Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
/*
  File: fs/xattr.c

  Extended attribute handling.

  Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
  Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
  Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
 */
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/xattr.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/evm.h>
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/fsnotify.h>
#include <linux/audit.h>
#include <linux/vmalloc.h>
#include <linux/posix_acl_xattr.h>

#include <linux/uaccess.h>

static const char *
strcmp_prefix(const char *a, const char *a_prefix)
{
	while (*a_prefix && *a == *a_prefix) {
		a++;
		a_prefix++;
	}
	return *a_prefix ? NULL : a;
}

/*
 * In order to implement different sets of xattr operations for each xattr
 * prefix, a filesystem should create a null-terminated array of struct
 * xattr_handler (one for each prefix) and hang a pointer to it off of the
 * s_xattr field of the superblock.
 */
#define for_each_xattr_handler(handlers, handler)		\
	if (handlers)						\
		for ((handler) = *(handlers)++;			\
			(handler) != NULL;			\
			(handler) = *(handlers)++)

/*
 * Find the xattr_handler with the matching prefix.
 */
static const struct xattr_handler *
xattr_resolve_name(struct inode *inode, const char **name)
{
	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
	const struct xattr_handler *handler;

	if (!(inode->i_opflags & IOP_XATTR)) {
		if (unlikely(is_bad_inode(inode)))
			return ERR_PTR(-EIO);
		return ERR_PTR(-EOPNOTSUPP);
	}
	for_each_xattr_handler(handlers, handler) {
		const char *n;

		n = strcmp_prefix(*name, xattr_prefix(handler));
		if (n) {
			if (!handler->prefix ^ !*n) {
				if (*n)
					continue;
				return ERR_PTR(-EINVAL);
			}
			*name = n;
			return handler;
		}
	}
	return ERR_PTR(-EOPNOTSUPP);
}

/*
 * Check permissions for extended attribute access.  This is a bit complicated
 * because different namespaces have very different rules.
 */
static int
xattr_permission(struct inode *inode, const char *name, int mask)
{
	/*
	 * We can never set or remove an extended attribute on a read-only
	 * filesystem  or on an immutable / append-only inode.
	 */
	if (mask & MAY_WRITE) {
		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
			return -EPERM;
		/*
		 * Updating an xattr will likely cause i_uid and i_gid
		 * to be writen back improperly if their true value is
		 * unknown to the vfs.
		 */
		if (HAS_UNMAPPED_ID(inode))
			return -EPERM;
	}

	/*
	 * No restriction for security.* and system.* from the VFS.  Decision
	 * on these is left to the underlying filesystem / security module.
	 */
	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
		return 0;

	/*
	 * The trusted.* namespace can only be accessed by privileged users.
	 */
	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
		if (!capable(CAP_SYS_ADMIN))
			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
		return 0;
	}

	/*
	 * In the user.* namespace, only regular files and directories can have
	 * extended attributes. For sticky directories, only the owner and
	 * privileged users can write attributes.
	 */
	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
		    (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
			return -EPERM;
	}

	return inode_permission(inode, mask);
}

int
__vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
	       const void *value, size_t size, int flags)
{
	const struct xattr_handler *handler;

	handler = xattr_resolve_name(inode, &name);
	if (IS_ERR(handler))
		return PTR_ERR(handler);
	if (!handler->set)
		return -EOPNOTSUPP;
	if (size == 0)
		value = "";  /* empty EA, do not remove */
	return handler->set(handler, dentry, inode, name, value, size, flags);
}
EXPORT_SYMBOL(__vfs_setxattr);

/**
 *  __vfs_setxattr_noperm - perform setxattr operation without performing
 *  permission checks.
 *
 *  @dentry - object to perform setxattr on
 *  @name - xattr name to set
 *  @value - value to set @name to
 *  @size - size of @value
 *  @flags - flags to pass into filesystem operations
 *
 *  returns the result of the internal setxattr or setsecurity operations.
 *
 *  This function requires the caller to lock the inode's i_mutex before it
 *  is executed. It also assumes that the caller will make the appropriate
 *  permission checks.
 */
int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
		const void *value, size_t size, int flags)
{
	struct inode *inode = dentry->d_inode;
	int error = -EAGAIN;
	int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
				   XATTR_SECURITY_PREFIX_LEN);

	if (issec)
		inode->i_flags &= ~S_NOSEC;
	if (inode->i_opflags & IOP_XATTR) {
		error = __vfs_setxattr(dentry, inode, name, value, size, flags);
		if (!error) {
			fsnotify_xattr(dentry);
			security_inode_post_setxattr(dentry, name, value,
						     size, flags);
		}
	} else {
		if (unlikely(is_bad_inode(inode)))
			return -EIO;
	}
	if (error == -EAGAIN) {
		error = -EOPNOTSUPP;

		if (issec) {
			const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;

			error = security_inode_setsecurity(inode, suffix, value,
							   size, flags);
			if (!error)
				fsnotify_xattr(dentry);
		}
	}

	return error;
}


int
vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
		size_t size, int flags)
{
	struct inode *inode = dentry->d_inode;
	int error;

	error = xattr_permission(inode, name, MAY_WRITE);
	if (error)
		return error;

	inode_lock(inode);
	error = security_inode_setxattr(dentry, name, value, size, flags);
	if (error)
		goto out;

	error = __vfs_setxattr_noperm(dentry, name, value, size, flags);

out:
	inode_unlock(inode);
	return error;
}
EXPORT_SYMBOL_GPL(vfs_setxattr);

ssize_t
xattr_getsecurity(struct inode *inode, const char *name, void *value,
			size_t size)
{
	void *buffer = NULL;
	ssize_t len;

	if (!value || !size) {
		len = security_inode_getsecurity(inode, name, &buffer, false);
		goto out_noalloc;
	}

	len = security_inode_getsecurity(inode, name, &buffer, true);
	if (len < 0)
		return len;
	if (size < len) {
		len = -ERANGE;
		goto out;
	}
	memcpy(value, buffer, len);
out:
	kfree(buffer);
out_noalloc:
	return len;
}
EXPORT_SYMBOL_GPL(xattr_getsecurity);

/*
 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 *
 * Allocate memory, if not already allocated, or re-allocate correct size,
 * before retrieving the extended attribute.
 *
 * Returns the result of alloc, if failed, or the getxattr operation.
 */
ssize_t
vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
		   size_t xattr_size, gfp_t flags)
{
	const struct xattr_handler *handler;
	struct inode *inode = dentry->d_inode;
	char *value = *xattr_value;
	int error;

	error = xattr_permission(inode, name, MAY_READ);
	if (error)
		return error;

	handler = xattr_resolve_name(inode, &name);
	if (IS_ERR(handler))
		return PTR_ERR(handler);
	if (!handler->get)
		return -EOPNOTSUPP;
	error = handler->get(handler, dentry, inode, name, NULL, 0);
	if (error < 0)
		return error;

	if (!value || (error > xattr_size)) {
		value = krealloc(*xattr_value, error + 1, flags);
		if (!value)
			return -ENOMEM;
		memset(value, 0, error + 1);
	}

	error = handler->get(handler, dentry, inode, name, value, error);
	*xattr_value = value;
	return error;
}

ssize_t
__vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
	       void *value, size_t size)
{
	const struct xattr_handler *handler;

	handler = xattr_resolve_name(inode, &name);
	if (IS_ERR(handler))
		return PTR_ERR(handler);
	if (!handler->get)
		return -EOPNOTSUPP;
	return handler->get(handler, dentry, inode, name, value, size);
}
EXPORT_SYMBOL(__vfs_getxattr);

ssize_t
vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
{
	struct inode *inode = dentry->d_inode;
	int error;

	error = xattr_permission(inode, name, MAY_READ);
	if (error)
		return error;

	error = security_inode_getxattr(dentry, name);
	if (error)
		return error;

	if (!strncmp(name, XATTR_SECURITY_PREFIX,
				XATTR_SECURITY_PREFIX_LEN)) {
		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
		int ret = xattr_getsecurity(inode, suffix, value, size);
		/*
		 * Only overwrite the return value if a security module
		 * is actually active.
		 */
		if (ret == -EOPNOTSUPP)
			goto nolsm;
		return ret;
	}
nolsm:
	return __vfs_getxattr(dentry, inode, name, value, size);
}
EXPORT_SYMBOL_GPL(vfs_getxattr);

ssize_t
vfs_listxattr(struct dentry *dentry, char *list, size_t size)
{
	struct inode *inode = d_inode(dentry);
	ssize_t error;

	error = security_inode_listxattr(dentry);
	if (error)
		return error;
	if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
		error = -EOPNOTSUPP;
		error = inode->i_op->listxattr(dentry, list, size);
	} else {
		error = security_inode_listsecurity(inode, list, size);
		if (size && error > size)
			error = -ERANGE;
	}
	return error;
}
EXPORT_SYMBOL_GPL(vfs_listxattr);

int
__vfs_removexattr(struct dentry *dentry, const char *name)
{
	struct inode *inode = d_inode(dentry);
	const struct xattr_handler *handler;

	handler = xattr_resolve_name(inode, &name);
	if (IS_ERR(handler))
		return PTR_ERR(handler);
	if (!handler->set)
		return -EOPNOTSUPP;
	return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
}
EXPORT_SYMBOL(__vfs_removexattr);

int
vfs_removexattr(struct dentry *dentry, const char *name)
{
	struct inode *inode = dentry->d_inode;
	int error;

	error = xattr_permission(inode, name, MAY_WRITE);
	if (error)
		return error;

	inode_lock(inode);
	error = security_inode_removexattr(dentry, name);
	if (error)
		goto out;

	error = __vfs_removexattr(dentry, name);

	if (!error) {
		fsnotify_xattr(dentry);
		evm_inode_post_removexattr(dentry, name);
	}

out:
	inode_unlock(inode);
	return error;
}
EXPORT_SYMBOL_GPL(vfs_removexattr);


/*
 * Extended attribute SET operations
 */
static long
setxattr(struct dentry *d, const char __user *name, const void __user *value,
	 size_t size, int flags)
{
	int error;
	void *kvalue = NULL;
	char kname[XATTR_NAME_MAX + 1];

	if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
		return -EINVAL;

	error = strncpy_from_user(kname, name, sizeof(kname));
	if (error == 0 || error == sizeof(kname))
		error = -ERANGE;
	if (error < 0)
		return error;

	if (size) {
		if (size > XATTR_SIZE_MAX)
			return -E2BIG;
		kvalue = kvmalloc(size, GFP_KERNEL);
		if (!kvalue)
			return -ENOMEM;
		if (copy_from_user(kvalue, value, size)) {
			error = -EFAULT;
			goto out;
		}
		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
			posix_acl_fix_xattr_from_user(kvalue, size);
	}

	error = vfs_setxattr(d, kname, kvalue, size, flags);
out:
	kvfree(kvalue);

	return error;
}

static int path_setxattr(const char __user *pathname,
			 const char __user *name, const void __user *value,
			 size_t size, int flags, unsigned int lookup_flags)
{
	struct path path;
	int error;
retry:
	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
	if (error)
		return error;
	error = mnt_want_write(path.mnt);
	if (!error) {
		error = setxattr(path.dentry, name, value, size, flags);
		mnt_drop_write(path.mnt);
	}
	path_put(&path);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}

SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
		const char __user *, name, const void __user *, value,
		size_t, size, int, flags)
{
	return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
}

SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
		const char __user *, name, const void __user *, value,
		size_t, size, int, flags)
{
	return path_setxattr(pathname, name, value, size, flags, 0);
}

SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
		const void __user *,value, size_t, size, int, flags)
{
	struct fd f = fdget(fd);
	int error = -EBADF;

	if (!f.file)
		return error;
	audit_file(f.file);
	error = mnt_want_write_file(f.file);
	if (!error) {
		error = setxattr(f.file->f_path.dentry, name, value, size, flags);
		mnt_drop_write_file(f.file);
	}
	fdput(f);
	return error;
}

/*
 * Extended attribute GET operations
 */
static ssize_t
getxattr(struct dentry *d, const char __user *name, void __user *value,
	 size_t size)
{
	ssize_t error;
	void *kvalue = NULL;
	char kname[XATTR_NAME_MAX + 1];

	error = strncpy_from_user(kname, name, sizeof(kname));
	if (error == 0 || error == sizeof(kname))
		error = -ERANGE;
	if (error < 0)
		return error;

	if (size) {
		if (size > XATTR_SIZE_MAX)
			size = XATTR_SIZE_MAX;
		kvalue = kvzalloc(size, GFP_KERNEL);
		if (!kvalue)
			return -ENOMEM;
	}

	error = vfs_getxattr(d, kname, kvalue, size);
	if (error > 0) {
		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
			posix_acl_fix_xattr_to_user(kvalue, size);
		if (size && copy_to_user(value, kvalue, error))
			error = -EFAULT;
	} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
		/* The file system tried to returned a value bigger
		   than XATTR_SIZE_MAX bytes. Not possible. */
		error = -E2BIG;
	}

	kvfree(kvalue);

	return error;
}

static ssize_t path_getxattr(const char __user *pathname,
			     const char __user *name, void __user *value,
			     size_t size, unsigned int lookup_flags)
{
	struct path path;
	ssize_t error;
retry:
	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
	if (error)
		return error;
	error = getxattr(path.dentry, name, value, size);
	path_put(&path);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}

SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
		const char __user *, name, void __user *, value, size_t, size)
{
	return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
}

SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
		const char __user *, name, void __user *, value, size_t, size)
{
	return path_getxattr(pathname, name, value, size, 0);
}

SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
		void __user *, value, size_t, size)
{
	struct fd f = fdget(fd);
	ssize_t error = -EBADF;

	if (!f.file)
		return error;
	audit_file(f.file);
	error = getxattr(f.file->f_path.dentry, name, value, size);
	fdput(f);
	return error;
}

/*
 * Extended attribute LIST operations
 */
static ssize_t
listxattr(struct dentry *d, char __user *list, size_t size)
{
	ssize_t error;
	char *klist = NULL;

	if (size) {
		if (size > XATTR_LIST_MAX)
			size = XATTR_LIST_MAX;
		klist = kvmalloc(size, GFP_KERNEL);
		if (!klist)
			return -ENOMEM;
	}

	error = vfs_listxattr(d, klist, size);
	if (error > 0) {
		if (size && copy_to_user(list, klist, error))
			error = -EFAULT;
	} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
		/* The file system tried to returned a list bigger
		   than XATTR_LIST_MAX bytes. Not possible. */
		error = -E2BIG;
	}

	kvfree(klist);

	return error;
}

static ssize_t path_listxattr(const char __user *pathname, char __user *list,
			      size_t size, unsigned int lookup_flags)
{
	struct path path;
	ssize_t error;
retry:
	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
	if (error)
		return error;
	error = listxattr(path.dentry, list, size);
	path_put(&path);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}

SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
		size_t, size)
{
	return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
}

SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
		size_t, size)
{
	return path_listxattr(pathname, list, size, 0);
}

SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
{
	struct fd f = fdget(fd);
	ssize_t error = -EBADF;

	if (!f.file)
		return error;
	audit_file(f.file);
	error = listxattr(f.file->f_path.dentry, list, size);
	fdput(f);
	return error;
}

/*
 * Extended attribute REMOVE operations
 */
static long
removexattr(struct dentry *d, const char __user *name)
{
	int error;
	char kname[XATTR_NAME_MAX + 1];

	error = strncpy_from_user(kname, name, sizeof(kname));
	if (error == 0 || error == sizeof(kname))
		error = -ERANGE;
	if (error < 0)
		return error;

	return vfs_removexattr(d, kname);
}

static int path_removexattr(const char __user *pathname,
			    const char __user *name, unsigned int lookup_flags)
{
	struct path path;
	int error;
retry:
	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
	if (error)
		return error;
	error = mnt_want_write(path.mnt);
	if (!error) {
		error = removexattr(path.dentry, name);
		mnt_drop_write(path.mnt);
	}
	path_put(&path);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}

SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
		const char __user *, name)
{
	return path_removexattr(pathname, name, LOOKUP_FOLLOW);
}

SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
		const char __user *, name)
{
	return path_removexattr(pathname, name, 0);
}

SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
{
	struct fd f = fdget(fd);
	int error = -EBADF;

	if (!f.file)
		return error;
	audit_file(f.file);
	error = mnt_want_write_file(f.file);
	if (!error) {
		error = removexattr(f.file->f_path.dentry, name);
		mnt_drop_write_file(f.file);
	}
	fdput(f);
	return error;
}

/*
 * Combine the results of the list() operation from every xattr_handler in the
 * list.
 */
ssize_t
generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
{
	const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
	unsigned int size = 0;

	if (!buffer) {
		for_each_xattr_handler(handlers, handler) {
			if (!handler->name ||
			    (handler->list && !handler->list(dentry)))
				continue;
			size += strlen(handler->name) + 1;
		}
	} else {
		char *buf = buffer;
		size_t len;

		for_each_xattr_handler(handlers, handler) {
			if (!handler->name ||
			    (handler->list && !handler->list(dentry)))
				continue;
			len = strlen(handler->name);
			if (len + 1 > buffer_size)
				return -ERANGE;
			memcpy(buf, handler->name, len + 1);
			buf += len + 1;
			buffer_size -= len + 1;
		}
		size = buf - buffer;
	}
	return size;
}
EXPORT_SYMBOL(generic_listxattr);

/**
 * xattr_full_name  -  Compute full attribute name from suffix
 *
 * @handler:	handler of the xattr_handler operation
 * @name:	name passed to the xattr_handler operation
 *
 * The get and set xattr handler operations are called with the remainder of
 * the attribute name after skipping the handler's prefix: for example, "foo"
 * is passed to the get operation of a handler with prefix "user." to get
 * attribute "user.foo".  The full name is still "there" in the name though.
 *
 * Note: the list xattr handler operation when called from the vfs is passed a
 * NULL name; some file systems use this operation internally, with varying
 * semantics.
 */
const char *xattr_full_name(const struct xattr_handler *handler,
			    const char *name)
{
	size_t prefix_len = strlen(xattr_prefix(handler));

	return name - prefix_len;
}
EXPORT_SYMBOL(xattr_full_name);

/*
 * Allocate new xattr and copy in the value; but leave the name to callers.
 */
struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
{
	struct simple_xattr *new_xattr;
	size_t len;

	/* wrap around? */
	len = sizeof(*new_xattr) + size;
	if (len < sizeof(*new_xattr))
		return NULL;

	new_xattr = kmalloc(len, GFP_KERNEL);
	if (!new_xattr)
		return NULL;

	new_xattr->size = size;
	memcpy(new_xattr->value, value, size);
	return new_xattr;
}

/*
 * xattr GET operation for in-memory/pseudo filesystems
 */
int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
		     void *buffer, size_t size)
{
	struct simple_xattr *xattr;
	int ret = -ENODATA;

	spin_lock(&xattrs->lock);
	list_for_each_entry(xattr, &xattrs->head, list) {
		if (strcmp(name, xattr->name))
			continue;

		ret = xattr->size;
		if (buffer) {
			if (size < xattr->size)
				ret = -ERANGE;
			else
				memcpy(buffer, xattr->value, xattr->size);
		}
		break;
	}
	spin_unlock(&xattrs->lock);
	return ret;
}

/**
 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 * @xattrs: target simple_xattr list
 * @name: name of the extended attribute
 * @value: value of the xattr. If %NULL, will remove the attribute.
 * @size: size of the new xattr
 * @flags: %XATTR_{CREATE|REPLACE}
 *
 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 * otherwise, fails with -ENODATA.
 *
 * Returns 0 on success, -errno on failure.
 */
int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
		     const void *value, size_t size, int flags)
{
	struct simple_xattr *xattr;
	struct simple_xattr *new_xattr = NULL;
	int err = 0;

	/* value == NULL means remove */
	if (value) {
		new_xattr = simple_xattr_alloc(value, size);
		if (!new_xattr)
			return -ENOMEM;

		new_xattr->name = kstrdup(name, GFP_KERNEL);
		if (!new_xattr->name) {
			kfree(new_xattr);
			return -ENOMEM;
		}
	}

	spin_lock(&xattrs->lock);
	list_for_each_entry(xattr, &xattrs->head, list) {
		if (!strcmp(name, xattr->name)) {
			if (flags & XATTR_CREATE) {
				xattr = new_xattr;
				err = -EEXIST;
			} else if (new_xattr) {
				list_replace(&xattr->list, &new_xattr->list);
			} else {
				list_del(&xattr->list);
			}
			goto out;
		}
	}
	if (flags & XATTR_REPLACE) {
		xattr = new_xattr;
		err = -ENODATA;
	} else {
		list_add(&new_xattr->list, &xattrs->head);
		xattr = NULL;
	}
out:
	spin_unlock(&xattrs->lock);
	if (xattr) {
		kfree(xattr->name);
		kfree(xattr);
	}
	return err;

}

static bool xattr_is_trusted(const char *name)
{
	return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
}

static int xattr_list_one(char **buffer, ssize_t *remaining_size,
			  const char *name)
{
	size_t len = strlen(name) + 1;
	if (*buffer) {
		if (*remaining_size < len)
			return -ERANGE;
		memcpy(*buffer, name, len);
		*buffer += len;
	}
	*remaining_size -= len;
	return 0;
}

/*
 * xattr LIST operation for in-memory/pseudo filesystems
 */
ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
			  char *buffer, size_t size)
{
	bool trusted = capable(CAP_SYS_ADMIN);
	struct simple_xattr *xattr;
	ssize_t remaining_size = size;
	int err = 0;

#ifdef CONFIG_FS_POSIX_ACL
	if (inode->i_acl) {
		err = xattr_list_one(&buffer, &remaining_size,
				     XATTR_NAME_POSIX_ACL_ACCESS);
		if (err)
			return err;
	}
	if (inode->i_default_acl) {
		err = xattr_list_one(&buffer, &remaining_size,
				     XATTR_NAME_POSIX_ACL_DEFAULT);
		if (err)
			return err;
	}
#endif

	spin_lock(&xattrs->lock);
	list_for_each_entry(xattr, &xattrs->head, list) {
		/* skip "trusted." attributes for unprivileged callers */
		if (!trusted && xattr_is_trusted(xattr->name))
			continue;

		err = xattr_list_one(&buffer, &remaining_size, xattr->name);
		if (err)
			break;
	}
	spin_unlock(&xattrs->lock);

	return err ? err : size - remaining_size;
}

/*
 * Adds an extended attribute to the list
 */
void simple_xattr_list_add(struct simple_xattrs *xattrs,
			   struct simple_xattr *new_xattr)
{
	spin_lock(&xattrs->lock);
	list_add(&new_xattr->list, &xattrs->head);
	spin_unlock(&xattrs->lock);
}