linux/fs/xattr.c
<<
>>
Prefs
   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 */
  31static int
  32xattr_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 */
  92int __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
 121int
 122vfs_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
 139out:
 140        mutex_unlock(&inode->i_mutex);
 141        return error;
 142}
 143EXPORT_SYMBOL_GPL(vfs_setxattr);
 144
 145ssize_t
 146xattr_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);
 165out:
 166        security_release_secctx(buffer, len);
 167out_noalloc:
 168        return len;
 169}
 170EXPORT_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 */
 180ssize_t
 181vfs_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 */
 212int 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
 230ssize_t
 231vfs_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        }
 256nolsm:
 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}
 264EXPORT_SYMBOL_GPL(vfs_getxattr);
 265
 266ssize_t
 267vfs_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}
 284EXPORT_SYMBOL_GPL(vfs_listxattr);
 285
 286int
 287vfs_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}
 315EXPORT_SYMBOL_GPL(vfs_removexattr);
 316
 317
 318/*
 319 * Extended attribute SET operations
 320 */
 321static long
 322setxattr(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);
 359out:
 360        if (vvalue)
 361                vfree(vvalue);
 362        else
 363                kfree(kvalue);
 364        return error;
 365}
 366
 367SYSCALL_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
 386SYSCALL_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
 405SYSCALL_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 */
 428static ssize_t
 429getxattr(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
 474SYSCALL_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
 488SYSCALL_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
 502SYSCALL_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 */
 519static ssize_t
 520listxattr(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
 554SYSCALL_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
 568SYSCALL_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
 582SYSCALL_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 */
 598static long
 599removexattr(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
 613SYSCALL_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
 631SYSCALL_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
 649SYSCALL_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
 669static const char *
 670strcmp_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 */
 696static const struct xattr_handler *
 697xattr_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 */
 717ssize_t
 718generic_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 */
 732ssize_t
 733generic_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 */
 762int
 763generic_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 */
 779int
 780generic_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
 791EXPORT_SYMBOL(generic_getxattr);
 792EXPORT_SYMBOL(generic_listxattr);
 793EXPORT_SYMBOL(generic_setxattr);
 794EXPORT_SYMBOL(generic_removexattr);
 795
 796/*
 797 * Allocate new xattr and copy in the value; but leave the name to callers.
 798 */
 799struct 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 */
 821int 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
 845static 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        }
 886out:
 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 */
 910int 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 */
 921int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
 922{
 923        return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
 924}
 925
 926static 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 */
 934ssize_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 */
 968void 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}
 975
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.