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 static int path_setxattr(const char __user *pathname,
 368                          const char __user *name, const void __user *value,
 369                          size_t size, int flags, unsigned int lookup_flags)
 370 {
 371         struct path path;
 372         int error;
 373 retry:
 374         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 375         if (error)
 376                 return error;
 377         error = mnt_want_write(path.mnt);
 378         if (!error) {
 379                 error = setxattr(path.dentry, name, value, size, flags);
 380                 mnt_drop_write(path.mnt);
 381         }
 382         path_put(&path);
 383         if (retry_estale(error, lookup_flags)) {
 384                 lookup_flags |= LOOKUP_REVAL;
 385                 goto retry;
 386         }
 387         return error;
 388 }
 389
 390 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 391                 const char __user *, name, const void __user *, value,
 392                 size_t, size, int, flags)
 393 {
 394         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 395 }
 396
 397 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 398                 const char __user *, name, const void __user *, value,
 399                 size_t, size, int, flags)
 400 {
 401         return path_setxattr(pathname, name, value, size, flags, 0);
 402 }
 403
 404 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 405                 const void __user *,value, size_t, size, int, flags)
 406 {
 407         struct fd f = fdget(fd);
 408         struct dentry *dentry;
 409         int error = -EBADF;
 410
 411         if (!f.file)
 412                 return error;
 413         dentry = f.file->f_path.dentry;
 414         audit_inode(NULL, dentry, 0);
 415         error = mnt_want_write_file(f.file);
 416         if (!error) {
 417                 error = setxattr(dentry, name, value, size, flags);
 418                 mnt_drop_write_file(f.file);
 419         }
 420         fdput(f);
 421         return error;
 422 }
 423
 424 /*
 425  * Extended attribute GET operations
 426  */
 427 static ssize_t
 428 getxattr(struct dentry *d, const char __user *name, void __user *value,
 429          size_t size)
 430 {
 431         ssize_t error;
 432         void *kvalue = NULL;
 433         void *vvalue = NULL;
 434         char kname[XATTR_NAME_MAX + 1];
 435
 436         error = strncpy_from_user(kname, name, sizeof(kname));
 437         if (error == 0 || error == sizeof(kname))
 438                 error = -ERANGE;
 439         if (error < 0)
 440                 return error;
 441
 442         if (size) {
 443                 if (size > XATTR_SIZE_MAX)
 444                         size = XATTR_SIZE_MAX;
 445                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 446                 if (!kvalue) {
 447                         vvalue = vmalloc(size);
 448                         if (!vvalue)
 449                                 return -ENOMEM;
 450                         kvalue = vvalue;
 451                 }
 452         }
 453
 454         error = vfs_getxattr(d, kname, kvalue, size);
 455         if (error > 0) {
 456                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 457                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 458                         posix_acl_fix_xattr_to_user(kvalue, size);
 459                 if (size && copy_to_user(value, kvalue, error))
 460                         error = -EFAULT;
 461         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 462                 /* The file system tried to returned a value bigger
 463                    than XATTR_SIZE_MAX bytes. Not possible. */
 464                 error = -E2BIG;
 465         }
 466         if (vvalue)
 467                 vfree(vvalue);
 468         else
 469                 kfree(kvalue);
 470         return error;
 471 }
 472
 473 static ssize_t path_getxattr(const char __user *pathname,
 474                              const char __user *name, void __user *value,
 475                              size_t size, unsigned int lookup_flags)
 476 {
 477         struct path path;
 478         ssize_t error;
 479 retry:
 480         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 481         if (error)
 482                 return error;
 483         error = getxattr(path.dentry, name, value, size);
 484         path_put(&path);
 485         if (retry_estale(error, lookup_flags)) {
 486                 lookup_flags |= LOOKUP_REVAL;
 487                 goto retry;
 488         }
 489         return error;
 490 }
 491
 492 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 493                 const char __user *, name, void __user *, value, size_t, size)
 494 {
 495         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 496 }
 497
 498 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 499                 const char __user *, name, void __user *, value, size_t, size)
 500 {
 501         return path_getxattr(pathname, name, value, size, 0);
 502 }
 503
 504 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 505                 void __user *, value, size_t, size)
 506 {
 507         struct fd f = fdget(fd);
 508         ssize_t error = -EBADF;
 509
 510         if (!f.file)
 511                 return error;
 512         audit_inode(NULL, f.file->f_path.dentry, 0);
 513         error = getxattr(f.file->f_path.dentry, name, value, size);
 514         fdput(f);
 515         return error;
 516 }
 517
 518 /*
 519  * Extended attribute LIST operations
 520  */
 521 static ssize_t
 522 listxattr(struct dentry *d, char __user *list, size_t size)
 523 {
 524         ssize_t error;
 525         char *klist = NULL;
 526         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 527
 528         if (size) {
 529                 if (size > XATTR_LIST_MAX)
 530                         size = XATTR_LIST_MAX;
 531                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 532                 if (!klist) {
 533                         vlist = vmalloc(size);
 534                         if (!vlist)
 535                                 return -ENOMEM;
 536                         klist = vlist;
 537                 }
 538         }
 539
 540         error = vfs_listxattr(d, klist, size);
 541         if (error > 0) {
 542                 if (size && copy_to_user(list, klist, error))
 543                         error = -EFAULT;
 544         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 545                 /* The file system tried to returned a list bigger
 546                    than XATTR_LIST_MAX bytes. Not possible. */
 547                 error = -E2BIG;
 548         }
 549         if (vlist)
 550                 vfree(vlist);
 551         else
 552                 kfree(klist);
 553         return error;
 554 }
 555
 556 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 557                               size_t size, unsigned int lookup_flags)
 558 {
 559         struct path path;
 560         ssize_t error;
 561 retry:
 562         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 563         if (error)
 564                 return error;
 565         error = listxattr(path.dentry, list, size);
 566         path_put(&path);
 567         if (retry_estale(error, lookup_flags)) {
 568                 lookup_flags |= LOOKUP_REVAL;
 569                 goto retry;
 570         }
 571         return error;
 572 }
 573
 574 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 575                 size_t, size)
 576 {
 577         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 578 }
 579
 580 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 581                 size_t, size)
 582 {
 583         return path_listxattr(pathname, list, size, 0);
 584 }
 585
 586 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 587 {
 588         struct fd f = fdget(fd);
 589         ssize_t error = -EBADF;
 590
 591         if (!f.file)
 592                 return error;
 593         audit_inode(NULL, f.file->f_path.dentry, 0);
 594         error = listxattr(f.file->f_path.dentry, list, size);
 595         fdput(f);
 596         return error;
 597 }
 598
 599 /*
 600  * Extended attribute REMOVE operations
 601  */
 602 static long
 603 removexattr(struct dentry *d, const char __user *name)
 604 {
 605         int error;
 606         char kname[XATTR_NAME_MAX + 1];
 607
 608         error = strncpy_from_user(kname, name, sizeof(kname));
 609         if (error == 0 || error == sizeof(kname))
 610                 error = -ERANGE;
 611         if (error < 0)
 612                 return error;
 613
 614         return vfs_removexattr(d, kname);
 615 }
 616
 617 static int path_removexattr(const char __user *pathname,
 618                             const char __user *name, unsigned int lookup_flags)
 619 {
 620         struct path path;
 621         int error;
 622 retry:
 623         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 624         if (error)
 625                 return error;
 626         error = mnt_want_write(path.mnt);
 627         if (!error) {
 628                 error = removexattr(path.dentry, name);
 629                 mnt_drop_write(path.mnt);
 630         }
 631         path_put(&path);
 632         if (retry_estale(error, lookup_flags)) {
 633                 lookup_flags |= LOOKUP_REVAL;
 634                 goto retry;
 635         }
 636         return error;
 637 }
 638
 639 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 640                 const char __user *, name)
 641 {
 642         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 643 }
 644
 645 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 646                 const char __user *, name)
 647 {
 648         return path_removexattr(pathname, name, 0);
 649 }
 650
 651 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 652 {
 653         struct fd f = fdget(fd);
 654         struct dentry *dentry;
 655         int error = -EBADF;
 656
 657         if (!f.file)
 658                 return error;
 659         dentry = f.file->f_path.dentry;
 660         audit_inode(NULL, dentry, 0);
 661         error = mnt_want_write_file(f.file);
 662         if (!error) {
 663                 error = removexattr(dentry, name);
 664                 mnt_drop_write_file(f.file);
 665         }
 666         fdput(f);
 667         return error;
 668 }
 669
 670
 671 static const char *
 672 strcmp_prefix(const char *a, const char *a_prefix)
 673 {
 674         while (*a_prefix && *a == *a_prefix) {
 675                 a++;
 676                 a_prefix++;
 677         }
 678         return *a_prefix ? NULL : a;
 679 }
 680
 681 /*
 682  * In order to implement different sets of xattr operations for each xattr
 683  * prefix with the generic xattr API, a filesystem should create a
 684  * null-terminated array of struct xattr_handler (one for each prefix) and
 685  * hang a pointer to it off of the s_xattr field of the superblock.
 686  *
 687  * The generic_fooxattr() functions will use this list to dispatch xattr
 688  * operations to the correct xattr_handler.
 689  */
 690 #define for_each_xattr_handler(handlers, handler)               \
 691                 for ((handler) = *(handlers)++;                 \
 692                         (handler) != NULL;                      \
 693                         (handler) = *(handlers)++)
 694
 695 /*
 696  * Find the xattr_handler with the matching prefix.
 697  */
 698 static const struct xattr_handler *
 699 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 700 {
 701         const struct xattr_handler *handler;
 702
 703         if (!*name)
 704                 return NULL;
 705
 706         for_each_xattr_handler(handlers, handler) {
 707                 const char *n = strcmp_prefix(*name, handler->prefix);
 708                 if (n) {
 709                         *name = n;
 710                         break;
 711                 }
 712         }
 713         return handler;
 714 }
 715
 716 /*
 717  * Find the handler for the prefix and dispatch its get() operation.
 718  */
 719 ssize_t
 720 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 721 {
 722         const struct xattr_handler *handler;
 723
 724         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 725         if (!handler)
 726                 return -EOPNOTSUPP;
 727         return handler->get(dentry, name, buffer, size, handler->flags);
 728 }
 729
 730 /*
 731  * Combine the results of the list() operation from every xattr_handler in the
 732  * list.
 733  */
 734 ssize_t
 735 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 736 {
 737         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 738         unsigned int size = 0;
 739
 740         if (!buffer) {
 741                 for_each_xattr_handler(handlers, handler) {
 742                         size += handler->list(dentry, NULL, 0, NULL, 0,
 743                                               handler->flags);
 744                 }
 745         } else {
 746                 char *buf = buffer;
 747
 748                 for_each_xattr_handler(handlers, handler) {
 749                         size = handler->list(dentry, buf, buffer_size,
 750                                              NULL, 0, handler->flags);
 751                         if (size > buffer_size)
 752                                 return -ERANGE;
 753                         buf += size;
 754                         buffer_size -= size;
 755                 }
 756                 size = buf - buffer;
 757         }
 758         return size;
 759 }
 760
 761 /*
 762  * Find the handler for the prefix and dispatch its set() operation.
 763  */
 764 int
 765 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 766 {
 767         const struct xattr_handler *handler;
 768
 769         if (size == 0)
 770                 value = "";  /* empty EA, do not remove */
 771         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 772         if (!handler)
 773                 return -EOPNOTSUPP;
 774         return handler->set(dentry, name, value, size, flags, handler->flags);
 775 }
 776
 777 /*
 778  * Find the handler for the prefix and dispatch its set() operation to remove
 779  * any associated extended attribute.
 780  */
 781 int
 782 generic_removexattr(struct dentry *dentry, const char *name)
 783 {
 784         const struct xattr_handler *handler;
 785
 786         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 787         if (!handler)
 788                 return -EOPNOTSUPP;
 789         return handler->set(dentry, name, NULL, 0,
 790                             XATTR_REPLACE, handler->flags);
 791 }
 792
 793 EXPORT_SYMBOL(generic_getxattr);
 794 EXPORT_SYMBOL(generic_listxattr);
 795 EXPORT_SYMBOL(generic_setxattr);
 796 EXPORT_SYMBOL(generic_removexattr);
 797
 798 /*
 799  * Allocate new xattr and copy in the value; but leave the name to callers.
 800  */
 801 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 802 {
 803         struct simple_xattr *new_xattr;
 804         size_t len;
 805
 806         /* wrap around? */
 807         len = sizeof(*new_xattr) + size;
 808         if (len < sizeof(*new_xattr))
 809                 return NULL;
 810
 811         new_xattr = kmalloc(len, GFP_KERNEL);
 812         if (!new_xattr)
 813                 return NULL;
 814
 815         new_xattr->size = size;
 816         memcpy(new_xattr->value, value, size);
 817         return new_xattr;
 818 }
 819
 820 /*
 821  * xattr GET operation for in-memory/pseudo filesystems
 822  */
 823 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 824                      void *buffer, size_t size)
 825 {
 826         struct simple_xattr *xattr;
 827         int ret = -ENODATA;
 828
 829         spin_lock(&xattrs->lock);
 830         list_for_each_entry(xattr, &xattrs->head, list) {
 831                 if (strcmp(name, xattr->name))
 832                         continue;
 833
 834                 ret = xattr->size;
 835                 if (buffer) {
 836                         if (size < xattr->size)
 837                                 ret = -ERANGE;
 838                         else
 839                                 memcpy(buffer, xattr->value, xattr->size);
 840                 }
 841                 break;
 842         }
 843         spin_unlock(&xattrs->lock);
 844         return ret;
 845 }
 846
 847 static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 848                               const void *value, size_t size, int flags)
 849 {
 850         struct simple_xattr *xattr;
 851         struct simple_xattr *new_xattr = NULL;
 852         int err = 0;
 853
 854         /* value == NULL means remove */
 855         if (value) {
 856                 new_xattr = simple_xattr_alloc(value, size);
 857                 if (!new_xattr)
 858                         return -ENOMEM;
 859
 860                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 861                 if (!new_xattr->name) {
 862                         kfree(new_xattr);
 863                         return -ENOMEM;
 864                 }
 865         }
 866
 867         spin_lock(&xattrs->lock);
 868         list_for_each_entry(xattr, &xattrs->head, list) {
 869                 if (!strcmp(name, xattr->name)) {
 870                         if (flags & XATTR_CREATE) {
 871                                 xattr = new_xattr;
 872                                 err = -EEXIST;
 873                         } else if (new_xattr) {
 874                                 list_replace(&xattr->list, &new_xattr->list);
 875                         } else {
 876                                 list_del(&xattr->list);
 877                         }
 878                         goto out;
 879                 }
 880         }
 881         if (flags & XATTR_REPLACE) {
 882                 xattr = new_xattr;
 883                 err = -ENODATA;
 884         } else {
 885                 list_add(&new_xattr->list, &xattrs->head);
 886                 xattr = NULL;
 887         }
 888 out:
 889         spin_unlock(&xattrs->lock);
 890         if (xattr) {
 891                 kfree(xattr->name);
 892                 kfree(xattr);
 893         }
 894         return err;
 895
 896 }
 897
 898 /**
 899  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 900  * @xattrs: target simple_xattr list
 901  * @name: name of the new extended attribute
 902  * @value: value of the new xattr. If %NULL, will remove the attribute
 903  * @size: size of the new xattr
 904  * @flags: %XATTR_{CREATE|REPLACE}
 905  *
 906  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 907  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 908  * otherwise, fails with -ENODATA.
 909  *
 910  * Returns 0 on success, -errno on failure.
 911  */
 912 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 913                      const void *value, size_t size, int flags)
 914 {
 915         if (size == 0)
 916                 value = ""; /* empty EA, do not remove */
 917         return __simple_xattr_set(xattrs, name, value, size, flags);
 918 }
 919
 920 /*
 921  * xattr REMOVE operation for in-memory/pseudo filesystems
 922  */
 923 int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
 924 {
 925         return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
 926 }
 927
 928 static bool xattr_is_trusted(const char *name)
 929 {
 930         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 931 }
 932
 933 /*
 934  * xattr LIST operation for in-memory/pseudo filesystems
 935  */
 936 ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
 937                           size_t size)
 938 {
 939         bool trusted = capable(CAP_SYS_ADMIN);
 940         struct simple_xattr *xattr;
 941         size_t used = 0;
 942
 943         spin_lock(&xattrs->lock);
 944         list_for_each_entry(xattr, &xattrs->head, list) {
 945                 size_t len;
 946
 947                 /* skip "trusted." attributes for unprivileged callers */
 948                 if (!trusted && xattr_is_trusted(xattr->name))
 949                         continue;
 950
 951                 len = strlen(xattr->name) + 1;
 952                 used += len;
 953                 if (buffer) {
 954                         if (size < used) {
 955                                 used = -ERANGE;
 956                                 break;
 957                         }
 958                         memcpy(buffer, xattr->name, len);
 959                         buffer += len;
 960                 }
 961         }
 962         spin_unlock(&xattrs->lock);
 963
 964         return used;
 965 }
 966
 967 /*
 968  * Adds an extended attribute to the list
 969  */
 970 void simple_xattr_list_add(struct simple_xattrs *xattrs,
 971                            struct simple_xattr *new_xattr)
 972 {
 973         spin_lock(&xattrs->lock);
 974         list_add(&new_xattr->list, &xattrs->head);
 975         spin_unlock(&xattrs->lock);
 976 }