentry->d_inode; int error; error = xattr_permission(inode, name, MAY_WRITE); if (error) return error; mutex_lock(&inode->i_mutex); error = security_inode_setxattr(dentry, name, value, size, flags); if (error) goto out; error = -EOPNOTSUPP; if (inode->i_op->setxattr) { error = inode->i_op->setxattr(dentry, name, value, size, flags); if (!error) { fsnotify_xattr(dentry); security_inode_post_setxattr(dentry, name, value, size, flags); } } else if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) { const char *suffix = name + XATTR_SECURITY_PREFIX_LEN; error = security_inode_setsecurity(inode, suffix, value, size, flags); if (!error) fsnotify_xattr(dentry); } out: mutex_unlock(&inode->i_mutex); return error; } EXPORT_SYMBOL_GPL(vfs_setxattr); ssize_t vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size) { struct inode *inode = dentry->d_inode; int error; error = xattr_permission(inode, name, MAY_READ); if (error) return error; error = security_inode_getxattr(dentry, name); if (error) return error; if (inode->i_op->getxattr) error = inode->i_op->getxattr(dentry, name, value, size); else error = -EOPNOTSUPP; if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) { const char *suffix = name + XATTR_SECURITY_PREFIX_LEN; int ret = security_inode_getsecurity(inode, suffix, value, size, error); /* * Only overwrite the return value if a security module * is actually active. */ if (ret != -EOPNOTSUPP) error = ret; } return error; } EXPORT_SYMBOL_GPL(vfs_getxattr); int vfs_removexattr(struct dentry *dentry, char *name) { struct inode *inode = dentry->d_inode; int error; if (!inode->i_op->removexattr) return -EOPNOTSUPP; error = xattr_permission(inode, name, MAY_WRITE); if (error) return error; error = security_inode_removexattr(dentry, name); if (error) return error; mutex_lock(&inode->i_mutex); error = inode->i_op->removexattr(dentry, name); mutex_unlock(&inode->i_mutex); if (!error) fsnotify_xattr(dentry); return error; } EXPORT_SYMBOL_GPL(vfs_removexattr); /* * Extended attribute SET operations */ static long setxattr(struct dentry *d, char __user *name, void __user *value, size_t size, int flags) { int error; void *kvalue = NULL; char kname[XATTR_NAME_MAX + 1]; if (flags & ~(XATTR_CREATE|XATTR_REPLACE)) return -EINVAL; error = strncpy_from_user(kname, name, sizeof(kname)); if (error == 0 || error == sizeof(kname)) error = -ERANGE; if (error < 0) return error; if (size) { if (size > XATTR_SIZE_MAX) return -E2BIG; kvalue = kmalloc(size, GFP_KERNEL); if (!kvalue) return -ENOMEM; if (copy_from_user(kvalue, value, size)) { kfree(kvalue); return -EFAULT; } } error = vfs_setxattr(d, kname, kvalue, size, flags); kfree(kvalue); return error; } asmlinkage long sys_setxattr(char __user *path, char __user *name, void __user *value, size_t size, int flags) { struct nameidata nd; int error; error = user_path_walk(path, &nd); if (error) return error; error = setxattr(nd.dentry, name, value, size, flags); path_release(&nd); return error; } asmlinkage long sys_lsetxattr(char __user *path, char __user *name, void __user *value, size_t size, int flags) { struct nameidata nd; int error; error = user_path_walk_link(path, &nd); if (error) return error; error = setxattr(nd.dentry, name, value, size, flags); path_release(&nd); return error; } asmlinkage long sys_fsetxattr(int fd, char __user *name, void __user *value, size_t size, int flags) { struct file *f; int error = -EBADF; f = fget(fd); if (!f) return error; error = setxattr(f->f_dentry, name, value, size, flags); fput(f); return error; } /* * Extended attribute GET operations */ static ssize_t getxattr(struct dentry *d, char __user *name, void __user *value, size_t size) { ssize_t error; void *kvalue = NULL; char kname[XATTR_NAME_MAX + 1]; error = strncpy_from_user(kname, name, sizeof(kname)); if (error == 0 || error == sizeof(kname)) error = -ERANGE; if (error < 0) return error; if (size) { if (size > XATTR_SIZE_MAX) size = XATTR_SIZE_MAX; kvalue = kzalloc(size, GFP_KERNEL); if (!kvalue) return -ENOMEM; } error = vfs_getxattr(d, kname, kvalue, size); if (error > 0) { if (size && copy_to_user(value, kvalue, error)) error = -EFAULT; } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) { /* The file system tried to returned a value bigger than XATTR_SIZE_MAX bytes. Not possible. */ error = -E2BIG; } kfree(kvalue); return error; } asmlinkage ssize_t sys_getxattr(char __user *path, char __user *name, void __user *value, size_t size) { struct nameidata nd; ssize_t error; error = user_path_walk(path, &nd); if (error) return error; error = getxattr(nd.dentry, name, value, size); path_release(&nd); return error; } asmlinkage ssize_t sys_lgetxattr(char __user *path, char __user *name, void __user *value, size_t size) { struct nameidata nd; ssize_t error; error = user_path_walk_link(path, &nd); if (error) return error; error = getxattr(nd.dentry, name, value, size); path_release(&nd); return error; } asmlinkage ssize_t sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size) { struct file *f; ssize_t error = -EBADF; f = fget(fd); if (!f) return error; error = getxattr(f->f_dentry, name, value, size); fput(f); return error; } /* * Extended attribute LIST operations */ static ssize_t listxattr(struct dentry *d, char __user *list, size_t size) { ssize_t error; char *klist = NULL; if (size) { if (size > XATTR_LIST_MAX) size = XATTR_LIST_MAX; klist = kmalloc(size, GFP_KERNEL); if (!klist) return -ENOMEM; } error = security_inode_listxattr(d); if (error) goto out; error = -EOPNOTSUPP; if (d->d_inode->i_op && d->d_inode->i_op->listxattr) { error = d->d_inode->i_op->listxattr(d, klist, size); } else { error = security_inode_listsecurity(d->d_inode, klist, size); if (size && error > size) error = -ERANGE; } if (error > 0) { if (size && copy_to_user(list, klist, error)) error = -EFAULT; } else if (error == -ERANGE && size >= XATTR_LIST_MAX) { /* The file system tried to returned a list bigger than XATTR_LIST_MAX bytes. Not possible. */ error = -E2BIG; } out: kfree(klist); return error; } asmlinkage ssize_t sys_listxattr(char __user *path, char __user *list, size_t size) { struct nameidata nd; ssize_t error; error = user_path_walk(path, &nd); if (error) return error; error = listxattr(nd.dentry, list, size); path_release(&nd); return error; } asmlinkage ssize_t sys_llistxattr(char __user *path, char __user *list, size_t size) { struct nameidata nd; ssize_t error; error = user_path_walk_link(path, &nd); if (error) return error; error = listxattr(nd.dentry, list, size); path_release(&nd); return error; } asmlinkage ssize_t sys_flistxattr(int fd, char __user *list, size_t size) { struct file *f; ssize_t error = -EBADF; f = fget(fd); if (!f) return error; error = listxattr(f->f_dentry, list, size); fput(f); return error; } /* * Extended attribute REMOVE operations */ static long removexattr(struct dentry *d, char __user *name) { int error; char kname[XATTR_NAME_MAX + 1]; error = strncpy_from_user(kname, name, sizeof(kname)); if (error == 0 || error == sizeof(kname)) error = -ERANGE; if (error < 0) return error; return vfs_removexattr(d, kname); } asmlinkage long sys_removexattr(char __user *path, char __user *name) { struct nameidata nd; int error; error = user_path_walk(path, &nd); if (error) return error; error = removexattr(nd.dentry, name); path_release(&nd); return error; } asmlinkage long sys_lremovexattr(char __user *path, char __user *name) { struct nameidata nd; int error; error = user_path_walk_link(path, &nd); if (error) return error; error = removexattr(nd.dentry, name); path_release(&nd); return error; } asmlinkage long sys_fremovexattr(int fd, char __user *name) { struct file *f; int error = -EBADF; f = fget(fd); if (!f) return error; error = removexattr(f->f_dentry, name); fput(f); return error; } static const char * strcmp_prefix(const char *a, const char *a_prefix) { while (*a_prefix && *a == *a_prefix) { a++; a_prefix++; } return *a_prefix ? NULL : a; } /* * In order to implement different sets of xattr operations for each xattr * prefix with the generic xattr API, a filesystem should create a * null-terminated array of struct xattr_handler (one for each prefix) and * hang a pointer to it off of the s_xattr field of the superblock. * * The generic_fooxattr() functions will use this list to dispatch xattr * operations to the correct xattr_handler. */ #define for_each_xattr_handler(handlers, handler) \ for ((handler) = *(handlers)++; \ (handler) != NULL; \ (handler) = *(handlers)++) /* * Find the xattr_handler with the matching prefix. */ static struct xattr_handler * xattr_resolve_name(struct xattr_handler **handlers, const char **name) { struct xattr_handler *handler; if (!*name) return NULL; for_each_xattr_handler(handlers, handler) { const char *n = strcmp_prefix(*name, handler->prefix); if (n) { *name = n; break; } } return handler; } /* * Find the handler for the prefix and dispatch its get() operation. */ ssize_t generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size) { struct xattr_handler *handler; struct inode *inode = dentry->d_inode; handler = xattr_resolve_name(inode->i_sb->s_xattr, &name); if (!handler) return -EOPNOTSUPP; return handler->get(inode, name, buffer, size); } /* * Combine the results of the list() operation from every xattr_handler in the * list. */ ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size) { struct inode *inode = dentry->d_inode; struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr; unsigned int size = 0; if (!buffer) { for_each_xattr_handler(handlers, handler) size += handler->list(inode, NULL, 0, NULL, 0); } else { char *buf = buffer; for_each_xattr_handler(handlers, handler) { size = handler->list(inode, buf, buffer_size, NULL, 0); if (size > buffer_size) return -ERANGE; buf += size; buffer_size -= size; } size = buf - buffer; } return size; } /* * Find the handler for the prefix and dispatch its set() operation. */ int generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags) { struct xattr_handler *handler; struct inode *inode = dentry->d_inode; if (size == 0) value = ""; /* empty EA, do not remove */ handler = xattr_resolve_name(inode->i_sb->s_xattr, &name); if (!handler) return -EOPNOTSUPP; return handler->set(inode, name, value, size, flags); } /* * Find the handler for the prefix and dispatch its set() operation to remove * any associated extended attribute. */ int generic_removexattr(struct dentry *dentry, const char *name) { struct xattr_handler *handler; struct inode *inode = dentry->d_inode; handler = xattr_resolve_name(inode->i_sb->s_xattr, &name); if (!handler) return -EOPNOTSUPP; return handler->set(inode, name, NULL, 0, XATTR_REPLACE); } EXPORT_SYMBOL(generic_getxattr); EXPORT_SYMBOL(generic_listxattr); EXPORT_SYMBOL(generic_setxattr); EXPORT_SYMBOL(generic_removexattr); |