linux/fs/xattr.c
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   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
  24#include <asm/uaccess.h>
  25
  26/*
  27 * Check permissions for extended attribute access.  This is a bit complicated
  28 * because different namespaces have very different rules.
  29 */
  30static int
  31xattr_permission(struct inode *inode, const char *name, int mask)
  32{
  33        /*
  34         * We can never set or remove an extended attribute on a read-only
  35         * filesystem  or on an immutable / append-only inode.
  36         */
  37        if (mask & MAY_WRITE) {
  38                if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  39                        return -EPERM;
  40        }
  41
  42        /*
  43         * No restriction for security.* and system.* from the VFS.  Decision
  44         * on these is left to the underlying filesystem / security module.
  45         */
  46        if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
  47            !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  48                return 0;
  49
  50        /*
  51         * The trusted.* namespace can only be accessed by privileged users.
  52         */
  53        if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
  54                if (!capable(CAP_SYS_ADMIN))
  55                        return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  56                return 0;
  57        }
  58
  59        /*
  60         * In the user.* namespace, only regular files and directories can have
  61         * extended attributes. For sticky directories, only the owner and
  62         * privileged users can write attributes.
  63         */
  64        if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
  65                if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
  66                        return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  67                if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
  68                    (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
  69                        return -EPERM;
  70        }
  71
  72        return inode_permission(inode, mask);
  73}
  74
  75/**
  76 *  __vfs_setxattr_noperm - perform setxattr operation without performing
  77 *  permission checks.
  78 *
  79 *  @dentry - object to perform setxattr on
  80 *  @name - xattr name to set
  81 *  @value - value to set @name to
  82 *  @size - size of @value
  83 *  @flags - flags to pass into filesystem operations
  84 *
  85 *  returns the result of the internal setxattr or setsecurity operations.
  86 *
  87 *  This function requires the caller to lock the inode's i_mutex before it
  88 *  is executed. It also assumes that the caller will make the appropriate
  89 *  permission checks.
  90 */
  91int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
  92                const void *value, size_t size, int flags)
  93{
  94        struct inode *inode = dentry->d_inode;
  95        int error = -EOPNOTSUPP;
  96        int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
  97                                   XATTR_SECURITY_PREFIX_LEN);
  98
  99        if (issec)
 100                inode->i_flags &= ~S_NOSEC;
 101        if (inode->i_op->setxattr) {
 102                error = inode->i_op->setxattr(dentry, name, value, size, flags);
 103                if (!error) {
 104                        fsnotify_xattr(dentry);
 105                        security_inode_post_setxattr(dentry, name, value,
 106                                                     size, flags);
 107                }
 108        } else if (issec) {
 109                const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 110                error = security_inode_setsecurity(inode, suffix, value,
 111                                                   size, flags);
 112                if (!error)
 113                        fsnotify_xattr(dentry);
 114        }
 115
 116        return error;
 117}
 118
 119
 120int
 121vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 122                size_t size, int flags)
 123{
 124        struct inode *inode = dentry->d_inode;
 125        int error;
 126
 127        error = xattr_permission(inode, name, MAY_WRITE);
 128        if (error)
 129                return error;
 130
 131        mutex_lock(&inode->i_mutex);
 132        error = security_inode_setxattr(dentry, name, value, size, flags);
 133        if (error)
 134                goto out;
 135
 136        error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 137
 138out:
 139        mutex_unlock(&inode->i_mutex);
 140        return error;
 141}
 142EXPORT_SYMBOL_GPL(vfs_setxattr);
 143
 144ssize_t
 145xattr_getsecurity(struct inode *inode, const char *name, void *value,
 146                        size_t size)
 147{
 148        void *buffer = NULL;
 149        ssize_t len;
 150
 151        if (!value || !size) {
 152                len = security_inode_getsecurity(inode, name, &buffer, false);
 153                goto out_noalloc;
 154        }
 155
 156        len = security_inode_getsecurity(inode, name, &buffer, true);
 157        if (len < 0)
 158                return len;
 159        if (size < len) {
 160                len = -ERANGE;
 161                goto out;
 162        }
 163        memcpy(value, buffer, len);
 164out:
 165        security_release_secctx(buffer, len);
 166out_noalloc:
 167        return len;
 168}
 169EXPORT_SYMBOL_GPL(xattr_getsecurity);
 170
 171/*
 172 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 173 *
 174 * Allocate memory, if not already allocated, or re-allocate correct size,
 175 * before retrieving the extended attribute.
 176 *
 177 * Returns the result of alloc, if failed, or the getxattr operation.
 178 */
 179ssize_t
 180vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 181                   size_t xattr_size, gfp_t flags)
 182{
 183        struct inode *inode = dentry->d_inode;
 184        char *value = *xattr_value;
 185        int error;
 186
 187        error = xattr_permission(inode, name, MAY_READ);
 188        if (error)
 189                return error;
 190
 191        if (!inode->i_op->getxattr)
 192                return -EOPNOTSUPP;
 193
 194        error = inode->i_op->getxattr(dentry, name, NULL, 0);
 195        if (error < 0)
 196                return error;
 197
 198        if (!value || (error > xattr_size)) {
 199                value = krealloc(*xattr_value, error + 1, flags);
 200                if (!value)
 201                        return -ENOMEM;
 202                memset(value, 0, error + 1);
 203        }
 204
 205        error = inode->i_op->getxattr(dentry, name, value, error);
 206        *xattr_value = value;
 207        return error;
 208}
 209
 210/* Compare an extended attribute value with the given value */
 211int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
 212                  const char *value, size_t size, gfp_t flags)
 213{
 214        char *xattr_value = NULL;
 215        int rc;
 216
 217        rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
 218        if (rc < 0)
 219                return rc;
 220
 221        if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
 222                rc = -EINVAL;
 223        else
 224                rc = 0;
 225        kfree(xattr_value);
 226        return rc;
 227}
 228
 229ssize_t
 230vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 231{
 232        struct inode *inode = dentry->d_inode;
 233        int error;
 234
 235        error = xattr_permission(inode, name, MAY_READ);
 236        if (error)
 237                return error;
 238
 239        error = security_inode_getxattr(dentry, name);
 240        if (error)
 241                return error;
 242
 243        if (!strncmp(name, XATTR_SECURITY_PREFIX,
 244                                XATTR_SECURITY_PREFIX_LEN)) {
 245                const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 246                int ret = xattr_getsecurity(inode, suffix, value, size);
 247                /*
 248                 * Only overwrite the return value if a security module
 249                 * is actually active.
 250                 */
 251                if (ret == -EOPNOTSUPP)
 252                        goto nolsm;
 253                return ret;
 254        }
 255nolsm:
 256        if (inode->i_op->getxattr)
 257                error = inode->i_op->getxattr(dentry, name, value, size);
 258        else
 259                error = -EOPNOTSUPP;
 260
 261        return error;
 262}
 263EXPORT_SYMBOL_GPL(vfs_getxattr);
 264
 265ssize_t
 266vfs_listxattr(struct dentry *d, char *list, size_t size)
 267{
 268        ssize_t error;
 269
 270        error = security_inode_listxattr(d);
 271        if (error)
 272                return error;
 273        error = -EOPNOTSUPP;
 274        if (d->d_inode->i_op->listxattr) {
 275                error = d->d_inode->i_op->listxattr(d, list, size);
 276        } else {
 277                error = security_inode_listsecurity(d->d_inode, list, size);
 278                if (size && error > size)
 279                        error = -ERANGE;
 280        }
 281        return error;
 282}
 283EXPORT_SYMBOL_GPL(vfs_listxattr);
 284
 285int
 286vfs_removexattr(struct dentry *dentry, const char *name)
 287{
 288        struct inode *inode = dentry->d_inode;
 289        int error;
 290
 291        if (!inode->i_op->removexattr)
 292                return -EOPNOTSUPP;
 293
 294        error = xattr_permission(inode, name, MAY_WRITE);
 295        if (error)
 296                return error;
 297
 298        error = security_inode_removexattr(dentry, name);
 299        if (error)
 300                return error;
 301
 302        mutex_lock(&inode->i_mutex);
 303        error = inode->i_op->removexattr(dentry, name);
 304        mutex_unlock(&inode->i_mutex);
 305
 306        if (!error) {
 307                fsnotify_xattr(dentry);
 308                evm_inode_post_removexattr(dentry, name);
 309        }
 310        return error;
 311}
 312EXPORT_SYMBOL_GPL(vfs_removexattr);
 313
 314
 315/*
 316 * Extended attribute SET operations
 317 */
 318static long
 319setxattr(struct dentry *d, const char __user *name, const void __user *value,
 320         size_t size, int flags)
 321{
 322        int error;
 323        void *kvalue = NULL;
 324        void *vvalue = NULL;    /* If non-NULL, we used vmalloc() */
 325        char kname[XATTR_NAME_MAX + 1];
 326
 327        if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 328                return -EINVAL;
 329
 330        error = strncpy_from_user(kname, name, sizeof(kname));
 331        if (error == 0 || error == sizeof(kname))
 332                error = -ERANGE;
 333        if (error < 0)
 334                return error;
 335
 336        if (size) {
 337                if (size > XATTR_SIZE_MAX)
 338                        return -E2BIG;
 339                kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
 340                if (!kvalue) {
 341                        vvalue = vmalloc(size);
 342                        if (!vvalue)
 343                                return -ENOMEM;
 344                        kvalue = vvalue;
 345                }
 346                if (copy_from_user(kvalue, value, size)) {
 347                        error = -EFAULT;
 348                        goto out;
 349                }
 350        }
 351
 352        error = vfs_setxattr(d, kname, kvalue, size, flags);
 353out:
 354        if (vvalue)
 355                vfree(vvalue);
 356        else
 357                kfree(kvalue);
 358        return error;
 359}
 360
 361SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 362                const char __user *, name, const void __user *, value,
 363                size_t, size, int, flags)
 364{
 365        struct path path;
 366        int error;
 367
 368        error = user_path(pathname, &path);
 369        if (error)
 370                return error;
 371        error = mnt_want_write(path.mnt);
 372        if (!error) {
 373                error = setxattr(path.dentry, name, value, size, flags);
 374                mnt_drop_write(path.mnt);
 375        }
 376        path_put(&path);
 377        return error;
 378}
 379
 380SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 381                const char __user *, name, const void __user *, value,
 382                size_t, size, int, flags)
 383{
 384        struct path path;
 385        int error;
 386
 387        error = user_lpath(pathname, &path);
 388        if (error)
 389                return error;
 390        error = mnt_want_write(path.mnt);
 391        if (!error) {
 392                error = setxattr(path.dentry, name, value, size, flags);
 393                mnt_drop_write(path.mnt);
 394        }
 395        path_put(&path);
 396        return error;
 397}
 398
 399SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 400                const void __user *,value, size_t, size, int, flags)
 401{
 402        int fput_needed;
 403        struct file *f;
 404        struct dentry *dentry;
 405        int error = -EBADF;
 406
 407        f = fget_light(fd, &fput_needed);
 408        if (!f)
 409                return error;
 410        dentry = f->f_path.dentry;
 411        audit_inode(NULL, dentry);
 412        error = mnt_want_write_file(f);
 413        if (!error) {
 414                error = setxattr(dentry, name, value, size, flags);
 415                mnt_drop_write_file(f);
 416        }
 417        fput_light(f, fput_needed);
 418        return error;
 419}
 420
 421/*
 422 * Extended attribute GET operations
 423 */
 424static ssize_t
 425getxattr(struct dentry *d, const char __user *name, void __user *value,
 426         size_t size)
 427{
 428        ssize_t error;
 429        void *kvalue = NULL;
 430        void *vvalue = NULL;
 431        char kname[XATTR_NAME_MAX + 1];
 432
 433        error = strncpy_from_user(kname, name, sizeof(kname));
 434        if (error == 0 || error == sizeof(kname))
 435                error = -ERANGE;
 436        if (error < 0)
 437                return error;
 438
 439        if (size) {
 440                if (size > XATTR_SIZE_MAX)
 441                        size = XATTR_SIZE_MAX;
 442                kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 443                if (!kvalue) {
 444                        vvalue = vmalloc(size);
 445                        if (!vvalue)
 446                                return -ENOMEM;
 447                        kvalue = vvalue;
 448                }
 449        }
 450
 451        error = vfs_getxattr(d, kname, kvalue, size);
 452        if (error > 0) {
 453                if (size && copy_to_user(value, kvalue, error))
 454                        error = -EFAULT;
 455        } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 456                /* The file system tried to returned a value bigger
 457                   than XATTR_SIZE_MAX bytes. Not possible. */
 458                error = -E2BIG;
 459        }
 460        if (vvalue)
 461                vfree(vvalue);
 462        else
 463                kfree(kvalue);
 464        return error;
 465}
 466
 467SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 468                const char __user *, name, void __user *, value, size_t, size)
 469{
 470        struct path path;
 471        ssize_t error;
 472
 473        error = user_path(pathname, &path);
 474        if (error)
 475                return error;
 476        error = getxattr(path.dentry, name, value, size);
 477        path_put(&path);
 478        return error;
 479}
 480
 481SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 482                const char __user *, name, void __user *, value, size_t, size)
 483{
 484        struct path path;
 485        ssize_t error;
 486
 487        error = user_lpath(pathname, &path);
 488        if (error)
 489                return error;
 490        error = getxattr(path.dentry, name, value, size);
 491        path_put(&path);
 492        return error;
 493}
 494
 495SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 496                void __user *, value, size_t, size)
 497{
 498        int fput_needed;
 499        struct file *f;
 500        ssize_t error = -EBADF;
 501
 502        f = fget_light(fd, &fput_needed);
 503        if (!f)
 504                return error;
 505        audit_inode(NULL, f->f_path.dentry);
 506        error = getxattr(f->f_path.dentry, name, value, size);
 507        fput_light(f, fput_needed);
 508        return error;
 509}
 510
 511/*
 512 * Extended attribute LIST operations
 513 */
 514static ssize_t
 515listxattr(struct dentry *d, char __user *list, size_t size)
 516{
 517        ssize_t error;
 518        char *klist = NULL;
 519        char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 520
 521        if (size) {
 522                if (size > XATTR_LIST_MAX)
 523                        size = XATTR_LIST_MAX;
 524                klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 525                if (!klist) {
 526                        vlist = vmalloc(size);
 527                        if (!vlist)
 528                                return -ENOMEM;
 529                        klist = vlist;
 530                }
 531        }
 532
 533        error = vfs_listxattr(d, klist, size);
 534        if (error > 0) {
 535                if (size && copy_to_user(list, klist, error))
 536                        error = -EFAULT;
 537        } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 538                /* The file system tried to returned a list bigger
 539                   than XATTR_LIST_MAX bytes. Not possible. */
 540                error = -E2BIG;
 541        }
 542        if (vlist)
 543                vfree(vlist);
 544        else
 545                kfree(klist);
 546        return error;
 547}
 548
 549SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 550                size_t, size)
 551{
 552        struct path path;
 553        ssize_t error;
 554
 555        error = user_path(pathname, &path);
 556        if (error)
 557                return error;
 558        error = listxattr(path.dentry, list, size);
 559        path_put(&path);
 560        return error;
 561}
 562
 563SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 564                size_t, size)
 565{
 566        struct path path;
 567        ssize_t error;
 568
 569        error = user_lpath(pathname, &path);
 570        if (error)
 571                return error;
 572        error = listxattr(path.dentry, list, size);
 573        path_put(&path);
 574        return error;
 575}
 576
 577SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 578{
 579        int fput_needed;
 580        struct file *f;
 581        ssize_t error = -EBADF;
 582
 583        f = fget_light(fd, &fput_needed);
 584        if (!f)
 585                return error;
 586        audit_inode(NULL, f->f_path.dentry);
 587        error = listxattr(f->f_path.dentry, list, size);
 588        fput_light(f, fput_needed);
 589        return error;
 590}
 591
 592/*
 593 * Extended attribute REMOVE operations
 594 */
 595static long
 596removexattr(struct dentry *d, const char __user *name)
 597{
 598        int error;
 599        char kname[XATTR_NAME_MAX + 1];
 600
 601        error = strncpy_from_user(kname, name, sizeof(kname));
 602        if (error == 0 || error == sizeof(kname))
 603                error = -ERANGE;
 604        if (error < 0)
 605                return error;
 606
 607        return vfs_removexattr(d, kname);
 608}
 609
 610SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 611                const char __user *, name)
 612{
 613        struct path path;
 614        int error;
 615
 616        error = user_path(pathname, &path);
 617        if (error)
 618                return error;
 619        error = mnt_want_write(path.mnt);
 620        if (!error) {
 621                error = removexattr(path.dentry, name);
 622                mnt_drop_write(path.mnt);
 623        }
 624        path_put(&path);
 625        return error;
 626}
 627
 628SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 629                const char __user *, name)
 630{
 631        struct path path;
 632        int error;
 633
 634        error = user_lpath(pathname, &path);
 635        if (error)
 636                return error;
 637        error = mnt_want_write(path.mnt);
 638        if (!error) {
 639                error = removexattr(path.dentry, name);
 640                mnt_drop_write(path.mnt);
 641        }
 642        path_put(&path);
 643        return error;
 644}
 645
 646SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 647{
 648        int fput_needed;
 649        struct file *f;
 650        struct dentry *dentry;
 651        int error = -EBADF;
 652
 653        f = fget_light(fd, &fput_needed);
 654        if (!f)
 655                return error;
 656        dentry = f->f_path.dentry;
 657        audit_inode(NULL, dentry);
 658        error = mnt_want_write_file(f);
 659        if (!error) {
 660                error = removexattr(dentry, name);
 661                mnt_drop_write_file(f);
 662        }
 663        fput_light(f, fput_needed);
 664        return error;
 665}
 666
 667
 668static const char *
 669strcmp_prefix(const char *a, const char *a_prefix)
 670{
 671        while (*a_prefix && *a == *a_prefix) {
 672                a++;
 673                a_prefix++;
 674        }
 675        return *a_prefix ? NULL : a;
 676}
 677
 678/*
 679 * In order to implement different sets of xattr operations for each xattr
 680 * prefix with the generic xattr API, a filesystem should create a
 681 * null-terminated array of struct xattr_handler (one for each prefix) and
 682 * hang a pointer to it off of the s_xattr field of the superblock.
 683 *
 684 * The generic_fooxattr() functions will use this list to dispatch xattr
 685 * operations to the correct xattr_handler.
 686 */
 687#define for_each_xattr_handler(handlers, handler)               \
 688                for ((handler) = *(handlers)++;                 \
 689                        (handler) != NULL;                      \
 690                        (handler) = *(handlers)++)
 691
 692/*
 693 * Find the xattr_handler with the matching prefix.
 694 */
 695static const struct xattr_handler *
 696xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 697{
 698        const struct xattr_handler *handler;
 699
 700        if (!*name)
 701                return NULL;
 702
 703        for_each_xattr_handler(handlers, handler) {
 704                const char *n = strcmp_prefix(*name, handler->prefix);
 705                if (n) {
 706                        *name = n;
 707                        break;
 708                }
 709        }
 710        return handler;
 711}
 712
 713/*
 714 * Find the handler for the prefix and dispatch its get() operation.
 715 */
 716ssize_t
 717generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 718{
 719        const struct xattr_handler *handler;
 720
 721        handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 722        if (!handler)
 723                return -EOPNOTSUPP;
 724        return handler->get(dentry, name, buffer, size, handler->flags);
 725}
 726
 727/*
 728 * Combine the results of the list() operation from every xattr_handler in the
 729 * list.
 730 */
 731ssize_t
 732generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 733{
 734        const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 735        unsigned int size = 0;
 736
 737        if (!buffer) {
 738                for_each_xattr_handler(handlers, handler) {
 739                        size += handler->list(dentry, NULL, 0, NULL, 0,
 740                                              handler->flags);
 741                }
 742        } else {
 743                char *buf = buffer;
 744
 745                for_each_xattr_handler(handlers, handler) {
 746                        size = handler->list(dentry, buf, buffer_size,
 747                                             NULL, 0, handler->flags);
 748                        if (size > buffer_size)
 749                                return -ERANGE;
 750                        buf += size;
 751                        buffer_size -= size;
 752                }
 753                size = buf - buffer;
 754        }
 755        return size;
 756}
 757
 758/*
 759 * Find the handler for the prefix and dispatch its set() operation.
 760 */
 761int
 762generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 763{
 764        const struct xattr_handler *handler;
 765
 766        if (size == 0)
 767                value = "";  /* empty EA, do not remove */
 768        handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 769        if (!handler)
 770                return -EOPNOTSUPP;
 771        return handler->set(dentry, name, value, size, flags, handler->flags);
 772}
 773
 774/*
 775 * Find the handler for the prefix and dispatch its set() operation to remove
 776 * any associated extended attribute.
 777 */
 778int
 779generic_removexattr(struct dentry *dentry, const char *name)
 780{
 781        const struct xattr_handler *handler;
 782
 783        handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 784        if (!handler)
 785                return -EOPNOTSUPP;
 786        return handler->set(dentry, name, NULL, 0,
 787                            XATTR_REPLACE, handler->flags);
 788}
 789
 790EXPORT_SYMBOL(generic_getxattr);
 791EXPORT_SYMBOL(generic_listxattr);
 792EXPORT_SYMBOL(generic_setxattr);
 793EXPORT_SYMBOL(generic_removexattr);
 794
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