| 1 | /* |
| 2 | File: fs/xattr.c |
| 3 | |
| 4 | Extended attribute handling. |
| 5 | |
| 6 | Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org> |
| 7 | Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com> |
| 8 | Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com> |
| 9 | */ |
| 10 | #include <linux/fs.h> |
| 11 | #include <linux/slab.h> |
| 12 | #include <linux/file.h> |
| 13 | #include <linux/xattr.h> |
| 14 | #include <linux/mount.h> |
| 15 | #include <linux/namei.h> |
| 16 | #include <linux/security.h> |
| 17 | #include <linux/evm.h> |
| 18 | #include <linux/syscalls.h> |
| 19 | #include <linux/module.h> |
| 20 | #include <linux/fsnotify.h> |
| 21 | #include <linux/audit.h> |
| 22 | #include <asm/uaccess.h> |
| 23 | |
| 24 | |
| 25 | /* |
| 26 | * Check permissions for extended attribute access. This is a bit complicated |
| 27 | * because different namespaces have very different rules. |
| 28 | */ |
| 29 | static int |
| 30 | xattr_permission(struct inode *inode, const char *name, int mask) |
| 31 | { |
| 32 | /* |
| 33 | * We can never set or remove an extended attribute on a read-only |
| 34 | * filesystem or on an immutable / append-only inode. |
| 35 | */ |
| 36 | if (mask & MAY_WRITE) { |
| 37 | if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) |
| 38 | return -EPERM; |
| 39 | } |
| 40 | |
| 41 | /* |
| 42 | * No restriction for security.* and system.* from the VFS. Decision |
| 43 | * on these is left to the underlying filesystem / security module. |
| 44 | */ |
| 45 | if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) || |
| 46 | !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) |
| 47 | return 0; |
| 48 | |
| 49 | /* |
| 50 | * The trusted.* namespace can only be accessed by privileged users. |
| 51 | */ |
| 52 | if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) { |
| 53 | if (!capable(CAP_SYS_ADMIN)) |
| 54 | return (mask & MAY_WRITE) ? -EPERM : -ENODATA; |
| 55 | return 0; |
| 56 | } |
| 57 | |
| 58 | /* |
| 59 | * In the user.* namespace, only regular files and directories can have |
| 60 | * extended attributes. For sticky directories, only the owner and |
| 61 | * privileged users can write attributes. |
| 62 | */ |
| 63 | if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) { |
| 64 | if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode)) |
| 65 | return (mask & MAY_WRITE) ? -EPERM : -ENODATA; |
| 66 | if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) && |
| 67 | (mask & MAY_WRITE) && !inode_owner_or_capable(inode)) |
| 68 | return -EPERM; |
| 69 | } |
| 70 | |
| 71 | return inode_permission(inode, mask); |
| 72 | } |
| 73 | |
| 74 | /** |
| 75 | * __vfs_setxattr_noperm - perform setxattr operation without performing |
| 76 | * permission checks. |
| 77 | * |
| 78 | * @dentry - object to perform setxattr on |
| 79 | * @name - xattr name to set |
| 80 | * @value - value to set @name to |
| 81 | * @size - size of @value |
| 82 | * @flags - flags to pass into filesystem operations |
| 83 | * |
| 84 | * returns the result of the internal setxattr or setsecurity operations. |
| 85 | * |
| 86 | * This function requires the caller to lock the inode's i_mutex before it |
| 87 | * is executed. It also assumes that the caller will make the appropriate |
| 88 | * permission checks. |
| 89 | */ |
| 90 | int __vfs_setxattr_noperm(struct dentry *dentry, const char *name, |
| 91 | const void *value, size_t size, int flags) |
| 92 | { |
| 93 | struct inode *inode = dentry->d_inode; |
| 94 | int error = -EOPNOTSUPP; |
| 95 | int issec = !strncmp(name, XATTR_SECURITY_PREFIX, |
| 96 | XATTR_SECURITY_PREFIX_LEN); |
| 97 | |
| 98 | if (issec) |
| 99 | inode->i_flags &= ~S_NOSEC; |
| 100 | if (inode->i_op->setxattr) { |
| 101 | error = inode->i_op->setxattr(dentry, name, value, size, flags); |
| 102 | if (!error) { |
| 103 | fsnotify_xattr(dentry); |
| 104 | security_inode_post_setxattr(dentry, name, value, |
| 105 | size, flags); |
| 106 | } |
| 107 | } else if (issec) { |
| 108 | const char *suffix = name + XATTR_SECURITY_PREFIX_LEN; |
| 109 | error = security_inode_setsecurity(inode, suffix, value, |
| 110 | size, flags); |
| 111 | if (!error) |
| 112 | fsnotify_xattr(dentry); |
| 113 | } |
| 114 | |
| 115 | return error; |
| 116 | } |
| 117 | |
| 118 | |
| 119 | int |
| 120 | vfs_setxattr(struct dentry *dentry, const char *name, const void *value, |
| 121 | size_t size, int flags) |
| 122 | { |
| 123 | struct inode *inode = dentry->d_inode; |
| 124 | int error; |
| 125 | |
| 126 | error = xattr_permission(inode, name, MAY_WRITE); |
| 127 | if (error) |
| 128 | return error; |
| 129 | |
| 130 | mutex_lock(&inode->i_mutex); |
| 131 | error = security_inode_setxattr(dentry, name, value, size, flags); |
| 132 | if (error) |
| 133 | goto out; |
| 134 | |
| 135 | error = __vfs_setxattr_noperm(dentry, name, value, size, flags); |
| 136 | |
| 137 | out: |
| 138 | mutex_unlock(&inode->i_mutex); |
| 139 | return error; |
| 140 | } |
| 141 | EXPORT_SYMBOL_GPL(vfs_setxattr); |
| 142 | |
| 143 | ssize_t |
| 144 | xattr_getsecurity(struct inode *inode, const char *name, void *value, |
| 145 | size_t size) |
| 146 | { |
| 147 | void *buffer = NULL; |
| 148 | ssize_t len; |
| 149 | |
| 150 | if (!value || !size) { |
| 151 | len = security_inode_getsecurity(inode, name, &buffer, false); |
| 152 | goto out_noalloc; |
| 153 | } |
| 154 | |
| 155 | len = security_inode_getsecurity(inode, name, &buffer, true); |
| 156 | if (len < 0) |
| 157 | return len; |
| 158 | if (size < len) { |
| 159 | len = -ERANGE; |
| 160 | goto out; |
| 161 | } |
| 162 | memcpy(value, buffer, len); |
| 163 | out: |
| 164 | security_release_secctx(buffer, len); |
| 165 | out_noalloc: |
| 166 | return len; |
| 167 | } |
| 168 | EXPORT_SYMBOL_GPL(xattr_getsecurity); |
| 169 | |
| 170 | /* |
| 171 | * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr |
| 172 | * |
| 173 | * Allocate memory, if not already allocated, or re-allocate correct size, |
| 174 | * before retrieving the extended attribute. |
| 175 | * |
| 176 | * Returns the result of alloc, if failed, or the getxattr operation. |
| 177 | */ |
| 178 | ssize_t |
| 179 | vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value, |
| 180 | size_t xattr_size, gfp_t flags) |
| 181 | { |
| 182 | struct inode *inode = dentry->d_inode; |
| 183 | char *value = *xattr_value; |
| 184 | int error; |
| 185 | |
| 186 | error = xattr_permission(inode, name, MAY_READ); |
| 187 | if (error) |
| 188 | return error; |
| 189 | |
| 190 | if (!inode->i_op->getxattr) |
| 191 | return -EOPNOTSUPP; |
| 192 | |
| 193 | error = inode->i_op->getxattr(dentry, name, NULL, 0); |
| 194 | if (error < 0) |
| 195 | return error; |
| 196 | |
| 197 | if (!value || (error > xattr_size)) { |
| 198 | value = krealloc(*xattr_value, error + 1, flags); |
| 199 | if (!value) |
| 200 | return -ENOMEM; |
| 201 | memset(value, 0, error + 1); |
| 202 | } |
| 203 | |
| 204 | error = inode->i_op->getxattr(dentry, name, value, error); |
| 205 | *xattr_value = value; |
| 206 | return error; |
| 207 | } |
| 208 | |
| 209 | /* Compare an extended attribute value with the given value */ |
| 210 | int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name, |
| 211 | const char *value, size_t size, gfp_t flags) |
| 212 | { |
| 213 | char *xattr_value = NULL; |
| 214 | int rc; |
| 215 | |
| 216 | rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags); |
| 217 | if (rc < 0) |
| 218 | return rc; |
| 219 | |
| 220 | if ((rc != size) || (memcmp(xattr_value, value, rc) != 0)) |
| 221 | rc = -EINVAL; |
| 222 | else |
| 223 | rc = 0; |
| 224 | kfree(xattr_value); |
| 225 | return rc; |
| 226 | } |
| 227 | |
| 228 | ssize_t |
| 229 | vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size) |
| 230 | { |
| 231 | struct inode *inode = dentry->d_inode; |
| 232 | int error; |
| 233 | |
| 234 | error = xattr_permission(inode, name, MAY_READ); |
| 235 | if (error) |
| 236 | return error; |
| 237 | |
| 238 | error = security_inode_getxattr(dentry, name); |
| 239 | if (error) |
| 240 | return error; |
| 241 | |
| 242 | if (!strncmp(name, XATTR_SECURITY_PREFIX, |
| 243 | XATTR_SECURITY_PREFIX_LEN)) { |
| 244 | const char *suffix = name + XATTR_SECURITY_PREFIX_LEN; |
| 245 | int ret = xattr_getsecurity(inode, suffix, value, size); |
| 246 | /* |
| 247 | * Only overwrite the return value if a security module |
| 248 | * is actually active. |
| 249 | */ |
| 250 | if (ret == -EOPNOTSUPP) |
| 251 | goto nolsm; |
| 252 | return ret; |
| 253 | } |
| 254 | nolsm: |
| 255 | if (inode->i_op->getxattr) |
| 256 | error = inode->i_op->getxattr(dentry, name, value, size); |
| 257 | else |
| 258 | error = -EOPNOTSUPP; |
| 259 | |
| 260 | return error; |
| 261 | } |
| 262 | EXPORT_SYMBOL_GPL(vfs_getxattr); |
| 263 | |
| 264 | ssize_t |
| 265 | vfs_listxattr(struct dentry *d, char *list, size_t size) |
| 266 | { |
| 267 | ssize_t error; |
| 268 | |
| 269 | error = security_inode_listxattr(d); |
| 270 | if (error) |
| 271 | return error; |
| 272 | error = -EOPNOTSUPP; |
| 273 | if (d->d_inode->i_op->listxattr) { |
| 274 | error = d->d_inode->i_op->listxattr(d, list, size); |
| 275 | } else { |
| 276 | error = security_inode_listsecurity(d->d_inode, list, size); |
| 277 | if (size && error > size) |
| 278 | error = -ERANGE; |
| 279 | } |
| 280 | return error; |
| 281 | } |
| 282 | EXPORT_SYMBOL_GPL(vfs_listxattr); |
| 283 | |
| 284 | int |
| 285 | vfs_removexattr(struct dentry *dentry, const char *name) |
| 286 | { |
| 287 | struct inode *inode = dentry->d_inode; |
| 288 | int error; |
| 289 | |
| 290 | if (!inode->i_op->removexattr) |
| 291 | return -EOPNOTSUPP; |
| 292 | |
| 293 | error = xattr_permission(inode, name, MAY_WRITE); |
| 294 | if (error) |
| 295 | return error; |
| 296 | |
| 297 | error = security_inode_removexattr(dentry, name); |
| 298 | if (error) |
| 299 | return error; |
| 300 | |
| 301 | mutex_lock(&inode->i_mutex); |
| 302 | error = inode->i_op->removexattr(dentry, name); |
| 303 | mutex_unlock(&inode->i_mutex); |
| 304 | |
| 305 | if (!error) { |
| 306 | fsnotify_xattr(dentry); |
| 307 | evm_inode_post_removexattr(dentry, name); |
| 308 | } |
| 309 | return error; |
| 310 | } |
| 311 | EXPORT_SYMBOL_GPL(vfs_removexattr); |
| 312 | |
| 313 | |
| 314 | /* |
| 315 | * Extended attribute SET operations |
| 316 | */ |
| 317 | static long |
| 318 | setxattr(struct dentry *d, const char __user *name, const void __user *value, |
| 319 | size_t size, int flags) |
| 320 | { |
| 321 | int error; |
| 322 | void *kvalue = NULL; |
| 323 | char kname[XATTR_NAME_MAX + 1]; |
| 324 | |
| 325 | if (flags & ~(XATTR_CREATE|XATTR_REPLACE)) |
| 326 | return -EINVAL; |
| 327 | |
| 328 | error = strncpy_from_user(kname, name, sizeof(kname)); |
| 329 | if (error == 0 || error == sizeof(kname)) |
| 330 | error = -ERANGE; |
| 331 | if (error < 0) |
| 332 | return error; |
| 333 | |
| 334 | if (size) { |
| 335 | if (size > XATTR_SIZE_MAX) |
| 336 | return -E2BIG; |
| 337 | kvalue = memdup_user(value, size); |
| 338 | if (IS_ERR(kvalue)) |
| 339 | return PTR_ERR(kvalue); |
| 340 | } |
| 341 | |
| 342 | error = vfs_setxattr(d, kname, kvalue, size, flags); |
| 343 | kfree(kvalue); |
| 344 | return error; |
| 345 | } |
| 346 | |
| 347 | SYSCALL_DEFINE5(setxattr, const char __user *, pathname, |
| 348 | const char __user *, name, const void __user *, value, |
| 349 | size_t, size, int, flags) |
| 350 | { |
| 351 | struct path path; |
| 352 | int error; |
| 353 | |
| 354 | error = user_path(pathname, &path); |
| 355 | if (error) |
| 356 | return error; |
| 357 | error = mnt_want_write(path.mnt); |
| 358 | if (!error) { |
| 359 | error = setxattr(path.dentry, name, value, size, flags); |
| 360 | mnt_drop_write(path.mnt); |
| 361 | } |
| 362 | path_put(&path); |
| 363 | return error; |
| 364 | } |
| 365 | |
| 366 | SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname, |
| 367 | const char __user *, name, const void __user *, value, |
| 368 | size_t, size, int, flags) |
| 369 | { |
| 370 | struct path path; |
| 371 | int error; |
| 372 | |
| 373 | error = user_lpath(pathname, &path); |
| 374 | if (error) |
| 375 | return error; |
| 376 | error = mnt_want_write(path.mnt); |
| 377 | if (!error) { |
| 378 | error = setxattr(path.dentry, name, value, size, flags); |
| 379 | mnt_drop_write(path.mnt); |
| 380 | } |
| 381 | path_put(&path); |
| 382 | return error; |
| 383 | } |
| 384 | |
| 385 | SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name, |
| 386 | const void __user *,value, size_t, size, int, flags) |
| 387 | { |
| 388 | struct file *f; |
| 389 | struct dentry *dentry; |
| 390 | int error = -EBADF; |
| 391 | |
| 392 | f = fget(fd); |
| 393 | if (!f) |
| 394 | return error; |
| 395 | dentry = f->f_path.dentry; |
| 396 | audit_inode(NULL, dentry); |
| 397 | error = mnt_want_write_file(f); |
| 398 | if (!error) { |
| 399 | error = setxattr(dentry, name, value, size, flags); |
| 400 | mnt_drop_write(f->f_path.mnt); |
| 401 | } |
| 402 | fput(f); |
| 403 | return error; |
| 404 | } |
| 405 | |
| 406 | /* |
| 407 | * Extended attribute GET operations |
| 408 | */ |
| 409 | static ssize_t |
| 410 | getxattr(struct dentry *d, const char __user *name, void __user *value, |
| 411 | size_t size) |
| 412 | { |
| 413 | ssize_t error; |
| 414 | void *kvalue = NULL; |
| 415 | char kname[XATTR_NAME_MAX + 1]; |
| 416 | |
| 417 | error = strncpy_from_user(kname, name, sizeof(kname)); |
| 418 | if (error == 0 || error == sizeof(kname)) |
| 419 | error = -ERANGE; |
| 420 | if (error < 0) |
| 421 | return error; |
| 422 | |
| 423 | if (size) { |
| 424 | if (size > XATTR_SIZE_MAX) |
| 425 | size = XATTR_SIZE_MAX; |
| 426 | kvalue = kzalloc(size, GFP_KERNEL); |
| 427 | if (!kvalue) |
| 428 | return -ENOMEM; |
| 429 | } |
| 430 | |
| 431 | error = vfs_getxattr(d, kname, kvalue, size); |
| 432 | if (error > 0) { |
| 433 | if (size && copy_to_user(value, kvalue, error)) |
| 434 | error = -EFAULT; |
| 435 | } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) { |
| 436 | /* The file system tried to returned a value bigger |
| 437 | than XATTR_SIZE_MAX bytes. Not possible. */ |
| 438 | error = -E2BIG; |
| 439 | } |
| 440 | kfree(kvalue); |
| 441 | return error; |
| 442 | } |
| 443 | |
| 444 | SYSCALL_DEFINE4(getxattr, const char __user *, pathname, |
| 445 | const char __user *, name, void __user *, value, size_t, size) |
| 446 | { |
| 447 | struct path path; |
| 448 | ssize_t error; |
| 449 | |
| 450 | error = user_path(pathname, &path); |
| 451 | if (error) |
| 452 | return error; |
| 453 | error = getxattr(path.dentry, name, value, size); |
| 454 | path_put(&path); |
| 455 | return error; |
| 456 | } |
| 457 | |
| 458 | SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname, |
| 459 | const char __user *, name, void __user *, value, size_t, size) |
| 460 | { |
| 461 | struct path path; |
| 462 | ssize_t error; |
| 463 | |
| 464 | error = user_lpath(pathname, &path); |
| 465 | if (error) |
| 466 | return error; |
| 467 | error = getxattr(path.dentry, name, value, size); |
| 468 | path_put(&path); |
| 469 | return error; |
| 470 | } |
| 471 | |
| 472 | SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name, |
| 473 | void __user *, value, size_t, size) |
| 474 | { |
| 475 | struct file *f; |
| 476 | ssize_t error = -EBADF; |
| 477 | |
| 478 | f = fget(fd); |
| 479 | if (!f) |
| 480 | return error; |
| 481 | audit_inode(NULL, f->f_path.dentry); |
| 482 | error = getxattr(f->f_path.dentry, name, value, size); |
| 483 | fput(f); |
| 484 | return error; |
| 485 | } |
| 486 | |
| 487 | /* |
| 488 | * Extended attribute LIST operations |
| 489 | */ |
| 490 | static ssize_t |
| 491 | listxattr(struct dentry *d, char __user *list, size_t size) |
| 492 | { |
| 493 | ssize_t error; |
| 494 | char *klist = NULL; |
| 495 | |
| 496 | if (size) { |
| 497 | if (size > XATTR_LIST_MAX) |
| 498 | size = XATTR_LIST_MAX; |
| 499 | klist = kmalloc(size, GFP_KERNEL); |
| 500 | if (!klist) |
| 501 | return -ENOMEM; |
| 502 | } |
| 503 | |
| 504 | error = vfs_listxattr(d, klist, size); |
| 505 | if (error > 0) { |
| 506 | if (size && copy_to_user(list, klist, error)) |
| 507 | error = -EFAULT; |
| 508 | } else if (error == -ERANGE && size >= XATTR_LIST_MAX) { |
| 509 | /* The file system tried to returned a list bigger |
| 510 | than XATTR_LIST_MAX bytes. Not possible. */ |
| 511 | error = -E2BIG; |
| 512 | } |
| 513 | kfree(klist); |
| 514 | return error; |
| 515 | } |
| 516 | |
| 517 | SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list, |
| 518 | size_t, size) |
| 519 | { |
| 520 | struct path path; |
| 521 | ssize_t error; |
| 522 | |
| 523 | error = user_path(pathname, &path); |
| 524 | if (error) |
| 525 | return error; |
| 526 | error = listxattr(path.dentry, list, size); |
| 527 | path_put(&path); |
| 528 | return error; |
| 529 | } |
| 530 | |
| 531 | SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list, |
| 532 | size_t, size) |
| 533 | { |
| 534 | struct path path; |
| 535 | ssize_t error; |
| 536 | |
| 537 | error = user_lpath(pathname, &path); |
| 538 | if (error) |
| 539 | return error; |
| 540 | error = listxattr(path.dentry, list, size); |
| 541 | path_put(&path); |
| 542 | return error; |
| 543 | } |
| 544 | |
| 545 | SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size) |
| 546 | { |
| 547 | struct file *f; |
| 548 | ssize_t error = -EBADF; |
| 549 | |
| 550 | f = fget(fd); |
| 551 | if (!f) |
| 552 | return error; |
| 553 | audit_inode(NULL, f->f_path.dentry); |
| 554 | error = listxattr(f->f_path.dentry, list, size); |
| 555 | fput(f); |
| 556 | return error; |
| 557 | } |
| 558 | |
| 559 | /* |
| 560 | * Extended attribute REMOVE operations |
| 561 | */ |
| 562 | static long |
| 563 | removexattr(struct dentry *d, const char __user *name) |
| 564 | { |
| 565 | int error; |
| 566 | char kname[XATTR_NAME_MAX + 1]; |
| 567 | |
| 568 | error = strncpy_from_user(kname, name, sizeof(kname)); |
| 569 | if (error == 0 || error == sizeof(kname)) |
| 570 | error = -ERANGE; |
| 571 | if (error < 0) |
| 572 | return error; |
| 573 | |
| 574 | return vfs_removexattr(d, kname); |
| 575 | } |
| 576 | |
| 577 | SYSCALL_DEFINE2(removexattr, const char __user *, pathname, |
| 578 | const char __user *, name) |
| 579 | { |
| 580 | struct path path; |
| 581 | int error; |
| 582 | |
| 583 | error = user_path(pathname, &path); |
| 584 | if (error) |
| 585 | return error; |
| 586 | error = mnt_want_write(path.mnt); |
| 587 | if (!error) { |
| 588 | error = removexattr(path.dentry, name); |
| 589 | mnt_drop_write(path.mnt); |
| 590 | } |
| 591 | path_put(&path); |
| 592 | return error; |
| 593 | } |
| 594 | |
| 595 | SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname, |
| 596 | const char __user *, name) |
| 597 | { |
| 598 | struct path path; |
| 599 | int error; |
| 600 | |
| 601 | error = user_lpath(pathname, &path); |
| 602 | if (error) |
| 603 | return error; |
| 604 | error = mnt_want_write(path.mnt); |
| 605 | if (!error) { |
| 606 | error = removexattr(path.dentry, name); |
| 607 | mnt_drop_write(path.mnt); |
| 608 | } |
| 609 | path_put(&path); |
| 610 | return error; |
| 611 | } |
| 612 | |
| 613 | SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name) |
| 614 | { |
| 615 | struct file *f; |
| 616 | struct dentry *dentry; |
| 617 | int error = -EBADF; |
| 618 | |
| 619 | f = fget(fd); |
| 620 | if (!f) |
| 621 | return error; |
| 622 | dentry = f->f_path.dentry; |
| 623 | audit_inode(NULL, dentry); |
| 624 | error = mnt_want_write_file(f); |
| 625 | if (!error) { |
| 626 | error = removexattr(dentry, name); |
| 627 | mnt_drop_write(f->f_path.mnt); |
| 628 | } |
| 629 | fput(f); |
| 630 | return error; |
| 631 | } |
| 632 | |
| 633 | |
| 634 | static const char * |
| 635 | strcmp_prefix(const char *a, const char *a_prefix) |
| 636 | { |
| 637 | while (*a_prefix && *a == *a_prefix) { |
| 638 | a++; |
| 639 | a_prefix++; |
| 640 | } |
| 641 | return *a_prefix ? NULL : a; |
| 642 | } |
| 643 | |
| 644 | /* |
| 645 | * In order to implement different sets of xattr operations for each xattr |
| 646 | * prefix with the generic xattr API, a filesystem should create a |
| 647 | * null-terminated array of struct xattr_handler (one for each prefix) and |
| 648 | * hang a pointer to it off of the s_xattr field of the superblock. |
| 649 | * |
| 650 | * The generic_fooxattr() functions will use this list to dispatch xattr |
| 651 | * operations to the correct xattr_handler. |
| 652 | */ |
| 653 | #define for_each_xattr_handler(handlers, handler) \ |
| 654 | for ((handler) = *(handlers)++; \ |
| 655 | (handler) != NULL; \ |
| 656 | (handler) = *(handlers)++) |
| 657 | |
| 658 | /* |
| 659 | * Find the xattr_handler with the matching prefix. |
| 660 | */ |
| 661 | static const struct xattr_handler * |
| 662 | xattr_resolve_name(const struct xattr_handler **handlers, const char **name) |
| 663 | { |
| 664 | const struct xattr_handler *handler; |
| 665 | |
| 666 | if (!*name) |
| 667 | return NULL; |
| 668 | |
| 669 | for_each_xattr_handler(handlers, handler) { |
| 670 | const char *n = strcmp_prefix(*name, handler->prefix); |
| 671 | if (n) { |
| 672 | *name = n; |
| 673 | break; |
| 674 | } |
| 675 | } |
| 676 | return handler; |
| 677 | } |
| 678 | |
| 679 | /* |
| 680 | * Find the handler for the prefix and dispatch its get() operation. |
| 681 | */ |
| 682 | ssize_t |
| 683 | generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size) |
| 684 | { |
| 685 | const struct xattr_handler *handler; |
| 686 | |
| 687 | handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name); |
| 688 | if (!handler) |
| 689 | return -EOPNOTSUPP; |
| 690 | return handler->get(dentry, name, buffer, size, handler->flags); |
| 691 | } |
| 692 | |
| 693 | /* |
| 694 | * Combine the results of the list() operation from every xattr_handler in the |
| 695 | * list. |
| 696 | */ |
| 697 | ssize_t |
| 698 | generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size) |
| 699 | { |
| 700 | const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr; |
| 701 | unsigned int size = 0; |
| 702 | |
| 703 | if (!buffer) { |
| 704 | for_each_xattr_handler(handlers, handler) { |
| 705 | size += handler->list(dentry, NULL, 0, NULL, 0, |
| 706 | handler->flags); |
| 707 | } |
| 708 | } else { |
| 709 | char *buf = buffer; |
| 710 | |
| 711 | for_each_xattr_handler(handlers, handler) { |
| 712 | size = handler->list(dentry, buf, buffer_size, |
| 713 | NULL, 0, handler->flags); |
| 714 | if (size > buffer_size) |
| 715 | return -ERANGE; |
| 716 | buf += size; |
| 717 | buffer_size -= size; |
| 718 | } |
| 719 | size = buf - buffer; |
| 720 | } |
| 721 | return size; |
| 722 | } |
| 723 | |
| 724 | /* |
| 725 | * Find the handler for the prefix and dispatch its set() operation. |
| 726 | */ |
| 727 | int |
| 728 | generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags) |
| 729 | { |
| 730 | const struct xattr_handler *handler; |
| 731 | |
| 732 | if (size == 0) |
| 733 | value = ""; /* empty EA, do not remove */ |
| 734 | handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name); |
| 735 | if (!handler) |
| 736 | return -EOPNOTSUPP; |
| 737 | return handler->set(dentry, name, value, size, flags, handler->flags); |
| 738 | } |
| 739 | |
| 740 | /* |
| 741 | * Find the handler for the prefix and dispatch its set() operation to remove |
| 742 | * any associated extended attribute. |
| 743 | */ |
| 744 | int |
| 745 | generic_removexattr(struct dentry *dentry, const char *name) |
| 746 | { |
| 747 | const struct xattr_handler *handler; |
| 748 | |
| 749 | handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name); |
| 750 | if (!handler) |
| 751 | return -EOPNOTSUPP; |
| 752 | return handler->set(dentry, name, NULL, 0, |
| 753 | XATTR_REPLACE, handler->flags); |
| 754 | } |
| 755 | |
| 756 | EXPORT_SYMBOL(generic_getxattr); |
| 757 | EXPORT_SYMBOL(generic_listxattr); |
| 758 | EXPORT_SYMBOL(generic_setxattr); |
| 759 | EXPORT_SYMBOL(generic_removexattr); |