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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 #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         unsigned int lookup_flags = LOOKUP_FOLLOW;
374 retry:
375         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
376         if (error)
377                 return error;
378         error = mnt_want_write(path.mnt);
379         if (!error) {
380                 error = setxattr(path.dentry, name, value, size, flags);
381                 mnt_drop_write(path.mnt);
382         }
383         path_put(&path);
384         if (retry_estale(error, lookup_flags)) {
385                 lookup_flags |= LOOKUP_REVAL;
386                 goto retry;
387         }
388         return error;
389 }
390 
391 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
392                 const char __user *, name, const void __user *, value,
393                 size_t, size, int, flags)
394 {
395         struct path path;
396         int error;
397         unsigned int lookup_flags = 0;
398 retry:
399         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
400         if (error)
401                 return error;
402         error = mnt_want_write(path.mnt);
403         if (!error) {
404                 error = setxattr(path.dentry, name, value, size, flags);
405                 mnt_drop_write(path.mnt);
406         }
407         path_put(&path);
408         if (retry_estale(error, lookup_flags)) {
409                 lookup_flags |= LOOKUP_REVAL;
410                 goto retry;
411         }
412         return error;
413 }
414 
415 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
416                 const void __user *,value, size_t, size, int, flags)
417 {
418         struct fd f = fdget(fd);
419         struct dentry *dentry;
420         int error = -EBADF;
421 
422         if (!f.file)
423                 return error;
424         dentry = f.file->f_path.dentry;
425         audit_inode(NULL, dentry, 0);
426         error = mnt_want_write_file(f.file);
427         if (!error) {
428                 error = setxattr(dentry, name, value, size, flags);
429                 mnt_drop_write_file(f.file);
430         }
431         fdput(f);
432         return error;
433 }
434 
435 /*
436  * Extended attribute GET operations
437  */
438 static ssize_t
439 getxattr(struct dentry *d, const char __user *name, void __user *value,
440          size_t size)
441 {
442         ssize_t error;
443         void *kvalue = NULL;
444         void *vvalue = NULL;
445         char kname[XATTR_NAME_MAX + 1];
446 
447         error = strncpy_from_user(kname, name, sizeof(kname));
448         if (error == 0 || error == sizeof(kname))
449                 error = -ERANGE;
450         if (error < 0)
451                 return error;
452 
453         if (size) {
454                 if (size > XATTR_SIZE_MAX)
455                         size = XATTR_SIZE_MAX;
456                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
457                 if (!kvalue) {
458                         vvalue = vmalloc(size);
459                         if (!vvalue)
460                                 return -ENOMEM;
461                         kvalue = vvalue;
462                 }
463         }
464 
465         error = vfs_getxattr(d, kname, kvalue, size);
466         if (error > 0) {
467                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
468                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
469                         posix_acl_fix_xattr_to_user(kvalue, size);
470                 if (size && copy_to_user(value, kvalue, error))
471                         error = -EFAULT;
472         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
473                 /* The file system tried to returned a value bigger
474                    than XATTR_SIZE_MAX bytes. Not possible. */
475                 error = -E2BIG;
476         }
477         if (vvalue)
478                 vfree(vvalue);
479         else
480                 kfree(kvalue);
481         return error;
482 }
483 
484 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
485                 const char __user *, name, void __user *, value, size_t, size)
486 {
487         struct path path;
488         ssize_t error;
489         unsigned int lookup_flags = LOOKUP_FOLLOW;
490 retry:
491         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
492         if (error)
493                 return error;
494         error = getxattr(path.dentry, name, value, size);
495         path_put(&path);
496         if (retry_estale(error, lookup_flags)) {
497                 lookup_flags |= LOOKUP_REVAL;
498                 goto retry;
499         }
500         return error;
501 }
502 
503 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
504                 const char __user *, name, void __user *, value, size_t, size)
505 {
506         struct path path;
507         ssize_t error;
508         unsigned int lookup_flags = 0;
509 retry:
510         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
511         if (error)
512                 return error;
513         error = getxattr(path.dentry, name, value, size);
514         path_put(&path);
515         if (retry_estale(error, lookup_flags)) {
516                 lookup_flags |= LOOKUP_REVAL;
517                 goto retry;
518         }
519         return error;
520 }
521 
522 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
523                 void __user *, value, size_t, size)
524 {
525         struct fd f = fdget(fd);
526         ssize_t error = -EBADF;
527 
528         if (!f.file)
529                 return error;
530         audit_inode(NULL, f.file->f_path.dentry, 0);
531         error = getxattr(f.file->f_path.dentry, name, value, size);
532         fdput(f);
533         return error;
534 }
535 
536 /*
537  * Extended attribute LIST operations
538  */
539 static ssize_t
540 listxattr(struct dentry *d, char __user *list, size_t size)
541 {
542         ssize_t error;
543         char *klist = NULL;
544         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
545 
546         if (size) {
547                 if (size > XATTR_LIST_MAX)
548                         size = XATTR_LIST_MAX;
549                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
550                 if (!klist) {
551                         vlist = vmalloc(size);
552                         if (!vlist)
553                                 return -ENOMEM;
554                         klist = vlist;
555                 }
556         }
557 
558         error = vfs_listxattr(d, klist, size);
559         if (error > 0) {
560                 if (size && copy_to_user(list, klist, error))
561                         error = -EFAULT;
562         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
563                 /* The file system tried to returned a list bigger
564                    than XATTR_LIST_MAX bytes. Not possible. */
565                 error = -E2BIG;
566         }
567         if (vlist)
568                 vfree(vlist);
569         else
570                 kfree(klist);
571         return error;
572 }
573 
574 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
575                 size_t, size)
576 {
577         struct path path;
578         ssize_t error;
579         unsigned int lookup_flags = LOOKUP_FOLLOW;
580 retry:
581         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
582         if (error)
583                 return error;
584         error = listxattr(path.dentry, list, size);
585         path_put(&path);
586         if (retry_estale(error, lookup_flags)) {
587                 lookup_flags |= LOOKUP_REVAL;
588                 goto retry;
589         }
590         return error;
591 }
592 
593 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
594                 size_t, size)
595 {
596         struct path path;
597         ssize_t error;
598         unsigned int lookup_flags = 0;
599 retry:
600         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
601         if (error)
602                 return error;
603         error = listxattr(path.dentry, list, size);
604         path_put(&path);
605         if (retry_estale(error, lookup_flags)) {
606                 lookup_flags |= LOOKUP_REVAL;
607                 goto retry;
608         }
609         return error;
610 }
611 
612 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
613 {
614         struct fd f = fdget(fd);
615         ssize_t error = -EBADF;
616 
617         if (!f.file)
618                 return error;
619         audit_inode(NULL, f.file->f_path.dentry, 0);
620         error = listxattr(f.file->f_path.dentry, list, size);
621         fdput(f);
622         return error;
623 }
624 
625 /*
626  * Extended attribute REMOVE operations
627  */
628 static long
629 removexattr(struct dentry *d, const char __user *name)
630 {
631         int error;
632         char kname[XATTR_NAME_MAX + 1];
633 
634         error = strncpy_from_user(kname, name, sizeof(kname));
635         if (error == 0 || error == sizeof(kname))
636                 error = -ERANGE;
637         if (error < 0)
638                 return error;
639 
640         return vfs_removexattr(d, kname);
641 }
642 
643 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
644                 const char __user *, name)
645 {
646         struct path path;
647         int error;
648         unsigned int lookup_flags = LOOKUP_FOLLOW;
649 retry:
650         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
651         if (error)
652                 return error;
653         error = mnt_want_write(path.mnt);
654         if (!error) {
655                 error = removexattr(path.dentry, name);
656                 mnt_drop_write(path.mnt);
657         }
658         path_put(&path);
659         if (retry_estale(error, lookup_flags)) {
660                 lookup_flags |= LOOKUP_REVAL;
661                 goto retry;
662         }
663         return error;
664 }
665 
666 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
667                 const char __user *, name)
668 {
669         struct path path;
670         int error;
671         unsigned int lookup_flags = 0;
672 retry:
673         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
674         if (error)
675                 return error;
676         error = mnt_want_write(path.mnt);
677         if (!error) {
678                 error = removexattr(path.dentry, name);
679                 mnt_drop_write(path.mnt);
680         }
681         path_put(&path);
682         if (retry_estale(error, lookup_flags)) {
683                 lookup_flags |= LOOKUP_REVAL;
684                 goto retry;
685         }
686         return error;
687 }
688 
689 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
690 {
691         struct fd f = fdget(fd);
692         struct dentry *dentry;
693         int error = -EBADF;
694 
695         if (!f.file)
696                 return error;
697         dentry = f.file->f_path.dentry;
698         audit_inode(NULL, dentry, 0);
699         error = mnt_want_write_file(f.file);
700         if (!error) {
701                 error = removexattr(dentry, name);
702                 mnt_drop_write_file(f.file);
703         }
704         fdput(f);
705         return error;
706 }
707 
708 
709 static const char *
710 strcmp_prefix(const char *a, const char *a_prefix)
711 {
712         while (*a_prefix && *a == *a_prefix) {
713                 a++;
714                 a_prefix++;
715         }
716         return *a_prefix ? NULL : a;
717 }
718 
719 /*
720  * In order to implement different sets of xattr operations for each xattr
721  * prefix with the generic xattr API, a filesystem should create a
722  * null-terminated array of struct xattr_handler (one for each prefix) and
723  * hang a pointer to it off of the s_xattr field of the superblock.
724  *
725  * The generic_fooxattr() functions will use this list to dispatch xattr
726  * operations to the correct xattr_handler.
727  */
728 #define for_each_xattr_handler(handlers, handler)               \
729                 for ((handler) = *(handlers)++;                 \
730                         (handler) != NULL;                      \
731                         (handler) = *(handlers)++)
732 
733 /*
734  * Find the xattr_handler with the matching prefix.
735  */
736 static const struct xattr_handler *
737 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
738 {
739         const struct xattr_handler *handler;
740 
741         if (!*name)
742                 return NULL;
743 
744         for_each_xattr_handler(handlers, handler) {
745                 const char *n = strcmp_prefix(*name, handler->prefix);
746                 if (n) {
747                         *name = n;
748                         break;
749                 }
750         }
751         return handler;
752 }
753 
754 /*
755  * Find the handler for the prefix and dispatch its get() operation.
756  */
757 ssize_t
758 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
759 {
760         const struct xattr_handler *handler;
761 
762         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
763         if (!handler)
764                 return -EOPNOTSUPP;
765         return handler->get(dentry, name, buffer, size, handler->flags);
766 }
767 
768 /*
769  * Combine the results of the list() operation from every xattr_handler in the
770  * list.
771  */
772 ssize_t
773 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
774 {
775         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
776         unsigned int size = 0;
777 
778         if (!buffer) {
779                 for_each_xattr_handler(handlers, handler) {
780                         size += handler->list(dentry, NULL, 0, NULL, 0,
781                                               handler->flags);
782                 }
783         } else {
784                 char *buf = buffer;
785 
786                 for_each_xattr_handler(handlers, handler) {
787                         size = handler->list(dentry, buf, buffer_size,
788                                              NULL, 0, handler->flags);
789                         if (size > buffer_size)
790                                 return -ERANGE;
791                         buf += size;
792                         buffer_size -= size;
793                 }
794                 size = buf - buffer;
795         }
796         return size;
797 }
798 
799 /*
800  * Find the handler for the prefix and dispatch its set() operation.
801  */
802 int
803 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
804 {
805         const struct xattr_handler *handler;
806 
807         if (size == 0)
808                 value = "";  /* empty EA, do not remove */
809         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
810         if (!handler)
811                 return -EOPNOTSUPP;
812         return handler->set(dentry, name, value, size, flags, handler->flags);
813 }
814 
815 /*
816  * Find the handler for the prefix and dispatch its set() operation to remove
817  * any associated extended attribute.
818  */
819 int
820 generic_removexattr(struct dentry *dentry, const char *name)
821 {
822         const struct xattr_handler *handler;
823 
824         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
825         if (!handler)
826                 return -EOPNOTSUPP;
827         return handler->set(dentry, name, NULL, 0,
828                             XATTR_REPLACE, handler->flags);
829 }
830 
831 EXPORT_SYMBOL(generic_getxattr);
832 EXPORT_SYMBOL(generic_listxattr);
833 EXPORT_SYMBOL(generic_setxattr);
834 EXPORT_SYMBOL(generic_removexattr);
835 
836 /*
837  * Allocate new xattr and copy in the value; but leave the name to callers.
838  */
839 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
840 {
841         struct simple_xattr *new_xattr;
842         size_t len;
843 
844         /* wrap around? */
845         len = sizeof(*new_xattr) + size;
846         if (len <= sizeof(*new_xattr))
847                 return NULL;
848 
849         new_xattr = kmalloc(len, GFP_KERNEL);
850         if (!new_xattr)
851                 return NULL;
852 
853         new_xattr->size = size;
854         memcpy(new_xattr->value, value, size);
855         return new_xattr;
856 }
857 
858 /*
859  * xattr GET operation for in-memory/pseudo filesystems
860  */
861 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
862                      void *buffer, size_t size)
863 {
864         struct simple_xattr *xattr;
865         int ret = -ENODATA;
866 
867         spin_lock(&xattrs->lock);
868         list_for_each_entry(xattr, &xattrs->head, list) {
869                 if (strcmp(name, xattr->name))
870                         continue;
871 
872                 ret = xattr->size;
873                 if (buffer) {
874                         if (size < xattr->size)
875                                 ret = -ERANGE;
876                         else
877                                 memcpy(buffer, xattr->value, xattr->size);
878                 }
879                 break;
880         }
881         spin_unlock(&xattrs->lock);
882         return ret;
883 }
884 
885 static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
886                               const void *value, size_t size, int flags)
887 {
888         struct simple_xattr *xattr;
889         struct simple_xattr *new_xattr = NULL;
890         int err = 0;
891 
892         /* value == NULL means remove */
893         if (value) {
894                 new_xattr = simple_xattr_alloc(value, size);
895                 if (!new_xattr)
896                         return -ENOMEM;
897 
898                 new_xattr->name = kstrdup(name, GFP_KERNEL);
899                 if (!new_xattr->name) {
900                         kfree(new_xattr);
901                         return -ENOMEM;
902                 }
903         }
904 
905         spin_lock(&xattrs->lock);
906         list_for_each_entry(xattr, &xattrs->head, list) {
907                 if (!strcmp(name, xattr->name)) {
908                         if (flags & XATTR_CREATE) {
909                                 xattr = new_xattr;
910                                 err = -EEXIST;
911                         } else if (new_xattr) {
912                                 list_replace(&xattr->list, &new_xattr->list);
913                         } else {
914                                 list_del(&xattr->list);
915                         }
916                         goto out;
917                 }
918         }
919         if (flags & XATTR_REPLACE) {
920                 xattr = new_xattr;
921                 err = -ENODATA;
922         } else {
923                 list_add(&new_xattr->list, &xattrs->head);
924                 xattr = NULL;
925         }
926 out:
927         spin_unlock(&xattrs->lock);
928         if (xattr) {
929                 kfree(xattr->name);
930                 kfree(xattr);
931         }
932         return err;
933 
934 }
935 
936 /**
937  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
938  * @xattrs: target simple_xattr list
939  * @name: name of the new extended attribute
940  * @value: value of the new xattr. If %NULL, will remove the attribute
941  * @size: size of the new xattr
942  * @flags: %XATTR_{CREATE|REPLACE}
943  *
944  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
945  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
946  * otherwise, fails with -ENODATA.
947  *
948  * Returns 0 on success, -errno on failure.
949  */
950 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
951                      const void *value, size_t size, int flags)
952 {
953         if (size == 0)
954                 value = ""; /* empty EA, do not remove */
955         return __simple_xattr_set(xattrs, name, value, size, flags);
956 }
957 
958 /*
959  * xattr REMOVE operation for in-memory/pseudo filesystems
960  */
961 int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
962 {
963         return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
964 }
965 
966 static bool xattr_is_trusted(const char *name)
967 {
968         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
969 }
970 
971 /*
972  * xattr LIST operation for in-memory/pseudo filesystems
973  */
974 ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
975                           size_t size)
976 {
977         bool trusted = capable(CAP_SYS_ADMIN);
978         struct simple_xattr *xattr;
979         size_t used = 0;
980 
981         spin_lock(&xattrs->lock);
982         list_for_each_entry(xattr, &xattrs->head, list) {
983                 size_t len;
984 
985                 /* skip "trusted." attributes for unprivileged callers */
986                 if (!trusted && xattr_is_trusted(xattr->name))
987                         continue;
988 
989                 len = strlen(xattr->name) + 1;
990                 used += len;
991                 if (buffer) {
992                         if (size < used) {
993                                 used = -ERANGE;
994                                 break;
995                         }
996                         memcpy(buffer, xattr->name, len);
997                         buffer += len;
998                 }
999         }
1000         spin_unlock(&xattrs->lock);
1001 
1002         return used;
1003 }
1004 
1005 /*
1006  * Adds an extended attribute to the list
1007  */
1008 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1009                            struct simple_xattr *new_xattr)
1010 {
1011         spin_lock(&xattrs->lock);
1012         list_add(&new_xattr->list, &xattrs->head);
1013         spin_unlock(&xattrs->lock);
1014 }
1015 

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