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