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
 580         error = user_path(pathname, &path);
 581         if (error)
 582                 return error;
 583         error = listxattr(path.dentry, list, size);
 584         path_put(&path);
 585         return error;
 586 }
 587
 588 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 589                 size_t, size)
 590 {
 591         struct path path;
 592         ssize_t error;
 593
 594         error = user_lpath(pathname, &path);
 595         if (error)
 596                 return error;
 597         error = listxattr(path.dentry, list, size);
 598         path_put(&path);
 599         return error;
 600 }
 601
 602 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 603 {
 604         struct fd f = fdget(fd);
 605         ssize_t error = -EBADF;
 606
 607         if (!f.file)
 608                 return error;
 609         audit_inode(NULL, f.file->f_path.dentry, 0);
 610         error = listxattr(f.file->f_path.dentry, list, size);
 611         fdput(f);
 612         return error;
 613 }
 614
 615 /*
 616  * Extended attribute REMOVE operations
 617  */
 618 static long
 619 removexattr(struct dentry *d, const char __user *name)
 620 {
 621         int error;
 622         char kname[XATTR_NAME_MAX + 1];
 623
 624         error = strncpy_from_user(kname, name, sizeof(kname));
 625         if (error == 0 || error == sizeof(kname))
 626                 error = -ERANGE;
 627         if (error < 0)
 628                 return error;
 629
 630         return vfs_removexattr(d, kname);
 631 }
 632
 633 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 634                 const char __user *, name)
 635 {
 636         struct path path;
 637         int error;
 638
 639         error = user_path(pathname, &path);
 640         if (error)
 641                 return error;
 642         error = mnt_want_write(path.mnt);
 643         if (!error) {
 644                 error = removexattr(path.dentry, name);
 645                 mnt_drop_write(path.mnt);
 646         }
 647         path_put(&path);
 648         return error;
 649 }
 650
 651 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 652                 const char __user *, name)
 653 {
 654         struct path path;
 655         int error;
 656
 657         error = user_lpath(pathname, &path);
 658         if (error)
 659                 return error;
 660         error = mnt_want_write(path.mnt);
 661         if (!error) {
 662                 error = removexattr(path.dentry, name);
 663                 mnt_drop_write(path.mnt);
 664         }
 665         path_put(&path);
 666         return error;
 667 }
 668
 669 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 670 {
 671         struct fd f = fdget(fd);
 672         struct dentry *dentry;
 673         int error = -EBADF;
 674
 675         if (!f.file)
 676                 return error;
 677         dentry = f.file->f_path.dentry;
 678         audit_inode(NULL, dentry, 0);
 679         error = mnt_want_write_file(f.file);
 680         if (!error) {
 681                 error = removexattr(dentry, name);
 682                 mnt_drop_write_file(f.file);
 683         }
 684         fdput(f);
 685         return error;
 686 }
 687
 688
 689 static const char *
 690 strcmp_prefix(const char *a, const char *a_prefix)
 691 {
 692         while (*a_prefix && *a == *a_prefix) {
 693                 a++;
 694                 a_prefix++;
 695         }
 696         return *a_prefix ? NULL : a;
 697 }
 698
 699 /*
 700  * In order to implement different sets of xattr operations for each xattr
 701  * prefix with the generic xattr API, a filesystem should create a
 702  * null-terminated array of struct xattr_handler (one for each prefix) and
 703  * hang a pointer to it off of the s_xattr field of the superblock.
 704  *
 705  * The generic_fooxattr() functions will use this list to dispatch xattr
 706  * operations to the correct xattr_handler.
 707  */
 708 #define for_each_xattr_handler(handlers, handler)               \
 709                 for ((handler) = *(handlers)++;                 \
 710                         (handler) != NULL;                      \
 711                         (handler) = *(handlers)++)
 712
 713 /*
 714  * Find the xattr_handler with the matching prefix.
 715  */
 716 static const struct xattr_handler *
 717 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 718 {
 719         const struct xattr_handler *handler;
 720
 721         if (!*name)
 722                 return NULL;
 723
 724         for_each_xattr_handler(handlers, handler) {
 725                 const char *n = strcmp_prefix(*name, handler->prefix);
 726                 if (n) {
 727                         *name = n;
 728                         break;
 729                 }
 730         }
 731         return handler;
 732 }
 733
 734 /*
 735  * Find the handler for the prefix and dispatch its get() operation.
 736  */
 737 ssize_t
 738 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 739 {
 740         const struct xattr_handler *handler;
 741
 742         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 743         if (!handler)
 744                 return -EOPNOTSUPP;
 745         return handler->get(dentry, name, buffer, size, handler->flags);
 746 }
 747
 748 /*
 749  * Combine the results of the list() operation from every xattr_handler in the
 750  * list.
 751  */
 752 ssize_t
 753 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 754 {
 755         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 756         unsigned int size = 0;
 757
 758         if (!buffer) {
 759                 for_each_xattr_handler(handlers, handler) {
 760                         size += handler->list(dentry, NULL, 0, NULL, 0,
 761                                               handler->flags);
 762                 }
 763         } else {
 764                 char *buf = buffer;
 765
 766                 for_each_xattr_handler(handlers, handler) {
 767                         size = handler->list(dentry, buf, buffer_size,
 768                                              NULL, 0, handler->flags);
 769                         if (size > buffer_size)
 770                                 return -ERANGE;
 771                         buf += size;
 772                         buffer_size -= size;
 773                 }
 774                 size = buf - buffer;
 775         }
 776         return size;
 777 }
 778
 779 /*
 780  * Find the handler for the prefix and dispatch its set() operation.
 781  */
 782 int
 783 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 784 {
 785         const struct xattr_handler *handler;
 786
 787         if (size == 0)
 788                 value = "";  /* empty EA, do not remove */
 789         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 790         if (!handler)
 791                 return -EOPNOTSUPP;
 792         return handler->set(dentry, name, value, size, flags, handler->flags);
 793 }
 794
 795 /*
 796  * Find the handler for the prefix and dispatch its set() operation to remove
 797  * any associated extended attribute.
 798  */
 799 int
 800 generic_removexattr(struct dentry *dentry, const char *name)
 801 {
 802         const struct xattr_handler *handler;
 803
 804         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 805         if (!handler)
 806                 return -EOPNOTSUPP;
 807         return handler->set(dentry, name, NULL, 0,
 808                             XATTR_REPLACE, handler->flags);
 809 }
 810
 811 EXPORT_SYMBOL(generic_getxattr);
 812 EXPORT_SYMBOL(generic_listxattr);
 813 EXPORT_SYMBOL(generic_setxattr);
 814 EXPORT_SYMBOL(generic_removexattr);
 815
 816 /*
 817  * Allocate new xattr and copy in the value; but leave the name to callers.
 818  */
 819 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 820 {
 821         struct simple_xattr *new_xattr;
 822         size_t len;
 823
 824         /* wrap around? */
 825         len = sizeof(*new_xattr) + size;
 826         if (len <= sizeof(*new_xattr))
 827                 return NULL;
 828
 829         new_xattr = kmalloc(len, GFP_KERNEL);
 830         if (!new_xattr)
 831                 return NULL;
 832
 833         new_xattr->size = size;
 834         memcpy(new_xattr->value, value, size);
 835         return new_xattr;
 836 }
 837
 838 /*
 839  * xattr GET operation for in-memory/pseudo filesystems
 840  */
 841 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 842                      void *buffer, size_t size)
 843 {
 844         struct simple_xattr *xattr;
 845         int ret = -ENODATA;
 846
 847         spin_lock(&xattrs->lock);
 848         list_for_each_entry(xattr, &xattrs->head, list) {
 849                 if (strcmp(name, xattr->name))
 850                         continue;
 851
 852                 ret = xattr->size;
 853                 if (buffer) {
 854                         if (size < xattr->size)
 855                                 ret = -ERANGE;
 856                         else
 857                                 memcpy(buffer, xattr->value, xattr->size);
 858                 }
 859                 break;
 860         }
 861         spin_unlock(&xattrs->lock);
 862         return ret;
 863 }
 864
 865 static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 866                               const void *value, size_t size, int flags)
 867 {
 868         struct simple_xattr *xattr;
 869         struct simple_xattr *new_xattr = NULL;
 870         int err = 0;
 871
 872         /* value == NULL means remove */
 873         if (value) {
 874                 new_xattr = simple_xattr_alloc(value, size);
 875                 if (!new_xattr)
 876                         return -ENOMEM;
 877
 878                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 879                 if (!new_xattr->name) {
 880                         kfree(new_xattr);
 881                         return -ENOMEM;
 882                 }
 883         }
 884
 885         spin_lock(&xattrs->lock);
 886         list_for_each_entry(xattr, &xattrs->head, list) {
 887                 if (!strcmp(name, xattr->name)) {
 888                         if (flags & XATTR_CREATE) {
 889                                 xattr = new_xattr;
 890                                 err = -EEXIST;
 891                         } else if (new_xattr) {
 892                                 list_replace(&xattr->list, &new_xattr->list);
 893                         } else {
 894                                 list_del(&xattr->list);
 895                         }
 896                         goto out;
 897                 }
 898         }
 899         if (flags & XATTR_REPLACE) {
 900                 xattr = new_xattr;
 901                 err = -ENODATA;
 902         } else {
 903                 list_add(&new_xattr->list, &xattrs->head);
 904                 xattr = NULL;
 905         }
 906 out:
 907         spin_unlock(&xattrs->lock);
 908         if (xattr) {
 909                 kfree(xattr->name);
 910                 kfree(xattr);
 911         }
 912         return err;
 913
 914 }
 915
 916 /**
 917  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 918  * @xattrs: target simple_xattr list
 919  * @name: name of the new extended attribute
 920  * @value: value of the new xattr. If %NULL, will remove the attribute
 921  * @size: size of the new xattr
 922  * @flags: %XATTR_{CREATE|REPLACE}
 923  *
 924  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 925  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 926  * otherwise, fails with -ENODATA.
 927  *
 928  * Returns 0 on success, -errno on failure.
 929  */
 930 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 931                      const void *value, size_t size, int flags)
 932 {
 933         if (size == 0)
 934                 value = ""; /* empty EA, do not remove */
 935         return __simple_xattr_set(xattrs, name, value, size, flags);
 936 }
 937
 938 /*
 939  * xattr REMOVE operation for in-memory/pseudo filesystems
 940  */
 941 int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
 942 {
 943         return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
 944 }
 945
 946 static bool xattr_is_trusted(const char *name)
 947 {
 948         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 949 }
 950
 951 /*
 952  * xattr LIST operation for in-memory/pseudo filesystems
 953  */
 954 ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
 955                           size_t size)
 956 {
 957         bool trusted = capable(CAP_SYS_ADMIN);
 958         struct simple_xattr *xattr;
 959         size_t used = 0;
 960
 961         spin_lock(&xattrs->lock);
 962         list_for_each_entry(xattr, &xattrs->head, list) {
 963                 size_t len;
 964
 965                 /* skip "trusted." attributes for unprivileged callers */
 966                 if (!trusted && xattr_is_trusted(xattr->name))
 967                         continue;
 968
 969                 len = strlen(xattr->name) + 1;
 970                 used += len;
 971                 if (buffer) {
 972                         if (size < used) {
 973                                 used = -ERANGE;
 974                                 break;
 975                         }
 976                         memcpy(buffer, xattr->name, len);
 977                         buffer += len;
 978                 }
 979         }
 980         spin_unlock(&xattrs->lock);
 981
 982         return used;
 983 }
 984
 985 /*
 986  * Adds an extended attribute to the list
 987  */
 988 void simple_xattr_list_add(struct simple_xattrs *xattrs,
 989                            struct simple_xattr *new_xattr)
 990 {
 991         spin_lock(&xattrs->lock);
 992         list_add(&new_xattr->list, &xattrs->head);
 993         spin_unlock(&xattrs->lock);
 994 }