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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                 goto out;
303 
304         error = inode->i_op->removexattr(dentry, name);
305 
306         if (!error) {
307                 fsnotify_xattr(dentry);
308                 evm_inode_post_removexattr(dentry, name);
309         }
310 
311 out:
312         mutex_unlock(&inode->i_mutex);
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 static int path_setxattr(const char __user *pathname,
368                          const char __user *name, const void __user *value,
369                          size_t size, int flags, unsigned int lookup_flags)
370 {
371         struct path path;
372         int error;
373 retry:
374         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &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         if (retry_estale(error, lookup_flags)) {
384                 lookup_flags |= LOOKUP_REVAL;
385                 goto retry;
386         }
387         return error;
388 }
389 
390 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
391                 const char __user *, name, const void __user *, value,
392                 size_t, size, int, flags)
393 {
394         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
395 }
396 
397 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
398                 const char __user *, name, const void __user *, value,
399                 size_t, size, int, flags)
400 {
401         return path_setxattr(pathname, name, value, size, flags, 0);
402 }
403 
404 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
405                 const void __user *,value, size_t, size, int, flags)
406 {
407         struct fd f = fdget(fd);
408         int error = -EBADF;
409 
410         if (!f.file)
411                 return error;
412         audit_file(f.file);
413         error = mnt_want_write_file(f.file);
414         if (!error) {
415                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
416                 mnt_drop_write_file(f.file);
417         }
418         fdput(f);
419         return error;
420 }
421 
422 /*
423  * Extended attribute GET operations
424  */
425 static ssize_t
426 getxattr(struct dentry *d, const char __user *name, void __user *value,
427          size_t size)
428 {
429         ssize_t error;
430         void *kvalue = NULL;
431         void *vvalue = NULL;
432         char kname[XATTR_NAME_MAX + 1];
433 
434         error = strncpy_from_user(kname, name, sizeof(kname));
435         if (error == 0 || error == sizeof(kname))
436                 error = -ERANGE;
437         if (error < 0)
438                 return error;
439 
440         if (size) {
441                 if (size > XATTR_SIZE_MAX)
442                         size = XATTR_SIZE_MAX;
443                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
444                 if (!kvalue) {
445                         vvalue = vmalloc(size);
446                         if (!vvalue)
447                                 return -ENOMEM;
448                         kvalue = vvalue;
449                 }
450         }
451 
452         error = vfs_getxattr(d, kname, kvalue, size);
453         if (error > 0) {
454                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
455                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
456                         posix_acl_fix_xattr_to_user(kvalue, size);
457                 if (size && copy_to_user(value, kvalue, error))
458                         error = -EFAULT;
459         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
460                 /* The file system tried to returned a value bigger
461                    than XATTR_SIZE_MAX bytes. Not possible. */
462                 error = -E2BIG;
463         }
464         if (vvalue)
465                 vfree(vvalue);
466         else
467                 kfree(kvalue);
468         return error;
469 }
470 
471 static ssize_t path_getxattr(const char __user *pathname,
472                              const char __user *name, void __user *value,
473                              size_t size, unsigned int lookup_flags)
474 {
475         struct path path;
476         ssize_t error;
477 retry:
478         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
479         if (error)
480                 return error;
481         error = getxattr(path.dentry, name, value, size);
482         path_put(&path);
483         if (retry_estale(error, lookup_flags)) {
484                 lookup_flags |= LOOKUP_REVAL;
485                 goto retry;
486         }
487         return error;
488 }
489 
490 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
491                 const char __user *, name, void __user *, value, size_t, size)
492 {
493         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
494 }
495 
496 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
497                 const char __user *, name, void __user *, value, size_t, size)
498 {
499         return path_getxattr(pathname, name, value, size, 0);
500 }
501 
502 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
503                 void __user *, value, size_t, size)
504 {
505         struct fd f = fdget(fd);
506         ssize_t error = -EBADF;
507 
508         if (!f.file)
509                 return error;
510         audit_file(f.file);
511         error = getxattr(f.file->f_path.dentry, name, value, size);
512         fdput(f);
513         return error;
514 }
515 
516 /*
517  * Extended attribute LIST operations
518  */
519 static ssize_t
520 listxattr(struct dentry *d, char __user *list, size_t size)
521 {
522         ssize_t error;
523         char *klist = NULL;
524         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
525 
526         if (size) {
527                 if (size > XATTR_LIST_MAX)
528                         size = XATTR_LIST_MAX;
529                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
530                 if (!klist) {
531                         vlist = vmalloc(size);
532                         if (!vlist)
533                                 return -ENOMEM;
534                         klist = vlist;
535                 }
536         }
537 
538         error = vfs_listxattr(d, klist, size);
539         if (error > 0) {
540                 if (size && copy_to_user(list, klist, error))
541                         error = -EFAULT;
542         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
543                 /* The file system tried to returned a list bigger
544                    than XATTR_LIST_MAX bytes. Not possible. */
545                 error = -E2BIG;
546         }
547         if (vlist)
548                 vfree(vlist);
549         else
550                 kfree(klist);
551         return error;
552 }
553 
554 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
555                               size_t size, unsigned int lookup_flags)
556 {
557         struct path path;
558         ssize_t error;
559 retry:
560         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
561         if (error)
562                 return error;
563         error = listxattr(path.dentry, list, size);
564         path_put(&path);
565         if (retry_estale(error, lookup_flags)) {
566                 lookup_flags |= LOOKUP_REVAL;
567                 goto retry;
568         }
569         return error;
570 }
571 
572 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
573                 size_t, size)
574 {
575         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
576 }
577 
578 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
579                 size_t, size)
580 {
581         return path_listxattr(pathname, list, size, 0);
582 }
583 
584 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
585 {
586         struct fd f = fdget(fd);
587         ssize_t error = -EBADF;
588 
589         if (!f.file)
590                 return error;
591         audit_file(f.file);
592         error = listxattr(f.file->f_path.dentry, list, size);
593         fdput(f);
594         return error;
595 }
596 
597 /*
598  * Extended attribute REMOVE operations
599  */
600 static long
601 removexattr(struct dentry *d, const char __user *name)
602 {
603         int error;
604         char kname[XATTR_NAME_MAX + 1];
605 
606         error = strncpy_from_user(kname, name, sizeof(kname));
607         if (error == 0 || error == sizeof(kname))
608                 error = -ERANGE;
609         if (error < 0)
610                 return error;
611 
612         return vfs_removexattr(d, kname);
613 }
614 
615 static int path_removexattr(const char __user *pathname,
616                             const char __user *name, unsigned int lookup_flags)
617 {
618         struct path path;
619         int error;
620 retry:
621         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
622         if (error)
623                 return error;
624         error = mnt_want_write(path.mnt);
625         if (!error) {
626                 error = removexattr(path.dentry, name);
627                 mnt_drop_write(path.mnt);
628         }
629         path_put(&path);
630         if (retry_estale(error, lookup_flags)) {
631                 lookup_flags |= LOOKUP_REVAL;
632                 goto retry;
633         }
634         return error;
635 }
636 
637 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
638                 const char __user *, name)
639 {
640         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
641 }
642 
643 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
644                 const char __user *, name)
645 {
646         return path_removexattr(pathname, name, 0);
647 }
648 
649 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
650 {
651         struct fd f = fdget(fd);
652         int error = -EBADF;
653 
654         if (!f.file)
655                 return error;
656         audit_file(f.file);
657         error = mnt_want_write_file(f.file);
658         if (!error) {
659                 error = removexattr(f.file->f_path.dentry, name);
660                 mnt_drop_write_file(f.file);
661         }
662         fdput(f);
663         return error;
664 }
665 
666 
667 static const char *
668 strcmp_prefix(const char *a, const char *a_prefix)
669 {
670         while (*a_prefix && *a == *a_prefix) {
671                 a++;
672                 a_prefix++;
673         }
674         return *a_prefix ? NULL : a;
675 }
676 
677 /*
678  * In order to implement different sets of xattr operations for each xattr
679  * prefix with the generic xattr API, a filesystem should create a
680  * null-terminated array of struct xattr_handler (one for each prefix) and
681  * hang a pointer to it off of the s_xattr field of the superblock.
682  *
683  * The generic_fooxattr() functions will use this list to dispatch xattr
684  * operations to the correct xattr_handler.
685  */
686 #define for_each_xattr_handler(handlers, handler)               \
687                 for ((handler) = *(handlers)++;                 \
688                         (handler) != NULL;                      \
689                         (handler) = *(handlers)++)
690 
691 /*
692  * Find the xattr_handler with the matching prefix.
693  */
694 static const struct xattr_handler *
695 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
696 {
697         const struct xattr_handler *handler;
698 
699         if (!*name)
700                 return NULL;
701 
702         for_each_xattr_handler(handlers, handler) {
703                 const char *n = strcmp_prefix(*name, handler->prefix);
704                 if (n) {
705                         *name = n;
706                         break;
707                 }
708         }
709         return handler;
710 }
711 
712 /*
713  * Find the handler for the prefix and dispatch its get() operation.
714  */
715 ssize_t
716 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
717 {
718         const struct xattr_handler *handler;
719 
720         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
721         if (!handler)
722                 return -EOPNOTSUPP;
723         return handler->get(dentry, name, buffer, size, handler->flags);
724 }
725 
726 /*
727  * Combine the results of the list() operation from every xattr_handler in the
728  * list.
729  */
730 ssize_t
731 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
732 {
733         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
734         unsigned int size = 0;
735 
736         if (!buffer) {
737                 for_each_xattr_handler(handlers, handler) {
738                         size += handler->list(dentry, NULL, 0, NULL, 0,
739                                               handler->flags);
740                 }
741         } else {
742                 char *buf = buffer;
743 
744                 for_each_xattr_handler(handlers, handler) {
745                         size = handler->list(dentry, buf, buffer_size,
746                                              NULL, 0, handler->flags);
747                         if (size > buffer_size)
748                                 return -ERANGE;
749                         buf += size;
750                         buffer_size -= size;
751                 }
752                 size = buf - buffer;
753         }
754         return size;
755 }
756 
757 /*
758  * Find the handler for the prefix and dispatch its set() operation.
759  */
760 int
761 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
762 {
763         const struct xattr_handler *handler;
764 
765         if (size == 0)
766                 value = "";  /* empty EA, do not remove */
767         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
768         if (!handler)
769                 return -EOPNOTSUPP;
770         return handler->set(dentry, name, value, size, flags, handler->flags);
771 }
772 
773 /*
774  * Find the handler for the prefix and dispatch its set() operation to remove
775  * any associated extended attribute.
776  */
777 int
778 generic_removexattr(struct dentry *dentry, const char *name)
779 {
780         const struct xattr_handler *handler;
781 
782         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
783         if (!handler)
784                 return -EOPNOTSUPP;
785         return handler->set(dentry, name, NULL, 0,
786                             XATTR_REPLACE, handler->flags);
787 }
788 
789 EXPORT_SYMBOL(generic_getxattr);
790 EXPORT_SYMBOL(generic_listxattr);
791 EXPORT_SYMBOL(generic_setxattr);
792 EXPORT_SYMBOL(generic_removexattr);
793 
794 /*
795  * Allocate new xattr and copy in the value; but leave the name to callers.
796  */
797 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
798 {
799         struct simple_xattr *new_xattr;
800         size_t len;
801 
802         /* wrap around? */
803         len = sizeof(*new_xattr) + size;
804         if (len < sizeof(*new_xattr))
805                 return NULL;
806 
807         new_xattr = kmalloc(len, GFP_KERNEL);
808         if (!new_xattr)
809                 return NULL;
810 
811         new_xattr->size = size;
812         memcpy(new_xattr->value, value, size);
813         return new_xattr;
814 }
815 
816 /*
817  * xattr GET operation for in-memory/pseudo filesystems
818  */
819 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
820                      void *buffer, size_t size)
821 {
822         struct simple_xattr *xattr;
823         int ret = -ENODATA;
824 
825         spin_lock(&xattrs->lock);
826         list_for_each_entry(xattr, &xattrs->head, list) {
827                 if (strcmp(name, xattr->name))
828                         continue;
829 
830                 ret = xattr->size;
831                 if (buffer) {
832                         if (size < xattr->size)
833                                 ret = -ERANGE;
834                         else
835                                 memcpy(buffer, xattr->value, xattr->size);
836                 }
837                 break;
838         }
839         spin_unlock(&xattrs->lock);
840         return ret;
841 }
842 
843 static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
844                               const void *value, size_t size, int flags)
845 {
846         struct simple_xattr *xattr;
847         struct simple_xattr *new_xattr = NULL;
848         int err = 0;
849 
850         /* value == NULL means remove */
851         if (value) {
852                 new_xattr = simple_xattr_alloc(value, size);
853                 if (!new_xattr)
854                         return -ENOMEM;
855 
856                 new_xattr->name = kstrdup(name, GFP_KERNEL);
857                 if (!new_xattr->name) {
858                         kfree(new_xattr);
859                         return -ENOMEM;
860                 }
861         }
862 
863         spin_lock(&xattrs->lock);
864         list_for_each_entry(xattr, &xattrs->head, list) {
865                 if (!strcmp(name, xattr->name)) {
866                         if (flags & XATTR_CREATE) {
867                                 xattr = new_xattr;
868                                 err = -EEXIST;
869                         } else if (new_xattr) {
870                                 list_replace(&xattr->list, &new_xattr->list);
871                         } else {
872                                 list_del(&xattr->list);
873                         }
874                         goto out;
875                 }
876         }
877         if (flags & XATTR_REPLACE) {
878                 xattr = new_xattr;
879                 err = -ENODATA;
880         } else {
881                 list_add(&new_xattr->list, &xattrs->head);
882                 xattr = NULL;
883         }
884 out:
885         spin_unlock(&xattrs->lock);
886         if (xattr) {
887                 kfree(xattr->name);
888                 kfree(xattr);
889         }
890         return err;
891 
892 }
893 
894 /**
895  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
896  * @xattrs: target simple_xattr list
897  * @name: name of the new extended attribute
898  * @value: value of the new xattr. If %NULL, will remove the attribute
899  * @size: size of the new xattr
900  * @flags: %XATTR_{CREATE|REPLACE}
901  *
902  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
903  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
904  * otherwise, fails with -ENODATA.
905  *
906  * Returns 0 on success, -errno on failure.
907  */
908 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
909                      const void *value, size_t size, int flags)
910 {
911         if (size == 0)
912                 value = ""; /* empty EA, do not remove */
913         return __simple_xattr_set(xattrs, name, value, size, flags);
914 }
915 
916 /*
917  * xattr REMOVE operation for in-memory/pseudo filesystems
918  */
919 int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
920 {
921         return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
922 }
923 
924 static bool xattr_is_trusted(const char *name)
925 {
926         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
927 }
928 
929 /*
930  * xattr LIST operation for in-memory/pseudo filesystems
931  */
932 ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
933                           size_t size)
934 {
935         bool trusted = capable(CAP_SYS_ADMIN);
936         struct simple_xattr *xattr;
937         size_t used = 0;
938 
939         spin_lock(&xattrs->lock);
940         list_for_each_entry(xattr, &xattrs->head, list) {
941                 size_t len;
942 
943                 /* skip "trusted." attributes for unprivileged callers */
944                 if (!trusted && xattr_is_trusted(xattr->name))
945                         continue;
946 
947                 len = strlen(xattr->name) + 1;
948                 used += len;
949                 if (buffer) {
950                         if (size < used) {
951                                 used = -ERANGE;
952                                 break;
953                         }
954                         memcpy(buffer, xattr->name, len);
955                         buffer += len;
956                 }
957         }
958         spin_unlock(&xattrs->lock);
959 
960         return used;
961 }
962 
963 /*
964  * Adds an extended attribute to the list
965  */
966 void simple_xattr_list_add(struct simple_xattrs *xattrs,
967                            struct simple_xattr *new_xattr)
968 {
969         spin_lock(&xattrs->lock);
970         list_add(&new_xattr->list, &xattrs->head);
971         spin_unlock(&xattrs->lock);
972 }
973 

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