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
 398         error = user_lpath(pathname, &path);
 399         if (error)
 400                 return error;
 401         error = mnt_want_write(path.mnt);
 402         if (!error) {
 403                 error = setxattr(path.dentry, name, value, size, flags);
 404                 mnt_drop_write(path.mnt);
 405         }
 406         path_put(&path);
 407         return error;
 408 }
 409
 410 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 411                 const void __user *,value, size_t, size, int, flags)
 412 {
 413         struct fd f = fdget(fd);
 414         struct dentry *dentry;
 415         int error = -EBADF;
 416
 417         if (!f.file)
 418                 return error;
 419         dentry = f.file->f_path.dentry;
 420         audit_inode(NULL, dentry, 0);
 421         error = mnt_want_write_file(f.file);
 422         if (!error) {
 423                 error = setxattr(dentry, name, value, size, flags);
 424                 mnt_drop_write_file(f.file);
 425         }
 426         fdput(f);
 427         return error;
 428 }
 429
 430 /*
 431  * Extended attribute GET operations
 432  */
 433 static ssize_t
 434 getxattr(struct dentry *d, const char __user *name, void __user *value,
 435          size_t size)
 436 {
 437         ssize_t error;
 438         void *kvalue = NULL;
 439         void *vvalue = NULL;
 440         char kname[XATTR_NAME_MAX + 1];
 441
 442         error = strncpy_from_user(kname, name, sizeof(kname));
 443         if (error == 0 || error == sizeof(kname))
 444                 error = -ERANGE;
 445         if (error < 0)
 446                 return error;
 447
 448         if (size) {
 449                 if (size > XATTR_SIZE_MAX)
 450                         size = XATTR_SIZE_MAX;
 451                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 452                 if (!kvalue) {
 453                         vvalue = vmalloc(size);
 454                         if (!vvalue)
 455                                 return -ENOMEM;
 456                         kvalue = vvalue;
 457                 }
 458         }
 459
 460         error = vfs_getxattr(d, kname, kvalue, size);
 461         if (error > 0) {
 462                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 463                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 464                         posix_acl_fix_xattr_to_user(kvalue, size);
 465                 if (size && copy_to_user(value, kvalue, error))
 466                         error = -EFAULT;
 467         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 468                 /* The file system tried to returned a value bigger
 469                    than XATTR_SIZE_MAX bytes. Not possible. */
 470                 error = -E2BIG;
 471         }
 472         if (vvalue)
 473                 vfree(vvalue);
 474         else
 475                 kfree(kvalue);
 476         return error;
 477 }
 478
 479 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 480                 const char __user *, name, void __user *, value, size_t, size)
 481 {
 482         struct path path;
 483         ssize_t error;
 484
 485         error = user_path(pathname, &path);
 486         if (error)
 487                 return error;
 488         error = getxattr(path.dentry, name, value, size);
 489         path_put(&path);
 490         return error;
 491 }
 492
 493 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 494                 const char __user *, name, void __user *, value, size_t, size)
 495 {
 496         struct path path;
 497         ssize_t error;
 498
 499         error = user_lpath(pathname, &path);
 500         if (error)
 501                 return error;
 502         error = getxattr(path.dentry, name, value, size);
 503         path_put(&path);
 504         return error;
 505 }
 506
 507 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 508                 void __user *, value, size_t, size)
 509 {
 510         struct fd f = fdget(fd);
 511         ssize_t error = -EBADF;
 512
 513         if (!f.file)
 514                 return error;
 515         audit_inode(NULL, f.file->f_path.dentry, 0);
 516         error = getxattr(f.file->f_path.dentry, name, value, size);
 517         fdput(f);
 518         return error;
 519 }
 520
 521 /*
 522  * Extended attribute LIST operations
 523  */
 524 static ssize_t
 525 listxattr(struct dentry *d, char __user *list, size_t size)
 526 {
 527         ssize_t error;
 528         char *klist = NULL;
 529         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 530
 531         if (size) {
 532                 if (size > XATTR_LIST_MAX)
 533                         size = XATTR_LIST_MAX;
 534                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 535                 if (!klist) {
 536                         vlist = vmalloc(size);
 537                         if (!vlist)
 538                                 return -ENOMEM;
 539                         klist = vlist;
 540                 }
 541         }
 542
 543         error = vfs_listxattr(d, klist, size);
 544         if (error > 0) {
 545                 if (size && copy_to_user(list, klist, error))
 546                         error = -EFAULT;
 547         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 548                 /* The file system tried to returned a list bigger
 549                    than XATTR_LIST_MAX bytes. Not possible. */
 550                 error = -E2BIG;
 551         }
 552         if (vlist)
 553                 vfree(vlist);
 554         else
 555                 kfree(klist);
 556         return error;
 557 }
 558
 559 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 560                 size_t, size)
 561 {
 562         struct path path;
 563         ssize_t error;
 564
 565         error = user_path(pathname, &path);
 566         if (error)
 567                 return error;
 568         error = listxattr(path.dentry, list, size);
 569         path_put(&path);
 570         return error;
 571 }
 572
 573 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 574                 size_t, size)
 575 {
 576         struct path path;
 577         ssize_t error;
 578
 579         error = user_lpath(pathname, &path);
 580         if (error)
 581                 return error;
 582         error = listxattr(path.dentry, list, size);
 583         path_put(&path);
 584         return error;
 585 }
 586
 587 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 588 {
 589         struct fd f = fdget(fd);
 590         ssize_t error = -EBADF;
 591
 592         if (!f.file)
 593                 return error;
 594         audit_inode(NULL, f.file->f_path.dentry, 0);
 595         error = listxattr(f.file->f_path.dentry, list, size);
 596         fdput(f);
 597         return error;
 598 }
 599
 600 /*
 601  * Extended attribute REMOVE operations
 602  */
 603 static long
 604 removexattr(struct dentry *d, const char __user *name)
 605 {
 606         int error;
 607         char kname[XATTR_NAME_MAX + 1];
 608
 609         error = strncpy_from_user(kname, name, sizeof(kname));
 610         if (error == 0 || error == sizeof(kname))
 611                 error = -ERANGE;
 612         if (error < 0)
 613                 return error;
 614
 615         return vfs_removexattr(d, kname);
 616 }
 617
 618 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 619                 const char __user *, name)
 620 {
 621         struct path path;
 622         int error;
 623
 624         error = user_path(pathname, &path);
 625         if (error)
 626                 return error;
 627         error = mnt_want_write(path.mnt);
 628         if (!error) {
 629                 error = removexattr(path.dentry, name);
 630                 mnt_drop_write(path.mnt);
 631         }
 632         path_put(&path);
 633         return error;
 634 }
 635
 636 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 637                 const char __user *, name)
 638 {
 639         struct path path;
 640         int error;
 641
 642         error = user_lpath(pathname, &path);
 643         if (error)
 644                 return error;
 645         error = mnt_want_write(path.mnt);
 646         if (!error) {
 647                 error = removexattr(path.dentry, name);
 648                 mnt_drop_write(path.mnt);
 649         }
 650         path_put(&path);
 651         return error;
 652 }
 653
 654 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 655 {
 656         struct fd f = fdget(fd);
 657         struct dentry *dentry;
 658         int error = -EBADF;
 659
 660         if (!f.file)
 661                 return error;
 662         dentry = f.file->f_path.dentry;
 663         audit_inode(NULL, dentry, 0);
 664         error = mnt_want_write_file(f.file);
 665         if (!error) {
 666                 error = removexattr(dentry, name);
 667                 mnt_drop_write_file(f.file);
 668         }
 669         fdput(f);
 670         return error;
 671 }
 672
 673
 674 static const char *
 675 strcmp_prefix(const char *a, const char *a_prefix)
 676 {
 677         while (*a_prefix && *a == *a_prefix) {
 678                 a++;
 679                 a_prefix++;
 680         }
 681         return *a_prefix ? NULL : a;
 682 }
 683
 684 /*
 685  * In order to implement different sets of xattr operations for each xattr
 686  * prefix with the generic xattr API, a filesystem should create a
 687  * null-terminated array of struct xattr_handler (one for each prefix) and
 688  * hang a pointer to it off of the s_xattr field of the superblock.
 689  *
 690  * The generic_fooxattr() functions will use this list to dispatch xattr
 691  * operations to the correct xattr_handler.
 692  */
 693 #define for_each_xattr_handler(handlers, handler)               \
 694                 for ((handler) = *(handlers)++;                 \
 695                         (handler) != NULL;                      \
 696                         (handler) = *(handlers)++)
 697
 698 /*
 699  * Find the xattr_handler with the matching prefix.
 700  */
 701 static const struct xattr_handler *
 702 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 703 {
 704         const struct xattr_handler *handler;
 705
 706         if (!*name)
 707                 return NULL;
 708
 709         for_each_xattr_handler(handlers, handler) {
 710                 const char *n = strcmp_prefix(*name, handler->prefix);
 711                 if (n) {
 712                         *name = n;
 713                         break;
 714                 }
 715         }
 716         return handler;
 717 }
 718
 719 /*
 720  * Find the handler for the prefix and dispatch its get() operation.
 721  */
 722 ssize_t
 723 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 724 {
 725         const struct xattr_handler *handler;
 726
 727         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 728         if (!handler)
 729                 return -EOPNOTSUPP;
 730         return handler->get(dentry, name, buffer, size, handler->flags);
 731 }
 732
 733 /*
 734  * Combine the results of the list() operation from every xattr_handler in the
 735  * list.
 736  */
 737 ssize_t
 738 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 739 {
 740         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 741         unsigned int size = 0;
 742
 743         if (!buffer) {
 744                 for_each_xattr_handler(handlers, handler) {
 745                         size += handler->list(dentry, NULL, 0, NULL, 0,
 746                                               handler->flags);
 747                 }
 748         } else {
 749                 char *buf = buffer;
 750
 751                 for_each_xattr_handler(handlers, handler) {
 752                         size = handler->list(dentry, buf, buffer_size,
 753                                              NULL, 0, handler->flags);
 754                         if (size > buffer_size)
 755                                 return -ERANGE;
 756                         buf += size;
 757                         buffer_size -= size;
 758                 }
 759                 size = buf - buffer;
 760         }
 761         return size;
 762 }
 763
 764 /*
 765  * Find the handler for the prefix and dispatch its set() operation.
 766  */
 767 int
 768 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 769 {
 770         const struct xattr_handler *handler;
 771
 772         if (size == 0)
 773                 value = "";  /* empty EA, do not remove */
 774         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 775         if (!handler)
 776                 return -EOPNOTSUPP;
 777         return handler->set(dentry, name, value, size, flags, handler->flags);
 778 }
 779
 780 /*
 781  * Find the handler for the prefix and dispatch its set() operation to remove
 782  * any associated extended attribute.
 783  */
 784 int
 785 generic_removexattr(struct dentry *dentry, const char *name)
 786 {
 787         const struct xattr_handler *handler;
 788
 789         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 790         if (!handler)
 791                 return -EOPNOTSUPP;
 792         return handler->set(dentry, name, NULL, 0,
 793                             XATTR_REPLACE, handler->flags);
 794 }
 795
 796 EXPORT_SYMBOL(generic_getxattr);
 797 EXPORT_SYMBOL(generic_listxattr);
 798 EXPORT_SYMBOL(generic_setxattr);
 799 EXPORT_SYMBOL(generic_removexattr);
 800
 801 /*
 802  * Allocate new xattr and copy in the value; but leave the name to callers.
 803  */
 804 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 805 {
 806         struct simple_xattr *new_xattr;
 807         size_t len;
 808
 809         /* wrap around? */
 810         len = sizeof(*new_xattr) + size;
 811         if (len <= sizeof(*new_xattr))
 812                 return NULL;
 813
 814         new_xattr = kmalloc(len, GFP_KERNEL);
 815         if (!new_xattr)
 816                 return NULL;
 817
 818         new_xattr->size = size;
 819         memcpy(new_xattr->value, value, size);
 820         return new_xattr;
 821 }
 822
 823 /*
 824  * xattr GET operation for in-memory/pseudo filesystems
 825  */
 826 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 827                      void *buffer, size_t size)
 828 {
 829         struct simple_xattr *xattr;
 830         int ret = -ENODATA;
 831
 832         spin_lock(&xattrs->lock);
 833         list_for_each_entry(xattr, &xattrs->head, list) {
 834                 if (strcmp(name, xattr->name))
 835                         continue;
 836
 837                 ret = xattr->size;
 838                 if (buffer) {
 839                         if (size < xattr->size)
 840                                 ret = -ERANGE;
 841                         else
 842                                 memcpy(buffer, xattr->value, xattr->size);
 843                 }
 844                 break;
 845         }
 846         spin_unlock(&xattrs->lock);
 847         return ret;
 848 }
 849
 850 static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 851                               const void *value, size_t size, int flags)
 852 {
 853         struct simple_xattr *xattr;
 854         struct simple_xattr *new_xattr = NULL;
 855         int err = 0;
 856
 857         /* value == NULL means remove */
 858         if (value) {
 859                 new_xattr = simple_xattr_alloc(value, size);
 860                 if (!new_xattr)
 861                         return -ENOMEM;
 862
 863                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 864                 if (!new_xattr->name) {
 865                         kfree(new_xattr);
 866                         return -ENOMEM;
 867                 }
 868         }
 869
 870         spin_lock(&xattrs->lock);
 871         list_for_each_entry(xattr, &xattrs->head, list) {
 872                 if (!strcmp(name, xattr->name)) {
 873                         if (flags & XATTR_CREATE) {
 874                                 xattr = new_xattr;
 875                                 err = -EEXIST;
 876                         } else if (new_xattr) {
 877                                 list_replace(&xattr->list, &new_xattr->list);
 878                         } else {
 879                                 list_del(&xattr->list);
 880                         }
 881                         goto out;
 882                 }
 883         }
 884         if (flags & XATTR_REPLACE) {
 885                 xattr = new_xattr;
 886                 err = -ENODATA;
 887         } else {
 888                 list_add(&new_xattr->list, &xattrs->head);
 889                 xattr = NULL;
 890         }
 891 out:
 892         spin_unlock(&xattrs->lock);
 893         if (xattr) {
 894                 kfree(xattr->name);
 895                 kfree(xattr);
 896         }
 897         return err;
 898
 899 }
 900
 901 /**
 902  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 903  * @xattrs: target simple_xattr list
 904  * @name: name of the new extended attribute
 905  * @value: value of the new xattr. If %NULL, will remove the attribute
 906  * @size: size of the new xattr
 907  * @flags: %XATTR_{CREATE|REPLACE}
 908  *
 909  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 910  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 911  * otherwise, fails with -ENODATA.
 912  *
 913  * Returns 0 on success, -errno on failure.
 914  */
 915 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 916                      const void *value, size_t size, int flags)
 917 {
 918         if (size == 0)
 919                 value = ""; /* empty EA, do not remove */
 920         return __simple_xattr_set(xattrs, name, value, size, flags);
 921 }
 922
 923 /*
 924  * xattr REMOVE operation for in-memory/pseudo filesystems
 925  */
 926 int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
 927 {
 928         return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
 929 }
 930
 931 static bool xattr_is_trusted(const char *name)
 932 {
 933         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 934 }
 935
 936 /*
 937  * xattr LIST operation for in-memory/pseudo filesystems
 938  */
 939 ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
 940                           size_t size)
 941 {
 942         bool trusted = capable(CAP_SYS_ADMIN);
 943         struct simple_xattr *xattr;
 944         size_t used = 0;
 945
 946         spin_lock(&xattrs->lock);
 947         list_for_each_entry(xattr, &xattrs->head, list) {
 948                 size_t len;
 949
 950                 /* skip "trusted." attributes for unprivileged callers */
 951                 if (!trusted && xattr_is_trusted(xattr->name))
 952                         continue;
 953
 954                 len = strlen(xattr->name) + 1;
 955                 used += len;
 956                 if (buffer) {
 957                         if (size < used) {
 958                                 used = -ERANGE;
 959                                 break;
 960                         }
 961                         memcpy(buffer, xattr->name, len);
 962                         buffer += len;
 963                 }
 964         }
 965         spin_unlock(&xattrs->lock);
 966
 967         return used;
 968 }
 969
 970 /*
 971  * Adds an extended attribute to the list
 972  */
 973 void simple_xattr_list_add(struct simple_xattrs *xattrs,
 974                            struct simple_xattr *new_xattr)
 975 {
 976         spin_lock(&xattrs->lock);
 977         list_add(&new_xattr->list, &xattrs->head);
 978         spin_unlock(&xattrs->lock);
 979 }