fs/xattr.c

   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/export.h>
  20 #include <linux/fsnotify.h>
  21 #include <linux/audit.h>
  22 #include <linux/vmalloc.h>
  23 #include <linux/posix_acl_xattr.h>
  24
  25 #include <asm/uaccess.h>
  26
  27 /*
  28  * Check permissions for extended attribute access.  This is a bit complicated
  29  * because different namespaces have very different rules.
  30  */
  31 static int
  32 xattr_permission(struct inode *inode, const char *name, int mask)
  33 {
  34         /*
  35          * We can never set or remove an extended attribute on a read-only
  36          * filesystem  or on an immutable / append-only inode.
  37          */
  38         if (mask & MAY_WRITE) {
  39                 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  40                         return -EPERM;
  41         }
  42
  43         /*
  44          * No restriction for security.* and system.* from the VFS.  Decision
  45          * on these is left to the underlying filesystem / security module.
  46          */
  47         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
  48             !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  49                 return 0;
  50
  51         /*
  52          * The trusted.* namespace can only be accessed by privileged users.
  53          */
  54         if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
  55                 if (!capable(CAP_SYS_ADMIN))
  56                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  57                 return 0;
  58         }
  59
  60         /*
  61          * In the user.* namespace, only regular files and directories can have
  62          * extended attributes. For sticky directories, only the owner and
  63          * privileged users can write attributes.
  64          */
  65         if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
  66                 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
  67                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  68                 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
  69                     (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
  70                         return -EPERM;
  71         }
  72
  73         return inode_permission(inode, mask);
  74 }
  75
  76 /**
  77  *  __vfs_setxattr_noperm - perform setxattr operation without performing
  78  *  permission checks.
  79  *
  80  *  @dentry - object to perform setxattr on
  81  *  @name - xattr name to set
  82  *  @value - value to set @name to
  83  *  @size - size of @value
  84  *  @flags - flags to pass into filesystem operations
  85  *
  86  *  returns the result of the internal setxattr or setsecurity operations.
  87  *
  88  *  This function requires the caller to lock the inode's i_mutex before it
  89  *  is executed. It also assumes that the caller will make the appropriate
  90  *  permission checks.
  91  */
  92 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
  93                 const void *value, size_t size, int flags)
  94 {
  95         struct inode *inode = dentry->d_inode;
  96         int error = -EOPNOTSUPP;
  97         int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
  98                                    XATTR_SECURITY_PREFIX_LEN);
  99
 100         if (issec)
 101                 inode->i_flags &= ~S_NOSEC;
 102         if (inode->i_op->setxattr) {
 103                 error = inode->i_op->setxattr(dentry, name, value, size, flags);
 104                 if (!error) {
 105                         fsnotify_xattr(dentry);
 106                         security_inode_post_setxattr(dentry, name, value,
 107                                                      size, flags);
 108                 }
 109         } else if (issec) {
 110                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 111                 error = security_inode_setsecurity(inode, suffix, value,
 112                                                    size, flags);
 113                 if (!error)
 114                         fsnotify_xattr(dentry);
 115         }
 116
 117         return error;
 118 }
 119
 120
 121 int
 122 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 123                 size_t size, int flags)
 124 {
 125         struct inode *inode = dentry->d_inode;
 126         int error;
 127
 128         error = xattr_permission(inode, name, MAY_WRITE);
 129         if (error)
 130                 return error;
 131
 132         mutex_lock(&inode->i_mutex);
 133         error = security_inode_setxattr(dentry, name, value, size, flags);
 134         if (error)
 135                 goto out;
 136
 137         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 138
 139 out:
 140         mutex_unlock(&inode->i_mutex);
 141         return error;
 142 }
 143 EXPORT_SYMBOL_GPL(vfs_setxattr);
 144
 145 ssize_t
 146 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 147                         size_t size)
 148 {
 149         void *buffer = NULL;
 150         ssize_t len;
 151
 152         if (!value || !size) {
 153                 len = security_inode_getsecurity(inode, name, &buffer, false);
 154                 goto out_noalloc;
 155         }
 156
 157         len = security_inode_getsecurity(inode, name, &buffer, true);
 158         if (len < 0)
 159                 return len;
 160         if (size < len) {
 161                 len = -ERANGE;
 162                 goto out;
 163         }
 164         memcpy(value, buffer, len);
 165 out:
 166         security_release_secctx(buffer, len);
 167 out_noalloc:
 168         return len;
 169 }
 170 EXPORT_SYMBOL_GPL(xattr_getsecurity);
 171
 172 /*
 173  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 174  *
 175  * Allocate memory, if not already allocated, or re-allocate correct size,
 176  * before retrieving the extended attribute.
 177  *
 178  * Returns the result of alloc, if failed, or the getxattr operation.
 179  */
 180 ssize_t
 181 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 182                    size_t xattr_size, gfp_t flags)
 183 {
 184         struct inode *inode = dentry->d_inode;
 185         char *value = *xattr_value;
 186         int error;
 187
 188         error = xattr_permission(inode, name, MAY_READ);
 189         if (error)
 190                 return error;
 191
 192         if (!inode->i_op->getxattr)
 193                 return -EOPNOTSUPP;
 194
 195         error = inode->i_op->getxattr(dentry, name, NULL, 0);
 196         if (error < 0)
 197                 return error;
 198
 199         if (!value || (error > xattr_size)) {
 200                 value = krealloc(*xattr_value, error + 1, flags);
 201                 if (!value)
 202                         return -ENOMEM;
 203                 memset(value, 0, error + 1);
 204         }
 205
 206         error = inode->i_op->getxattr(dentry, name, value, error);
 207         *xattr_value = value;
 208         return error;
 209 }
 210
 211 /* Compare an extended attribute value with the given value */
 212 int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
 213                   const char *value, size_t size, gfp_t flags)
 214 {
 215         char *xattr_value = NULL;
 216         int rc;
 217
 218         rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
 219         if (rc < 0)
 220                 return rc;
 221
 222         if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
 223                 rc = -EINVAL;
 224         else
 225                 rc = 0;
 226         kfree(xattr_value);
 227         return rc;
 228 }
 229
 230 ssize_t
 231 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 232 {
 233         struct inode *inode = dentry->d_inode;
 234         int error;
 235
 236         error = xattr_permission(inode, name, MAY_READ);
 237         if (error)
 238                 return error;
 239
 240         error = security_inode_getxattr(dentry, name);
 241         if (error)
 242                 return error;
 243
 244         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 245                                 XATTR_SECURITY_PREFIX_LEN)) {
 246                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 247                 int ret = xattr_getsecurity(inode, suffix, value, size);
 248                 /*
 249                  * Only overwrite the return value if a security module
 250                  * is actually active.
 251                  */
 252                 if (ret == -EOPNOTSUPP)
 253                         goto nolsm;
 254                 return ret;
 255         }
 256 nolsm:
 257         if (inode->i_op->getxattr)
 258                 error = inode->i_op->getxattr(dentry, name, value, size);
 259         else
 260                 error = -EOPNOTSUPP;
 261
 262         return error;
 263 }
 264 EXPORT_SYMBOL_GPL(vfs_getxattr);
 265
 266 ssize_t
 267 vfs_listxattr(struct dentry *d, char *list, size_t size)
 268 {
 269         ssize_t error;
 270
 271         error = security_inode_listxattr(d);
 272         if (error)
 273                 return error;
 274         error = -EOPNOTSUPP;
 275         if (d->d_inode->i_op->listxattr) {
 276                 error = d->d_inode->i_op->listxattr(d, list, size);
 277         } else {
 278                 error = security_inode_listsecurity(d->d_inode, list, size);
 279                 if (size && error > size)
 280                         error = -ERANGE;
 281         }
 282         return error;
 283 }
 284 EXPORT_SYMBOL_GPL(vfs_listxattr);
 285
 286 int
 287 vfs_removexattr(struct dentry *dentry, const char *name)
 288 {
 289         struct inode *inode = dentry->d_inode;
 290         int error;
 291
 292         if (!inode->i_op->removexattr)
 293                 return -EOPNOTSUPP;
 294
 295         error = xattr_permission(inode, name, MAY_WRITE);
 296         if (error)
 297                 return error;
 298
 299         mutex_lock(&inode->i_mutex);
 300         error = security_inode_removexattr(dentry, name);
 301         if (error) {
 302                 mutex_unlock(&inode->i_mutex);
 303                 return error;
 304         }
 305
 306         error = inode->i_op->removexattr(dentry, name);
 307         mutex_unlock(&inode->i_mutex);
 308
 309         if (!error) {
 310                 fsnotify_xattr(dentry);
 311                 evm_inode_post_removexattr(dentry, name);
 312         }
 313         return error;
 314 }
 315 EXPORT_SYMBOL_GPL(vfs_removexattr);
 316
 317
 318 /*
 319  * Extended attribute SET operations
 320  */
 321 static long
 322 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 323          size_t size, int flags)
 324 {
 325         int error;
 326         void *kvalue = NULL;
 327         void *vvalue = NULL;    /* If non-NULL, we used vmalloc() */
 328         char kname[XATTR_NAME_MAX + 1];
 329
 330         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 331                 return -EINVAL;
 332
 333         error = strncpy_from_user(kname, name, sizeof(kname));
 334         if (error == 0 || error == sizeof(kname))
 335                 error = -ERANGE;
 336         if (error < 0)
 337                 return error;
 338
 339         if (size) {
 340                 if (size > XATTR_SIZE_MAX)
 341                         return -E2BIG;
 342                 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
 343                 if (!kvalue) {
 344                         vvalue = vmalloc(size);
 345                         if (!vvalue)
 346                                 return -ENOMEM;
 347                         kvalue = vvalue;
 348                 }
 349                 if (copy_from_user(kvalue, value, size)) {
 350                         error = -EFAULT;
 351                         goto out;
 352                 }
 353                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 354                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 355                         posix_acl_fix_xattr_from_user(kvalue, size);
 356         }
 357
 358         error = vfs_setxattr(d, kname, kvalue, size, flags);
 359 out:
 360         if (vvalue)
 361                 vfree(vvalue);
 362         else
 363                 kfree(kvalue);
 364         return error;
 365 }
 366
 367 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 368                 const char __user *, name, const void __user *, value,
 369                 size_t, size, int, flags)
 370 {
 371         struct path path;
 372         int error;
 373         unsigned int lookup_flags = LOOKUP_FOLLOW;
 374 retry:
 375         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 376         if (error)
 377                 return error;
 378         error = mnt_want_write(path.mnt);
 379         if (!error) {
 380                 error = setxattr(path.dentry, name, value, size, flags);
 381                 mnt_drop_write(path.mnt);
 382         }
 383         path_put(&path);
 384         if (retry_estale(error, lookup_flags)) {
 385                 lookup_flags |= LOOKUP_REVAL;
 386                 goto retry;
 387         }
 388         return error;
 389 }
 390
 391 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 392                 const char __user *, name, const void __user *, value,
 393                 size_t, size, int, flags)
 394 {
 395         struct path path;
 396         int error;
 397         unsigned int lookup_flags = 0;
 398 retry:
 399         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 400         if (error)
 401                 return error;
 402         error = mnt_want_write(path.mnt);
 403         if (!error) {
 404                 error = setxattr(path.dentry, name, value, size, flags);
 405                 mnt_drop_write(path.mnt);
 406         }
 407         path_put(&path);
 408         if (retry_estale(error, lookup_flags)) {
 409                 lookup_flags |= LOOKUP_REVAL;
 410                 goto retry;
 411         }
 412         return error;
 413 }
 414
 415 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 416                 const void __user *,value, size_t, size, int, flags)
 417 {
 418         struct fd f = fdget(fd);
 419         struct dentry *dentry;
 420         int error = -EBADF;
 421
 422         if (!f.file)
 423                 return error;
 424         dentry = f.file->f_path.dentry;
 425         audit_inode(NULL, dentry, 0);
 426         error = mnt_want_write_file(f.file);
 427         if (!error) {
 428                 error = setxattr(dentry, name, value, size, flags);
 429                 mnt_drop_write_file(f.file);
 430         }
 431         fdput(f);
 432         return error;
 433 }
 434
 435 /*
 436  * Extended attribute GET operations
 437  */
 438 static ssize_t
 439 getxattr(struct dentry *d, const char __user *name, void __user *value,
 440          size_t size)
 441 {
 442         ssize_t error;
 443         void *kvalue = NULL;
 444         void *vvalue = NULL;
 445         char kname[XATTR_NAME_MAX + 1];
 446
 447         error = strncpy_from_user(kname, name, sizeof(kname));
 448         if (error == 0 || error == sizeof(kname))
 449                 error = -ERANGE;
 450         if (error < 0)
 451                 return error;
 452
 453         if (size) {
 454                 if (size > XATTR_SIZE_MAX)
 455                         size = XATTR_SIZE_MAX;
 456                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 457                 if (!kvalue) {
 458                         vvalue = vmalloc(size);
 459                         if (!vvalue)
 460                                 return -ENOMEM;
 461                         kvalue = vvalue;
 462                 }
 463         }
 464
 465         error = vfs_getxattr(d, kname, kvalue, size);
 466         if (error > 0) {
 467                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 468                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 469                         posix_acl_fix_xattr_to_user(kvalue, size);
 470                 if (size && copy_to_user(value, kvalue, error))
 471                         error = -EFAULT;
 472         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 473                 /* The file system tried to returned a value bigger
 474                    than XATTR_SIZE_MAX bytes. Not possible. */
 475                 error = -E2BIG;
 476         }
 477         if (vvalue)
 478                 vfree(vvalue);
 479         else
 480                 kfree(kvalue);
 481         return error;
 482 }
 483
 484 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 485                 const char __user *, name, void __user *, value, size_t, size)
 486 {
 487         struct path path;
 488         ssize_t error;
 489         unsigned int lookup_flags = LOOKUP_FOLLOW;
 490 retry:
 491         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 492         if (error)
 493                 return error;
 494         error = getxattr(path.dentry, name, value, size);
 495         path_put(&path);
 496         if (retry_estale(error, lookup_flags)) {
 497                 lookup_flags |= LOOKUP_REVAL;
 498                 goto retry;
 499         }
 500         return error;
 501 }
 502
 503 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 504                 const char __user *, name, void __user *, value, size_t, size)
 505 {
 506         struct path path;
 507         ssize_t error;
 508         unsigned int lookup_flags = 0;
 509 retry:
 510         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 511         if (error)
 512                 return error;
 513         error = getxattr(path.dentry, name, value, size);
 514         path_put(&path);
 515         if (retry_estale(error, lookup_flags)) {
 516                 lookup_flags |= LOOKUP_REVAL;
 517                 goto retry;
 518         }
 519         return error;
 520 }
 521
 522 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 523                 void __user *, value, size_t, size)
 524 {
 525         struct fd f = fdget(fd);
 526         ssize_t error = -EBADF;
 527
 528         if (!f.file)
 529                 return error;
 530         audit_inode(NULL, f.file->f_path.dentry, 0);
 531         error = getxattr(f.file->f_path.dentry, name, value, size);
 532         fdput(f);
 533         return error;
 534 }
 535
 536 /*
 537  * Extended attribute LIST operations
 538  */
 539 static ssize_t
 540 listxattr(struct dentry *d, char __user *list, size_t size)
 541 {
 542         ssize_t error;
 543         char *klist = NULL;
 544         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 545
 546         if (size) {
 547                 if (size > XATTR_LIST_MAX)
 548                         size = XATTR_LIST_MAX;
 549                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 550                 if (!klist) {
 551                         vlist = vmalloc(size);
 552                         if (!vlist)
 553                                 return -ENOMEM;
 554                         klist = vlist;
 555                 }
 556         }
 557
 558         error = vfs_listxattr(d, klist, size);
 559         if (error > 0) {
 560                 if (size && copy_to_user(list, klist, error))
 561                         error = -EFAULT;
 562         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 563                 /* The file system tried to returned a list bigger
 564                    than XATTR_LIST_MAX bytes. Not possible. */
 565                 error = -E2BIG;
 566         }
 567         if (vlist)
 568                 vfree(vlist);
 569         else
 570                 kfree(klist);
 571         return error;
 572 }
 573
 574 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 575                 size_t, size)
 576 {
 577         struct path path;
 578         ssize_t error;
 579         unsigned int lookup_flags = LOOKUP_FOLLOW;
 580 retry:
 581         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 582         if (error)
 583                 return error;
 584         error = listxattr(path.dentry, list, size);
 585         path_put(&path);
 586         if (retry_estale(error, lookup_flags)) {
 587                 lookup_flags |= LOOKUP_REVAL;
 588                 goto retry;
 589         }
 590         return error;
 591 }
 592
 593 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 594                 size_t, size)
 595 {
 596         struct path path;
 597         ssize_t error;
 598         unsigned int lookup_flags = 0;
 599 retry:
 600         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 601         if (error)
 602                 return error;
 603         error = listxattr(path.dentry, list, size);
 604         path_put(&path);
 605         if (retry_estale(error, lookup_flags)) {
 606                 lookup_flags |= LOOKUP_REVAL;
 607                 goto retry;
 608         }
 609         return error;
 610 }
 611
 612 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 613 {
 614         struct fd f = fdget(fd);
 615         ssize_t error = -EBADF;
 616
 617         if (!f.file)
 618                 return error;
 619         audit_inode(NULL, f.file->f_path.dentry, 0);
 620         error = listxattr(f.file->f_path.dentry, list, size);
 621         fdput(f);
 622         return error;
 623 }
 624
 625 /*
 626  * Extended attribute REMOVE operations
 627  */
 628 static long
 629 removexattr(struct dentry *d, const char __user *name)
 630 {
 631         int error;
 632         char kname[XATTR_NAME_MAX + 1];
 633
 634         error = strncpy_from_user(kname, name, sizeof(kname));
 635         if (error == 0 || error == sizeof(kname))
 636                 error = -ERANGE;
 637         if (error < 0)
 638                 return error;
 639
 640         return vfs_removexattr(d, kname);
 641 }
 642
 643 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 644                 const char __user *, name)
 645 {
 646         struct path path;
 647         int error;
 648         unsigned int lookup_flags = LOOKUP_FOLLOW;
 649 retry:
 650         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 651         if (error)
 652                 return error;
 653         error = mnt_want_write(path.mnt);
 654         if (!error) {
 655                 error = removexattr(path.dentry, name);
 656                 mnt_drop_write(path.mnt);
 657         }
 658         path_put(&path);
 659         if (retry_estale(error, lookup_flags)) {
 660                 lookup_flags |= LOOKUP_REVAL;
 661                 goto retry;
 662         }
 663         return error;
 664 }
 665
 666 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 667                 const char __user *, name)
 668 {
 669         struct path path;
 670         int error;
 671         unsigned int lookup_flags = 0;
 672 retry:
 673         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 674         if (error)
 675                 return error;
 676         error = mnt_want_write(path.mnt);
 677         if (!error) {
 678                 error = removexattr(path.dentry, name);
 679                 mnt_drop_write(path.mnt);
 680         }
 681         path_put(&path);
 682         if (retry_estale(error, lookup_flags)) {
 683                 lookup_flags |= LOOKUP_REVAL;
 684                 goto retry;
 685         }
 686         return error;
 687 }
 688
 689 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 690 {
 691         struct fd f = fdget(fd);
 692         struct dentry *dentry;
 693         int error = -EBADF;
 694
 695         if (!f.file)
 696                 return error;
 697         dentry = f.file->f_path.dentry;
 698         audit_inode(NULL, dentry, 0);
 699         error = mnt_want_write_file(f.file);
 700         if (!error) {
 701                 error = removexattr(dentry, name);
 702                 mnt_drop_write_file(f.file);
 703         }
 704         fdput(f);
 705         return error;
 706 }
 707
 708
 709 static const char *
 710 strcmp_prefix(const char *a, const char *a_prefix)
 711 {
 712         while (*a_prefix && *a == *a_prefix) {
 713                 a++;
 714                 a_prefix++;
 715         }
 716         return *a_prefix ? NULL : a;
 717 }
 718
 719 /*
 720  * In order to implement different sets of xattr operations for each xattr
 721  * prefix with the generic xattr API, a filesystem should create a
 722  * null-terminated array of struct xattr_handler (one for each prefix) and
 723  * hang a pointer to it off of the s_xattr field of the superblock.
 724  *
 725  * The generic_fooxattr() functions will use this list to dispatch xattr
 726  * operations to the correct xattr_handler.
 727  */
 728 #define for_each_xattr_handler(handlers, handler)               \
 729                 for ((handler) = *(handlers)++;                 \
 730                         (handler) != NULL;                      \
 731                         (handler) = *(handlers)++)
 732
 733 /*
 734  * Find the xattr_handler with the matching prefix.
 735  */
 736 static const struct xattr_handler *
 737 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 738 {
 739         const struct xattr_handler *handler;
 740
 741         if (!*name)
 742                 return NULL;
 743
 744         for_each_xattr_handler(handlers, handler) {
 745                 const char *n = strcmp_prefix(*name, handler->prefix);
 746                 if (n) {
 747                         *name = n;
 748                         break;
 749                 }
 750         }
 751         return handler;
 752 }
 753
 754 /*
 755  * Find the handler for the prefix and dispatch its get() operation.
 756  */
 757 ssize_t
 758 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 759 {
 760         const struct xattr_handler *handler;
 761
 762         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 763         if (!handler)
 764                 return -EOPNOTSUPP;
 765         return handler->get(dentry, name, buffer, size, handler->flags);
 766 }
 767
 768 /*
 769  * Combine the results of the list() operation from every xattr_handler in the
 770  * list.
 771  */
 772 ssize_t
 773 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 774 {
 775         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 776         unsigned int size = 0;
 777
 778         if (!buffer) {
 779                 for_each_xattr_handler(handlers, handler) {
 780                         size += handler->list(dentry, NULL, 0, NULL, 0,
 781                                               handler->flags);
 782                 }
 783         } else {
 784                 char *buf = buffer;
 785
 786                 for_each_xattr_handler(handlers, handler) {
 787                         size = handler->list(dentry, buf, buffer_size,
 788                                              NULL, 0, handler->flags);
 789                         if (size > buffer_size)
 790                                 return -ERANGE;
 791                         buf += size;
 792                         buffer_size -= size;
 793                 }
 794                 size = buf - buffer;
 795         }
 796         return size;
 797 }
 798
 799 /*
 800  * Find the handler for the prefix and dispatch its set() operation.
 801  */
 802 int
 803 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 804 {
 805         const struct xattr_handler *handler;
 806
 807         if (size == 0)
 808                 value = "";  /* empty EA, do not remove */
 809         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 810         if (!handler)
 811                 return -EOPNOTSUPP;
 812         return handler->set(dentry, name, value, size, flags, handler->flags);
 813 }
 814
 815 /*
 816  * Find the handler for the prefix and dispatch its set() operation to remove
 817  * any associated extended attribute.
 818  */
 819 int
 820 generic_removexattr(struct dentry *dentry, const char *name)
 821 {
 822         const struct xattr_handler *handler;
 823
 824         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 825         if (!handler)
 826                 return -EOPNOTSUPP;
 827         return handler->set(dentry, name, NULL, 0,
 828                             XATTR_REPLACE, handler->flags);
 829 }
 830
 831 EXPORT_SYMBOL(generic_getxattr);
 832 EXPORT_SYMBOL(generic_listxattr);
 833 EXPORT_SYMBOL(generic_setxattr);
 834 EXPORT_SYMBOL(generic_removexattr);
 835
 836 /*
 837  * Allocate new xattr and copy in the value; but leave the name to callers.
 838  */
 839 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 840 {
 841         struct simple_xattr *new_xattr;
 842         size_t len;
 843
 844         /* wrap around? */
 845         len = sizeof(*new_xattr) + size;
 846         if (len < sizeof(*new_xattr))
 847                 return NULL;
 848
 849         new_xattr = kmalloc(len, GFP_KERNEL);
 850         if (!new_xattr)
 851                 return NULL;
 852
 853         new_xattr->size = size;
 854         memcpy(new_xattr->value, value, size);
 855         return new_xattr;
 856 }
 857
 858 /*
 859  * xattr GET operation for in-memory/pseudo filesystems
 860  */
 861 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 862                      void *buffer, size_t size)
 863 {
 864         struct simple_xattr *xattr;
 865         int ret = -ENODATA;
 866
 867         spin_lock(&xattrs->lock);
 868         list_for_each_entry(xattr, &xattrs->head, list) {
 869                 if (strcmp(name, xattr->name))
 870                         continue;
 871
 872                 ret = xattr->size;
 873                 if (buffer) {
 874                         if (size < xattr->size)
 875                                 ret = -ERANGE;
 876                         else
 877                                 memcpy(buffer, xattr->value, xattr->size);
 878                 }
 879                 break;
 880         }
 881         spin_unlock(&xattrs->lock);
 882         return ret;
 883 }
 884
 885 static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 886                               const void *value, size_t size, int flags)
 887 {
 888         struct simple_xattr *xattr;
 889         struct simple_xattr *new_xattr = NULL;
 890         int err = 0;
 891
 892         /* value == NULL means remove */
 893         if (value) {
 894                 new_xattr = simple_xattr_alloc(value, size);
 895                 if (!new_xattr)
 896                         return -ENOMEM;
 897
 898                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 899                 if (!new_xattr->name) {
 900                         kfree(new_xattr);
 901                         return -ENOMEM;
 902                 }
 903         }
 904
 905         spin_lock(&xattrs->lock);
 906         list_for_each_entry(xattr, &xattrs->head, list) {
 907                 if (!strcmp(name, xattr->name)) {
 908                         if (flags & XATTR_CREATE) {
 909                                 xattr = new_xattr;
 910                                 err = -EEXIST;
 911                         } else if (new_xattr) {
 912                                 list_replace(&xattr->list, &new_xattr->list);
 913                         } else {
 914                                 list_del(&xattr->list);
 915                         }
 916                         goto out;
 917                 }
 918         }
 919         if (flags & XATTR_REPLACE) {
 920                 xattr = new_xattr;
 921                 err = -ENODATA;
 922         } else {
 923                 list_add(&new_xattr->list, &xattrs->head);
 924                 xattr = NULL;
 925         }
 926 out:
 927         spin_unlock(&xattrs->lock);
 928         if (xattr) {
 929                 kfree(xattr->name);
 930                 kfree(xattr);
 931         }
 932         return err;
 933
 934 }
 935
 936 /**
 937  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 938  * @xattrs: target simple_xattr list
 939  * @name: name of the new extended attribute
 940  * @value: value of the new xattr. If %NULL, will remove the attribute
 941  * @size: size of the new xattr
 942  * @flags: %XATTR_{CREATE|REPLACE}
 943  *
 944  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 945  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 946  * otherwise, fails with -ENODATA.
 947  *
 948  * Returns 0 on success, -errno on failure.
 949  */
 950 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 951                      const void *value, size_t size, int flags)
 952 {
 953         if (size == 0)
 954                 value = ""; /* empty EA, do not remove */
 955         return __simple_xattr_set(xattrs, name, value, size, flags);
 956 }
 957
 958 /*
 959  * xattr REMOVE operation for in-memory/pseudo filesystems
 960  */
 961 int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
 962 {
 963         return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
 964 }
 965
 966 static bool xattr_is_trusted(const char *name)
 967 {
 968         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 969 }
 970
 971 /*
 972  * xattr LIST operation for in-memory/pseudo filesystems
 973  */
 974 ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
 975                           size_t size)
 976 {
 977         bool trusted = capable(CAP_SYS_ADMIN);
 978         struct simple_xattr *xattr;
 979         size_t used = 0;
 980
 981         spin_lock(&xattrs->lock);
 982         list_for_each_entry(xattr, &xattrs->head, list) {
 983                 size_t len;
 984
 985                 /* skip "trusted." attributes for unprivileged callers */
 986                 if (!trusted && xattr_is_trusted(xattr->name))
 987                         continue;
 988
 989                 len = strlen(xattr->name) + 1;
 990                 used += len;
 991                 if (buffer) {
 992                         if (size < used) {
 993                                 used = -ERANGE;
 994                                 break;
 995                         }
 996                         memcpy(buffer, xattr->name, len);
 997                         buffer += len;
 998                 }
 999         }
1000         spin_unlock(&xattrs->lock);
1001
1002         return used;
1003 }
1004
1005 /*
1006  * Adds an extended attribute to the list
1007  */
1008 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1009                            struct simple_xattr *new_xattr)
1010 {
1011         spin_lock(&xattrs->lock);
1012         list_add(&new_xattr->list, &xattrs->head);
1013         spin_unlock(&xattrs->lock);
1014 }