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