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Linux/security/keys/keyctl.c

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  1 /* Userspace key control operations
  2  *
  3  * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
  4  * Written by David Howells (dhowells@redhat.com)
  5  *
  6  * This program is free software; you can redistribute it and/or
  7  * modify it under the terms of the GNU General Public License
  8  * as published by the Free Software Foundation; either version
  9  * 2 of the License, or (at your option) any later version.
 10  */
 11 
 12 #include <linux/module.h>
 13 #include <linux/init.h>
 14 #include <linux/sched.h>
 15 #include <linux/slab.h>
 16 #include <linux/syscalls.h>
 17 #include <linux/key.h>
 18 #include <linux/keyctl.h>
 19 #include <linux/fs.h>
 20 #include <linux/capability.h>
 21 #include <linux/string.h>
 22 #include <linux/err.h>
 23 #include <linux/vmalloc.h>
 24 #include <linux/security.h>
 25 #include <linux/uio.h>
 26 #include <asm/uaccess.h>
 27 #include "internal.h"
 28 
 29 #define KEY_MAX_DESC_SIZE 4096
 30 
 31 static int key_get_type_from_user(char *type,
 32                                   const char __user *_type,
 33                                   unsigned len)
 34 {
 35         int ret;
 36 
 37         ret = strncpy_from_user(type, _type, len);
 38         if (ret < 0)
 39                 return ret;
 40         if (ret == 0 || ret >= len)
 41                 return -EINVAL;
 42         if (type[0] == '.')
 43                 return -EPERM;
 44         type[len - 1] = '\0';
 45         return 0;
 46 }
 47 
 48 /*
 49  * Extract the description of a new key from userspace and either add it as a
 50  * new key to the specified keyring or update a matching key in that keyring.
 51  *
 52  * If the description is NULL or an empty string, the key type is asked to
 53  * generate one from the payload.
 54  *
 55  * The keyring must be writable so that we can attach the key to it.
 56  *
 57  * If successful, the new key's serial number is returned, otherwise an error
 58  * code is returned.
 59  */
 60 SYSCALL_DEFINE5(add_key, const char __user *, _type,
 61                 const char __user *, _description,
 62                 const void __user *, _payload,
 63                 size_t, plen,
 64                 key_serial_t, ringid)
 65 {
 66         key_ref_t keyring_ref, key_ref;
 67         char type[32], *description;
 68         void *payload;
 69         long ret;
 70 
 71         ret = -EINVAL;
 72         if (plen > 1024 * 1024 - 1)
 73                 goto error;
 74 
 75         /* draw all the data into kernel space */
 76         ret = key_get_type_from_user(type, _type, sizeof(type));
 77         if (ret < 0)
 78                 goto error;
 79 
 80         description = NULL;
 81         if (_description) {
 82                 description = strndup_user(_description, KEY_MAX_DESC_SIZE);
 83                 if (IS_ERR(description)) {
 84                         ret = PTR_ERR(description);
 85                         goto error;
 86                 }
 87                 if (!*description) {
 88                         kfree(description);
 89                         description = NULL;
 90                 } else if ((description[0] == '.') &&
 91                            (strncmp(type, "keyring", 7) == 0)) {
 92                         ret = -EPERM;
 93                         goto error2;
 94                 }
 95         }
 96 
 97         /* pull the payload in if one was supplied */
 98         payload = NULL;
 99 
100         if (_payload) {
101                 ret = -ENOMEM;
102                 payload = kmalloc(plen, GFP_KERNEL | __GFP_NOWARN);
103                 if (!payload) {
104                         if (plen <= PAGE_SIZE)
105                                 goto error2;
106                         payload = vmalloc(plen);
107                         if (!payload)
108                                 goto error2;
109                 }
110 
111                 ret = -EFAULT;
112                 if (copy_from_user(payload, _payload, plen) != 0)
113                         goto error3;
114         }
115 
116         /* find the target keyring (which must be writable) */
117         keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
118         if (IS_ERR(keyring_ref)) {
119                 ret = PTR_ERR(keyring_ref);
120                 goto error3;
121         }
122 
123         /* create or update the requested key and add it to the target
124          * keyring */
125         key_ref = key_create_or_update(keyring_ref, type, description,
126                                        payload, plen, KEY_PERM_UNDEF,
127                                        KEY_ALLOC_IN_QUOTA);
128         if (!IS_ERR(key_ref)) {
129                 ret = key_ref_to_ptr(key_ref)->serial;
130                 key_ref_put(key_ref);
131         }
132         else {
133                 ret = PTR_ERR(key_ref);
134         }
135 
136         key_ref_put(keyring_ref);
137  error3:
138         kvfree(payload);
139  error2:
140         kfree(description);
141  error:
142         return ret;
143 }
144 
145 /*
146  * Search the process keyrings and keyring trees linked from those for a
147  * matching key.  Keyrings must have appropriate Search permission to be
148  * searched.
149  *
150  * If a key is found, it will be attached to the destination keyring if there's
151  * one specified and the serial number of the key will be returned.
152  *
153  * If no key is found, /sbin/request-key will be invoked if _callout_info is
154  * non-NULL in an attempt to create a key.  The _callout_info string will be
155  * passed to /sbin/request-key to aid with completing the request.  If the
156  * _callout_info string is "" then it will be changed to "-".
157  */
158 SYSCALL_DEFINE4(request_key, const char __user *, _type,
159                 const char __user *, _description,
160                 const char __user *, _callout_info,
161                 key_serial_t, destringid)
162 {
163         struct key_type *ktype;
164         struct key *key;
165         key_ref_t dest_ref;
166         size_t callout_len;
167         char type[32], *description, *callout_info;
168         long ret;
169 
170         /* pull the type into kernel space */
171         ret = key_get_type_from_user(type, _type, sizeof(type));
172         if (ret < 0)
173                 goto error;
174 
175         /* pull the description into kernel space */
176         description = strndup_user(_description, KEY_MAX_DESC_SIZE);
177         if (IS_ERR(description)) {
178                 ret = PTR_ERR(description);
179                 goto error;
180         }
181 
182         /* pull the callout info into kernel space */
183         callout_info = NULL;
184         callout_len = 0;
185         if (_callout_info) {
186                 callout_info = strndup_user(_callout_info, PAGE_SIZE);
187                 if (IS_ERR(callout_info)) {
188                         ret = PTR_ERR(callout_info);
189                         goto error2;
190                 }
191                 callout_len = strlen(callout_info);
192         }
193 
194         /* get the destination keyring if specified */
195         dest_ref = NULL;
196         if (destringid) {
197                 dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
198                                            KEY_NEED_WRITE);
199                 if (IS_ERR(dest_ref)) {
200                         ret = PTR_ERR(dest_ref);
201                         goto error3;
202                 }
203         }
204 
205         /* find the key type */
206         ktype = key_type_lookup(type);
207         if (IS_ERR(ktype)) {
208                 ret = PTR_ERR(ktype);
209                 goto error4;
210         }
211 
212         /* do the search */
213         key = request_key_and_link(ktype, description, callout_info,
214                                    callout_len, NULL, key_ref_to_ptr(dest_ref),
215                                    KEY_ALLOC_IN_QUOTA);
216         if (IS_ERR(key)) {
217                 ret = PTR_ERR(key);
218                 goto error5;
219         }
220 
221         /* wait for the key to finish being constructed */
222         ret = wait_for_key_construction(key, 1);
223         if (ret < 0)
224                 goto error6;
225 
226         ret = key->serial;
227 
228 error6:
229         key_put(key);
230 error5:
231         key_type_put(ktype);
232 error4:
233         key_ref_put(dest_ref);
234 error3:
235         kfree(callout_info);
236 error2:
237         kfree(description);
238 error:
239         return ret;
240 }
241 
242 /*
243  * Get the ID of the specified process keyring.
244  *
245  * The requested keyring must have search permission to be found.
246  *
247  * If successful, the ID of the requested keyring will be returned.
248  */
249 long keyctl_get_keyring_ID(key_serial_t id, int create)
250 {
251         key_ref_t key_ref;
252         unsigned long lflags;
253         long ret;
254 
255         lflags = create ? KEY_LOOKUP_CREATE : 0;
256         key_ref = lookup_user_key(id, lflags, KEY_NEED_SEARCH);
257         if (IS_ERR(key_ref)) {
258                 ret = PTR_ERR(key_ref);
259                 goto error;
260         }
261 
262         ret = key_ref_to_ptr(key_ref)->serial;
263         key_ref_put(key_ref);
264 error:
265         return ret;
266 }
267 
268 /*
269  * Join a (named) session keyring.
270  *
271  * Create and join an anonymous session keyring or join a named session
272  * keyring, creating it if necessary.  A named session keyring must have Search
273  * permission for it to be joined.  Session keyrings without this permit will
274  * be skipped over.
275  *
276  * If successful, the ID of the joined session keyring will be returned.
277  */
278 long keyctl_join_session_keyring(const char __user *_name)
279 {
280         char *name;
281         long ret;
282 
283         /* fetch the name from userspace */
284         name = NULL;
285         if (_name) {
286                 name = strndup_user(_name, KEY_MAX_DESC_SIZE);
287                 if (IS_ERR(name)) {
288                         ret = PTR_ERR(name);
289                         goto error;
290                 }
291         }
292 
293         /* join the session */
294         ret = join_session_keyring(name);
295         kfree(name);
296 
297 error:
298         return ret;
299 }
300 
301 /*
302  * Update a key's data payload from the given data.
303  *
304  * The key must grant the caller Write permission and the key type must support
305  * updating for this to work.  A negative key can be positively instantiated
306  * with this call.
307  *
308  * If successful, 0 will be returned.  If the key type does not support
309  * updating, then -EOPNOTSUPP will be returned.
310  */
311 long keyctl_update_key(key_serial_t id,
312                        const void __user *_payload,
313                        size_t plen)
314 {
315         key_ref_t key_ref;
316         void *payload;
317         long ret;
318 
319         ret = -EINVAL;
320         if (plen > PAGE_SIZE)
321                 goto error;
322 
323         /* pull the payload in if one was supplied */
324         payload = NULL;
325         if (_payload) {
326                 ret = -ENOMEM;
327                 payload = kmalloc(plen, GFP_KERNEL);
328                 if (!payload)
329                         goto error;
330 
331                 ret = -EFAULT;
332                 if (copy_from_user(payload, _payload, plen) != 0)
333                         goto error2;
334         }
335 
336         /* find the target key (which must be writable) */
337         key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
338         if (IS_ERR(key_ref)) {
339                 ret = PTR_ERR(key_ref);
340                 goto error2;
341         }
342 
343         /* update the key */
344         ret = key_update(key_ref, payload, plen);
345 
346         key_ref_put(key_ref);
347 error2:
348         kfree(payload);
349 error:
350         return ret;
351 }
352 
353 /*
354  * Revoke a key.
355  *
356  * The key must be grant the caller Write or Setattr permission for this to
357  * work.  The key type should give up its quota claim when revoked.  The key
358  * and any links to the key will be automatically garbage collected after a
359  * certain amount of time (/proc/sys/kernel/keys/gc_delay).
360  *
361  * Keys with KEY_FLAG_KEEP set should not be revoked.
362  *
363  * If successful, 0 is returned.
364  */
365 long keyctl_revoke_key(key_serial_t id)
366 {
367         key_ref_t key_ref;
368         struct key *key;
369         long ret;
370 
371         key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
372         if (IS_ERR(key_ref)) {
373                 ret = PTR_ERR(key_ref);
374                 if (ret != -EACCES)
375                         goto error;
376                 key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
377                 if (IS_ERR(key_ref)) {
378                         ret = PTR_ERR(key_ref);
379                         goto error;
380                 }
381         }
382 
383         key = key_ref_to_ptr(key_ref);
384         ret = 0;
385         if (test_bit(KEY_FLAG_KEEP, &key->flags))
386                 ret = -EPERM;
387         else
388                 key_revoke(key);
389 
390         key_ref_put(key_ref);
391 error:
392         return ret;
393 }
394 
395 /*
396  * Invalidate a key.
397  *
398  * The key must be grant the caller Invalidate permission for this to work.
399  * The key and any links to the key will be automatically garbage collected
400  * immediately.
401  *
402  * Keys with KEY_FLAG_KEEP set should not be invalidated.
403  *
404  * If successful, 0 is returned.
405  */
406 long keyctl_invalidate_key(key_serial_t id)
407 {
408         key_ref_t key_ref;
409         struct key *key;
410         long ret;
411 
412         kenter("%d", id);
413 
414         key_ref = lookup_user_key(id, 0, KEY_NEED_SEARCH);
415         if (IS_ERR(key_ref)) {
416                 ret = PTR_ERR(key_ref);
417 
418                 /* Root is permitted to invalidate certain special keys */
419                 if (capable(CAP_SYS_ADMIN)) {
420                         key_ref = lookup_user_key(id, 0, 0);
421                         if (IS_ERR(key_ref))
422                                 goto error;
423                         if (test_bit(KEY_FLAG_ROOT_CAN_INVAL,
424                                      &key_ref_to_ptr(key_ref)->flags))
425                                 goto invalidate;
426                         goto error_put;
427                 }
428 
429                 goto error;
430         }
431 
432 invalidate:
433         key = key_ref_to_ptr(key_ref);
434         ret = 0;
435         if (test_bit(KEY_FLAG_KEEP, &key->flags))
436                 ret = -EPERM;
437         else
438                 key_invalidate(key);
439 error_put:
440         key_ref_put(key_ref);
441 error:
442         kleave(" = %ld", ret);
443         return ret;
444 }
445 
446 /*
447  * Clear the specified keyring, creating an empty process keyring if one of the
448  * special keyring IDs is used.
449  *
450  * The keyring must grant the caller Write permission and not have
451  * KEY_FLAG_KEEP set for this to work.  If successful, 0 will be returned.
452  */
453 long keyctl_keyring_clear(key_serial_t ringid)
454 {
455         key_ref_t keyring_ref;
456         struct key *keyring;
457         long ret;
458 
459         keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
460         if (IS_ERR(keyring_ref)) {
461                 ret = PTR_ERR(keyring_ref);
462 
463                 /* Root is permitted to invalidate certain special keyrings */
464                 if (capable(CAP_SYS_ADMIN)) {
465                         keyring_ref = lookup_user_key(ringid, 0, 0);
466                         if (IS_ERR(keyring_ref))
467                                 goto error;
468                         if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
469                                      &key_ref_to_ptr(keyring_ref)->flags))
470                                 goto clear;
471                         goto error_put;
472                 }
473 
474                 goto error;
475         }
476 
477 clear:
478         keyring = key_ref_to_ptr(keyring_ref);
479         if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
480                 ret = -EPERM;
481         else
482                 ret = keyring_clear(keyring);
483 error_put:
484         key_ref_put(keyring_ref);
485 error:
486         return ret;
487 }
488 
489 /*
490  * Create a link from a keyring to a key if there's no matching key in the
491  * keyring, otherwise replace the link to the matching key with a link to the
492  * new key.
493  *
494  * The key must grant the caller Link permission and the the keyring must grant
495  * the caller Write permission.  Furthermore, if an additional link is created,
496  * the keyring's quota will be extended.
497  *
498  * If successful, 0 will be returned.
499  */
500 long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
501 {
502         key_ref_t keyring_ref, key_ref;
503         long ret;
504 
505         keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
506         if (IS_ERR(keyring_ref)) {
507                 ret = PTR_ERR(keyring_ref);
508                 goto error;
509         }
510 
511         key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_LINK);
512         if (IS_ERR(key_ref)) {
513                 ret = PTR_ERR(key_ref);
514                 goto error2;
515         }
516 
517         ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
518 
519         key_ref_put(key_ref);
520 error2:
521         key_ref_put(keyring_ref);
522 error:
523         return ret;
524 }
525 
526 /*
527  * Unlink a key from a keyring.
528  *
529  * The keyring must grant the caller Write permission for this to work; the key
530  * itself need not grant the caller anything.  If the last link to a key is
531  * removed then that key will be scheduled for destruction.
532  *
533  * Keys or keyrings with KEY_FLAG_KEEP set should not be unlinked.
534  *
535  * If successful, 0 will be returned.
536  */
537 long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
538 {
539         key_ref_t keyring_ref, key_ref;
540         struct key *keyring, *key;
541         long ret;
542 
543         keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_WRITE);
544         if (IS_ERR(keyring_ref)) {
545                 ret = PTR_ERR(keyring_ref);
546                 goto error;
547         }
548 
549         key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 0);
550         if (IS_ERR(key_ref)) {
551                 ret = PTR_ERR(key_ref);
552                 goto error2;
553         }
554 
555         keyring = key_ref_to_ptr(keyring_ref);
556         key = key_ref_to_ptr(key_ref);
557         if (test_bit(KEY_FLAG_KEEP, &keyring->flags) &&
558             test_bit(KEY_FLAG_KEEP, &key->flags))
559                 ret = -EPERM;
560         else
561                 ret = key_unlink(keyring, key);
562 
563         key_ref_put(key_ref);
564 error2:
565         key_ref_put(keyring_ref);
566 error:
567         return ret;
568 }
569 
570 /*
571  * Return a description of a key to userspace.
572  *
573  * The key must grant the caller View permission for this to work.
574  *
575  * If there's a buffer, we place up to buflen bytes of data into it formatted
576  * in the following way:
577  *
578  *      type;uid;gid;perm;description<NUL>
579  *
580  * If successful, we return the amount of description available, irrespective
581  * of how much we may have copied into the buffer.
582  */
583 long keyctl_describe_key(key_serial_t keyid,
584                          char __user *buffer,
585                          size_t buflen)
586 {
587         struct key *key, *instkey;
588         key_ref_t key_ref;
589         char *infobuf;
590         long ret;
591         int desclen, infolen;
592 
593         key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_VIEW);
594         if (IS_ERR(key_ref)) {
595                 /* viewing a key under construction is permitted if we have the
596                  * authorisation token handy */
597                 if (PTR_ERR(key_ref) == -EACCES) {
598                         instkey = key_get_instantiation_authkey(keyid);
599                         if (!IS_ERR(instkey)) {
600                                 key_put(instkey);
601                                 key_ref = lookup_user_key(keyid,
602                                                           KEY_LOOKUP_PARTIAL,
603                                                           0);
604                                 if (!IS_ERR(key_ref))
605                                         goto okay;
606                         }
607                 }
608 
609                 ret = PTR_ERR(key_ref);
610                 goto error;
611         }
612 
613 okay:
614         key = key_ref_to_ptr(key_ref);
615         desclen = strlen(key->description);
616 
617         /* calculate how much information we're going to return */
618         ret = -ENOMEM;
619         infobuf = kasprintf(GFP_KERNEL,
620                             "%s;%d;%d;%08x;",
621                             key->type->name,
622                             from_kuid_munged(current_user_ns(), key->uid),
623                             from_kgid_munged(current_user_ns(), key->gid),
624                             key->perm);
625         if (!infobuf)
626                 goto error2;
627         infolen = strlen(infobuf);
628         ret = infolen + desclen + 1;
629 
630         /* consider returning the data */
631         if (buffer && buflen >= ret) {
632                 if (copy_to_user(buffer, infobuf, infolen) != 0 ||
633                     copy_to_user(buffer + infolen, key->description,
634                                  desclen + 1) != 0)
635                         ret = -EFAULT;
636         }
637 
638         kfree(infobuf);
639 error2:
640         key_ref_put(key_ref);
641 error:
642         return ret;
643 }
644 
645 /*
646  * Search the specified keyring and any keyrings it links to for a matching
647  * key.  Only keyrings that grant the caller Search permission will be searched
648  * (this includes the starting keyring).  Only keys with Search permission can
649  * be found.
650  *
651  * If successful, the found key will be linked to the destination keyring if
652  * supplied and the key has Link permission, and the found key ID will be
653  * returned.
654  */
655 long keyctl_keyring_search(key_serial_t ringid,
656                            const char __user *_type,
657                            const char __user *_description,
658                            key_serial_t destringid)
659 {
660         struct key_type *ktype;
661         key_ref_t keyring_ref, key_ref, dest_ref;
662         char type[32], *description;
663         long ret;
664 
665         /* pull the type and description into kernel space */
666         ret = key_get_type_from_user(type, _type, sizeof(type));
667         if (ret < 0)
668                 goto error;
669 
670         description = strndup_user(_description, KEY_MAX_DESC_SIZE);
671         if (IS_ERR(description)) {
672                 ret = PTR_ERR(description);
673                 goto error;
674         }
675 
676         /* get the keyring at which to begin the search */
677         keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_SEARCH);
678         if (IS_ERR(keyring_ref)) {
679                 ret = PTR_ERR(keyring_ref);
680                 goto error2;
681         }
682 
683         /* get the destination keyring if specified */
684         dest_ref = NULL;
685         if (destringid) {
686                 dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
687                                            KEY_NEED_WRITE);
688                 if (IS_ERR(dest_ref)) {
689                         ret = PTR_ERR(dest_ref);
690                         goto error3;
691                 }
692         }
693 
694         /* find the key type */
695         ktype = key_type_lookup(type);
696         if (IS_ERR(ktype)) {
697                 ret = PTR_ERR(ktype);
698                 goto error4;
699         }
700 
701         /* do the search */
702         key_ref = keyring_search(keyring_ref, ktype, description);
703         if (IS_ERR(key_ref)) {
704                 ret = PTR_ERR(key_ref);
705 
706                 /* treat lack or presence of a negative key the same */
707                 if (ret == -EAGAIN)
708                         ret = -ENOKEY;
709                 goto error5;
710         }
711 
712         /* link the resulting key to the destination keyring if we can */
713         if (dest_ref) {
714                 ret = key_permission(key_ref, KEY_NEED_LINK);
715                 if (ret < 0)
716                         goto error6;
717 
718                 ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
719                 if (ret < 0)
720                         goto error6;
721         }
722 
723         ret = key_ref_to_ptr(key_ref)->serial;
724 
725 error6:
726         key_ref_put(key_ref);
727 error5:
728         key_type_put(ktype);
729 error4:
730         key_ref_put(dest_ref);
731 error3:
732         key_ref_put(keyring_ref);
733 error2:
734         kfree(description);
735 error:
736         return ret;
737 }
738 
739 /*
740  * Read a key's payload.
741  *
742  * The key must either grant the caller Read permission, or it must grant the
743  * caller Search permission when searched for from the process keyrings.
744  *
745  * If successful, we place up to buflen bytes of data into the buffer, if one
746  * is provided, and return the amount of data that is available in the key,
747  * irrespective of how much we copied into the buffer.
748  */
749 long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
750 {
751         struct key *key;
752         key_ref_t key_ref;
753         long ret;
754 
755         /* find the key first */
756         key_ref = lookup_user_key(keyid, 0, 0);
757         if (IS_ERR(key_ref)) {
758                 ret = -ENOKEY;
759                 goto error;
760         }
761 
762         key = key_ref_to_ptr(key_ref);
763 
764         /* see if we can read it directly */
765         ret = key_permission(key_ref, KEY_NEED_READ);
766         if (ret == 0)
767                 goto can_read_key;
768         if (ret != -EACCES)
769                 goto error;
770 
771         /* we can't; see if it's searchable from this process's keyrings
772          * - we automatically take account of the fact that it may be
773          *   dangling off an instantiation key
774          */
775         if (!is_key_possessed(key_ref)) {
776                 ret = -EACCES;
777                 goto error2;
778         }
779 
780         /* the key is probably readable - now try to read it */
781 can_read_key:
782         ret = -EOPNOTSUPP;
783         if (key->type->read) {
784                 /* Read the data with the semaphore held (since we might sleep)
785                  * to protect against the key being updated or revoked.
786                  */
787                 down_read(&key->sem);
788                 ret = key_validate(key);
789                 if (ret == 0)
790                         ret = key->type->read(key, buffer, buflen);
791                 up_read(&key->sem);
792         }
793 
794 error2:
795         key_put(key);
796 error:
797         return ret;
798 }
799 
800 /*
801  * Change the ownership of a key
802  *
803  * The key must grant the caller Setattr permission for this to work, though
804  * the key need not be fully instantiated yet.  For the UID to be changed, or
805  * for the GID to be changed to a group the caller is not a member of, the
806  * caller must have sysadmin capability.  If either uid or gid is -1 then that
807  * attribute is not changed.
808  *
809  * If the UID is to be changed, the new user must have sufficient quota to
810  * accept the key.  The quota deduction will be removed from the old user to
811  * the new user should the attribute be changed.
812  *
813  * If successful, 0 will be returned.
814  */
815 long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
816 {
817         struct key_user *newowner, *zapowner = NULL;
818         struct key *key;
819         key_ref_t key_ref;
820         long ret;
821         kuid_t uid;
822         kgid_t gid;
823 
824         uid = make_kuid(current_user_ns(), user);
825         gid = make_kgid(current_user_ns(), group);
826         ret = -EINVAL;
827         if ((user != (uid_t) -1) && !uid_valid(uid))
828                 goto error;
829         if ((group != (gid_t) -1) && !gid_valid(gid))
830                 goto error;
831 
832         ret = 0;
833         if (user == (uid_t) -1 && group == (gid_t) -1)
834                 goto error;
835 
836         key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
837                                   KEY_NEED_SETATTR);
838         if (IS_ERR(key_ref)) {
839                 ret = PTR_ERR(key_ref);
840                 goto error;
841         }
842 
843         key = key_ref_to_ptr(key_ref);
844 
845         /* make the changes with the locks held to prevent chown/chown races */
846         ret = -EACCES;
847         down_write(&key->sem);
848 
849         if (!capable(CAP_SYS_ADMIN)) {
850                 /* only the sysadmin can chown a key to some other UID */
851                 if (user != (uid_t) -1 && !uid_eq(key->uid, uid))
852                         goto error_put;
853 
854                 /* only the sysadmin can set the key's GID to a group other
855                  * than one of those that the current process subscribes to */
856                 if (group != (gid_t) -1 && !gid_eq(gid, key->gid) && !in_group_p(gid))
857                         goto error_put;
858         }
859 
860         /* change the UID */
861         if (user != (uid_t) -1 && !uid_eq(uid, key->uid)) {
862                 ret = -ENOMEM;
863                 newowner = key_user_lookup(uid);
864                 if (!newowner)
865                         goto error_put;
866 
867                 /* transfer the quota burden to the new user */
868                 if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
869                         unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
870                                 key_quota_root_maxkeys : key_quota_maxkeys;
871                         unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
872                                 key_quota_root_maxbytes : key_quota_maxbytes;
873 
874                         spin_lock(&newowner->lock);
875                         if (newowner->qnkeys + 1 >= maxkeys ||
876                             newowner->qnbytes + key->quotalen >= maxbytes ||
877                             newowner->qnbytes + key->quotalen <
878                             newowner->qnbytes)
879                                 goto quota_overrun;
880 
881                         newowner->qnkeys++;
882                         newowner->qnbytes += key->quotalen;
883                         spin_unlock(&newowner->lock);
884 
885                         spin_lock(&key->user->lock);
886                         key->user->qnkeys--;
887                         key->user->qnbytes -= key->quotalen;
888                         spin_unlock(&key->user->lock);
889                 }
890 
891                 atomic_dec(&key->user->nkeys);
892                 atomic_inc(&newowner->nkeys);
893 
894                 if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
895                         atomic_dec(&key->user->nikeys);
896                         atomic_inc(&newowner->nikeys);
897                 }
898 
899                 zapowner = key->user;
900                 key->user = newowner;
901                 key->uid = uid;
902         }
903 
904         /* change the GID */
905         if (group != (gid_t) -1)
906                 key->gid = gid;
907 
908         ret = 0;
909 
910 error_put:
911         up_write(&key->sem);
912         key_put(key);
913         if (zapowner)
914                 key_user_put(zapowner);
915 error:
916         return ret;
917 
918 quota_overrun:
919         spin_unlock(&newowner->lock);
920         zapowner = newowner;
921         ret = -EDQUOT;
922         goto error_put;
923 }
924 
925 /*
926  * Change the permission mask on a key.
927  *
928  * The key must grant the caller Setattr permission for this to work, though
929  * the key need not be fully instantiated yet.  If the caller does not have
930  * sysadmin capability, it may only change the permission on keys that it owns.
931  */
932 long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
933 {
934         struct key *key;
935         key_ref_t key_ref;
936         long ret;
937 
938         ret = -EINVAL;
939         if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
940                 goto error;
941 
942         key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
943                                   KEY_NEED_SETATTR);
944         if (IS_ERR(key_ref)) {
945                 ret = PTR_ERR(key_ref);
946                 goto error;
947         }
948 
949         key = key_ref_to_ptr(key_ref);
950 
951         /* make the changes with the locks held to prevent chown/chmod races */
952         ret = -EACCES;
953         down_write(&key->sem);
954 
955         /* if we're not the sysadmin, we can only change a key that we own */
956         if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
957                 key->perm = perm;
958                 ret = 0;
959         }
960 
961         up_write(&key->sem);
962         key_put(key);
963 error:
964         return ret;
965 }
966 
967 /*
968  * Get the destination keyring for instantiation and check that the caller has
969  * Write permission on it.
970  */
971 static long get_instantiation_keyring(key_serial_t ringid,
972                                       struct request_key_auth *rka,
973                                       struct key **_dest_keyring)
974 {
975         key_ref_t dkref;
976 
977         *_dest_keyring = NULL;
978 
979         /* just return a NULL pointer if we weren't asked to make a link */
980         if (ringid == 0)
981                 return 0;
982 
983         /* if a specific keyring is nominated by ID, then use that */
984         if (ringid > 0) {
985                 dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
986                 if (IS_ERR(dkref))
987                         return PTR_ERR(dkref);
988                 *_dest_keyring = key_ref_to_ptr(dkref);
989                 return 0;
990         }
991 
992         if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
993                 return -EINVAL;
994 
995         /* otherwise specify the destination keyring recorded in the
996          * authorisation key (any KEY_SPEC_*_KEYRING) */
997         if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
998                 *_dest_keyring = key_get(rka->dest_keyring);
999                 return 0;
1000         }
1001 
1002         return -ENOKEY;
1003 }
1004 
1005 /*
1006  * Change the request_key authorisation key on the current process.
1007  */
1008 static int keyctl_change_reqkey_auth(struct key *key)
1009 {
1010         struct cred *new;
1011 
1012         new = prepare_creds();
1013         if (!new)
1014                 return -ENOMEM;
1015 
1016         key_put(new->request_key_auth);
1017         new->request_key_auth = key_get(key);
1018 
1019         return commit_creds(new);
1020 }
1021 
1022 /*
1023  * Instantiate a key with the specified payload and link the key into the
1024  * destination keyring if one is given.
1025  *
1026  * The caller must have the appropriate instantiation permit set for this to
1027  * work (see keyctl_assume_authority).  No other permissions are required.
1028  *
1029  * If successful, 0 will be returned.
1030  */
1031 long keyctl_instantiate_key_common(key_serial_t id,
1032                                    struct iov_iter *from,
1033                                    key_serial_t ringid)
1034 {
1035         const struct cred *cred = current_cred();
1036         struct request_key_auth *rka;
1037         struct key *instkey, *dest_keyring;
1038         size_t plen = from ? iov_iter_count(from) : 0;
1039         void *payload;
1040         long ret;
1041 
1042         kenter("%d,,%zu,%d", id, plen, ringid);
1043 
1044         if (!plen)
1045                 from = NULL;
1046 
1047         ret = -EINVAL;
1048         if (plen > 1024 * 1024 - 1)
1049                 goto error;
1050 
1051         /* the appropriate instantiation authorisation key must have been
1052          * assumed before calling this */
1053         ret = -EPERM;
1054         instkey = cred->request_key_auth;
1055         if (!instkey)
1056                 goto error;
1057 
1058         rka = instkey->payload.data[0];
1059         if (rka->target_key->serial != id)
1060                 goto error;
1061 
1062         /* pull the payload in if one was supplied */
1063         payload = NULL;
1064 
1065         if (from) {
1066                 ret = -ENOMEM;
1067                 payload = kmalloc(plen, GFP_KERNEL);
1068                 if (!payload) {
1069                         if (plen <= PAGE_SIZE)
1070                                 goto error;
1071                         payload = vmalloc(plen);
1072                         if (!payload)
1073                                 goto error;
1074                 }
1075 
1076                 ret = -EFAULT;
1077                 if (copy_from_iter(payload, plen, from) != plen)
1078                         goto error2;
1079         }
1080 
1081         /* find the destination keyring amongst those belonging to the
1082          * requesting task */
1083         ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1084         if (ret < 0)
1085                 goto error2;
1086 
1087         /* instantiate the key and link it into a keyring */
1088         ret = key_instantiate_and_link(rka->target_key, payload, plen,
1089                                        dest_keyring, instkey);
1090 
1091         key_put(dest_keyring);
1092 
1093         /* discard the assumed authority if it's just been disabled by
1094          * instantiation of the key */
1095         if (ret == 0)
1096                 keyctl_change_reqkey_auth(NULL);
1097 
1098 error2:
1099         kvfree(payload);
1100 error:
1101         return ret;
1102 }
1103 
1104 /*
1105  * Instantiate a key with the specified payload and link the key into the
1106  * destination keyring if one is given.
1107  *
1108  * The caller must have the appropriate instantiation permit set for this to
1109  * work (see keyctl_assume_authority).  No other permissions are required.
1110  *
1111  * If successful, 0 will be returned.
1112  */
1113 long keyctl_instantiate_key(key_serial_t id,
1114                             const void __user *_payload,
1115                             size_t plen,
1116                             key_serial_t ringid)
1117 {
1118         if (_payload && plen) {
1119                 struct iovec iov;
1120                 struct iov_iter from;
1121                 int ret;
1122 
1123                 ret = import_single_range(WRITE, (void __user *)_payload, plen,
1124                                           &iov, &from);
1125                 if (unlikely(ret))
1126                         return ret;
1127 
1128                 return keyctl_instantiate_key_common(id, &from, ringid);
1129         }
1130 
1131         return keyctl_instantiate_key_common(id, NULL, ringid);
1132 }
1133 
1134 /*
1135  * Instantiate a key with the specified multipart payload and link the key into
1136  * the destination keyring if one is given.
1137  *
1138  * The caller must have the appropriate instantiation permit set for this to
1139  * work (see keyctl_assume_authority).  No other permissions are required.
1140  *
1141  * If successful, 0 will be returned.
1142  */
1143 long keyctl_instantiate_key_iov(key_serial_t id,
1144                                 const struct iovec __user *_payload_iov,
1145                                 unsigned ioc,
1146                                 key_serial_t ringid)
1147 {
1148         struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
1149         struct iov_iter from;
1150         long ret;
1151 
1152         if (!_payload_iov)
1153                 ioc = 0;
1154 
1155         ret = import_iovec(WRITE, _payload_iov, ioc,
1156                                     ARRAY_SIZE(iovstack), &iov, &from);
1157         if (ret < 0)
1158                 return ret;
1159         ret = keyctl_instantiate_key_common(id, &from, ringid);
1160         kfree(iov);
1161         return ret;
1162 }
1163 
1164 /*
1165  * Negatively instantiate the key with the given timeout (in seconds) and link
1166  * the key into the destination keyring if one is given.
1167  *
1168  * The caller must have the appropriate instantiation permit set for this to
1169  * work (see keyctl_assume_authority).  No other permissions are required.
1170  *
1171  * The key and any links to the key will be automatically garbage collected
1172  * after the timeout expires.
1173  *
1174  * Negative keys are used to rate limit repeated request_key() calls by causing
1175  * them to return -ENOKEY until the negative key expires.
1176  *
1177  * If successful, 0 will be returned.
1178  */
1179 long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
1180 {
1181         return keyctl_reject_key(id, timeout, ENOKEY, ringid);
1182 }
1183 
1184 /*
1185  * Negatively instantiate the key with the given timeout (in seconds) and error
1186  * code and link the key into the destination keyring if one is given.
1187  *
1188  * The caller must have the appropriate instantiation permit set for this to
1189  * work (see keyctl_assume_authority).  No other permissions are required.
1190  *
1191  * The key and any links to the key will be automatically garbage collected
1192  * after the timeout expires.
1193  *
1194  * Negative keys are used to rate limit repeated request_key() calls by causing
1195  * them to return the specified error code until the negative key expires.
1196  *
1197  * If successful, 0 will be returned.
1198  */
1199 long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
1200                        key_serial_t ringid)
1201 {
1202         const struct cred *cred = current_cred();
1203         struct request_key_auth *rka;
1204         struct key *instkey, *dest_keyring;
1205         long ret;
1206 
1207         kenter("%d,%u,%u,%d", id, timeout, error, ringid);
1208 
1209         /* must be a valid error code and mustn't be a kernel special */
1210         if (error <= 0 ||
1211             error >= MAX_ERRNO ||
1212             error == ERESTARTSYS ||
1213             error == ERESTARTNOINTR ||
1214             error == ERESTARTNOHAND ||
1215             error == ERESTART_RESTARTBLOCK)
1216                 return -EINVAL;
1217 
1218         /* the appropriate instantiation authorisation key must have been
1219          * assumed before calling this */
1220         ret = -EPERM;
1221         instkey = cred->request_key_auth;
1222         if (!instkey)
1223                 goto error;
1224 
1225         rka = instkey->payload.data[0];
1226         if (rka->target_key->serial != id)
1227                 goto error;
1228 
1229         /* find the destination keyring if present (which must also be
1230          * writable) */
1231         ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1232         if (ret < 0)
1233                 goto error;
1234 
1235         /* instantiate the key and link it into a keyring */
1236         ret = key_reject_and_link(rka->target_key, timeout, error,
1237                                   dest_keyring, instkey);
1238 
1239         key_put(dest_keyring);
1240 
1241         /* discard the assumed authority if it's just been disabled by
1242          * instantiation of the key */
1243         if (ret == 0)
1244                 keyctl_change_reqkey_auth(NULL);
1245 
1246 error:
1247         return ret;
1248 }
1249 
1250 /*
1251  * Read or set the default keyring in which request_key() will cache keys and
1252  * return the old setting.
1253  *
1254  * If a process keyring is specified then this will be created if it doesn't
1255  * yet exist.  The old setting will be returned if successful.
1256  */
1257 long keyctl_set_reqkey_keyring(int reqkey_defl)
1258 {
1259         struct cred *new;
1260         int ret, old_setting;
1261 
1262         old_setting = current_cred_xxx(jit_keyring);
1263 
1264         if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
1265                 return old_setting;
1266 
1267         new = prepare_creds();
1268         if (!new)
1269                 return -ENOMEM;
1270 
1271         switch (reqkey_defl) {
1272         case KEY_REQKEY_DEFL_THREAD_KEYRING:
1273                 ret = install_thread_keyring_to_cred(new);
1274                 if (ret < 0)
1275                         goto error;
1276                 goto set;
1277 
1278         case KEY_REQKEY_DEFL_PROCESS_KEYRING:
1279                 ret = install_process_keyring_to_cred(new);
1280                 if (ret < 0) {
1281                         if (ret != -EEXIST)
1282                                 goto error;
1283                         ret = 0;
1284                 }
1285                 goto set;
1286 
1287         case KEY_REQKEY_DEFL_DEFAULT:
1288         case KEY_REQKEY_DEFL_SESSION_KEYRING:
1289         case KEY_REQKEY_DEFL_USER_KEYRING:
1290         case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
1291         case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
1292                 goto set;
1293 
1294         case KEY_REQKEY_DEFL_NO_CHANGE:
1295         case KEY_REQKEY_DEFL_GROUP_KEYRING:
1296         default:
1297                 ret = -EINVAL;
1298                 goto error;
1299         }
1300 
1301 set:
1302         new->jit_keyring = reqkey_defl;
1303         commit_creds(new);
1304         return old_setting;
1305 error:
1306         abort_creds(new);
1307         return ret;
1308 }
1309 
1310 /*
1311  * Set or clear the timeout on a key.
1312  *
1313  * Either the key must grant the caller Setattr permission or else the caller
1314  * must hold an instantiation authorisation token for the key.
1315  *
1316  * The timeout is either 0 to clear the timeout, or a number of seconds from
1317  * the current time.  The key and any links to the key will be automatically
1318  * garbage collected after the timeout expires.
1319  *
1320  * Keys with KEY_FLAG_KEEP set should not be timed out.
1321  *
1322  * If successful, 0 is returned.
1323  */
1324 long keyctl_set_timeout(key_serial_t id, unsigned timeout)
1325 {
1326         struct key *key, *instkey;
1327         key_ref_t key_ref;
1328         long ret;
1329 
1330         key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
1331                                   KEY_NEED_SETATTR);
1332         if (IS_ERR(key_ref)) {
1333                 /* setting the timeout on a key under construction is permitted
1334                  * if we have the authorisation token handy */
1335                 if (PTR_ERR(key_ref) == -EACCES) {
1336                         instkey = key_get_instantiation_authkey(id);
1337                         if (!IS_ERR(instkey)) {
1338                                 key_put(instkey);
1339                                 key_ref = lookup_user_key(id,
1340                                                           KEY_LOOKUP_PARTIAL,
1341                                                           0);
1342                                 if (!IS_ERR(key_ref))
1343                                         goto okay;
1344                         }
1345                 }
1346 
1347                 ret = PTR_ERR(key_ref);
1348                 goto error;
1349         }
1350 
1351 okay:
1352         key = key_ref_to_ptr(key_ref);
1353         ret = 0;
1354         if (test_bit(KEY_FLAG_KEEP, &key->flags))
1355                 ret = -EPERM;
1356         else
1357                 key_set_timeout(key, timeout);
1358         key_put(key);
1359 
1360 error:
1361         return ret;
1362 }
1363 
1364 /*
1365  * Assume (or clear) the authority to instantiate the specified key.
1366  *
1367  * This sets the authoritative token currently in force for key instantiation.
1368  * This must be done for a key to be instantiated.  It has the effect of making
1369  * available all the keys from the caller of the request_key() that created a
1370  * key to request_key() calls made by the caller of this function.
1371  *
1372  * The caller must have the instantiation key in their process keyrings with a
1373  * Search permission grant available to the caller.
1374  *
1375  * If the ID given is 0, then the setting will be cleared and 0 returned.
1376  *
1377  * If the ID given has a matching an authorisation key, then that key will be
1378  * set and its ID will be returned.  The authorisation key can be read to get
1379  * the callout information passed to request_key().
1380  */
1381 long keyctl_assume_authority(key_serial_t id)
1382 {
1383         struct key *authkey;
1384         long ret;
1385 
1386         /* special key IDs aren't permitted */
1387         ret = -EINVAL;
1388         if (id < 0)
1389                 goto error;
1390 
1391         /* we divest ourselves of authority if given an ID of 0 */
1392         if (id == 0) {
1393                 ret = keyctl_change_reqkey_auth(NULL);
1394                 goto error;
1395         }
1396 
1397         /* attempt to assume the authority temporarily granted to us whilst we
1398          * instantiate the specified key
1399          * - the authorisation key must be in the current task's keyrings
1400          *   somewhere
1401          */
1402         authkey = key_get_instantiation_authkey(id);
1403         if (IS_ERR(authkey)) {
1404                 ret = PTR_ERR(authkey);
1405                 goto error;
1406         }
1407 
1408         ret = keyctl_change_reqkey_auth(authkey);
1409         if (ret < 0)
1410                 goto error;
1411         key_put(authkey);
1412 
1413         ret = authkey->serial;
1414 error:
1415         return ret;
1416 }
1417 
1418 /*
1419  * Get a key's the LSM security label.
1420  *
1421  * The key must grant the caller View permission for this to work.
1422  *
1423  * If there's a buffer, then up to buflen bytes of data will be placed into it.
1424  *
1425  * If successful, the amount of information available will be returned,
1426  * irrespective of how much was copied (including the terminal NUL).
1427  */
1428 long keyctl_get_security(key_serial_t keyid,
1429                          char __user *buffer,
1430                          size_t buflen)
1431 {
1432         struct key *key, *instkey;
1433         key_ref_t key_ref;
1434         char *context;
1435         long ret;
1436 
1437         key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_VIEW);
1438         if (IS_ERR(key_ref)) {
1439                 if (PTR_ERR(key_ref) != -EACCES)
1440                         return PTR_ERR(key_ref);
1441 
1442                 /* viewing a key under construction is also permitted if we
1443                  * have the authorisation token handy */
1444                 instkey = key_get_instantiation_authkey(keyid);
1445                 if (IS_ERR(instkey))
1446                         return PTR_ERR(instkey);
1447                 key_put(instkey);
1448 
1449                 key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 0);
1450                 if (IS_ERR(key_ref))
1451                         return PTR_ERR(key_ref);
1452         }
1453 
1454         key = key_ref_to_ptr(key_ref);
1455         ret = security_key_getsecurity(key, &context);
1456         if (ret == 0) {
1457                 /* if no information was returned, give userspace an empty
1458                  * string */
1459                 ret = 1;
1460                 if (buffer && buflen > 0 &&
1461                     copy_to_user(buffer, "", 1) != 0)
1462                         ret = -EFAULT;
1463         } else if (ret > 0) {
1464                 /* return as much data as there's room for */
1465                 if (buffer && buflen > 0) {
1466                         if (buflen > ret)
1467                                 buflen = ret;
1468 
1469                         if (copy_to_user(buffer, context, buflen) != 0)
1470                                 ret = -EFAULT;
1471                 }
1472 
1473                 kfree(context);
1474         }
1475 
1476         key_ref_put(key_ref);
1477         return ret;
1478 }
1479 
1480 /*
1481  * Attempt to install the calling process's session keyring on the process's
1482  * parent process.
1483  *
1484  * The keyring must exist and must grant the caller LINK permission, and the
1485  * parent process must be single-threaded and must have the same effective
1486  * ownership as this process and mustn't be SUID/SGID.
1487  *
1488  * The keyring will be emplaced on the parent when it next resumes userspace.
1489  *
1490  * If successful, 0 will be returned.
1491  */
1492 long keyctl_session_to_parent(void)
1493 {
1494         struct task_struct *me, *parent;
1495         const struct cred *mycred, *pcred;
1496         struct callback_head *newwork, *oldwork;
1497         key_ref_t keyring_r;
1498         struct cred *cred;
1499         int ret;
1500 
1501         keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_NEED_LINK);
1502         if (IS_ERR(keyring_r))
1503                 return PTR_ERR(keyring_r);
1504 
1505         ret = -ENOMEM;
1506 
1507         /* our parent is going to need a new cred struct, a new tgcred struct
1508          * and new security data, so we allocate them here to prevent ENOMEM in
1509          * our parent */
1510         cred = cred_alloc_blank();
1511         if (!cred)
1512                 goto error_keyring;
1513         newwork = &cred->rcu;
1514 
1515         cred->session_keyring = key_ref_to_ptr(keyring_r);
1516         keyring_r = NULL;
1517         init_task_work(newwork, key_change_session_keyring);
1518 
1519         me = current;
1520         rcu_read_lock();
1521         write_lock_irq(&tasklist_lock);
1522 
1523         ret = -EPERM;
1524         oldwork = NULL;
1525         parent = me->real_parent;
1526 
1527         /* the parent mustn't be init and mustn't be a kernel thread */
1528         if (parent->pid <= 1 || !parent->mm)
1529                 goto unlock;
1530 
1531         /* the parent must be single threaded */
1532         if (!thread_group_empty(parent))
1533                 goto unlock;
1534 
1535         /* the parent and the child must have different session keyrings or
1536          * there's no point */
1537         mycred = current_cred();
1538         pcred = __task_cred(parent);
1539         if (mycred == pcred ||
1540             mycred->session_keyring == pcred->session_keyring) {
1541                 ret = 0;
1542                 goto unlock;
1543         }
1544 
1545         /* the parent must have the same effective ownership and mustn't be
1546          * SUID/SGID */
1547         if (!uid_eq(pcred->uid,  mycred->euid) ||
1548             !uid_eq(pcred->euid, mycred->euid) ||
1549             !uid_eq(pcred->suid, mycred->euid) ||
1550             !gid_eq(pcred->gid,  mycred->egid) ||
1551             !gid_eq(pcred->egid, mycred->egid) ||
1552             !gid_eq(pcred->sgid, mycred->egid))
1553                 goto unlock;
1554 
1555         /* the keyrings must have the same UID */
1556         if ((pcred->session_keyring &&
1557              !uid_eq(pcred->session_keyring->uid, mycred->euid)) ||
1558             !uid_eq(mycred->session_keyring->uid, mycred->euid))
1559                 goto unlock;
1560 
1561         /* cancel an already pending keyring replacement */
1562         oldwork = task_work_cancel(parent, key_change_session_keyring);
1563 
1564         /* the replacement session keyring is applied just prior to userspace
1565          * restarting */
1566         ret = task_work_add(parent, newwork, true);
1567         if (!ret)
1568                 newwork = NULL;
1569 unlock:
1570         write_unlock_irq(&tasklist_lock);
1571         rcu_read_unlock();
1572         if (oldwork)
1573                 put_cred(container_of(oldwork, struct cred, rcu));
1574         if (newwork)
1575                 put_cred(cred);
1576         return ret;
1577 
1578 error_keyring:
1579         key_ref_put(keyring_r);
1580         return ret;
1581 }
1582 
1583 /*
1584  * The key control system call
1585  */
1586 SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
1587                 unsigned long, arg4, unsigned long, arg5)
1588 {
1589         switch (option) {
1590         case KEYCTL_GET_KEYRING_ID:
1591                 return keyctl_get_keyring_ID((key_serial_t) arg2,
1592                                              (int) arg3);
1593 
1594         case KEYCTL_JOIN_SESSION_KEYRING:
1595                 return keyctl_join_session_keyring((const char __user *) arg2);
1596 
1597         case KEYCTL_UPDATE:
1598                 return keyctl_update_key((key_serial_t) arg2,
1599                                          (const void __user *) arg3,
1600                                          (size_t) arg4);
1601 
1602         case KEYCTL_REVOKE:
1603                 return keyctl_revoke_key((key_serial_t) arg2);
1604 
1605         case KEYCTL_DESCRIBE:
1606                 return keyctl_describe_key((key_serial_t) arg2,
1607                                            (char __user *) arg3,
1608                                            (unsigned) arg4);
1609 
1610         case KEYCTL_CLEAR:
1611                 return keyctl_keyring_clear((key_serial_t) arg2);
1612 
1613         case KEYCTL_LINK:
1614                 return keyctl_keyring_link((key_serial_t) arg2,
1615                                            (key_serial_t) arg3);
1616 
1617         case KEYCTL_UNLINK:
1618                 return keyctl_keyring_unlink((key_serial_t) arg2,
1619                                              (key_serial_t) arg3);
1620 
1621         case KEYCTL_SEARCH:
1622                 return keyctl_keyring_search((key_serial_t) arg2,
1623                                              (const char __user *) arg3,
1624                                              (const char __user *) arg4,
1625                                              (key_serial_t) arg5);
1626 
1627         case KEYCTL_READ:
1628                 return keyctl_read_key((key_serial_t) arg2,
1629                                        (char __user *) arg3,
1630                                        (size_t) arg4);
1631 
1632         case KEYCTL_CHOWN:
1633                 return keyctl_chown_key((key_serial_t) arg2,
1634                                         (uid_t) arg3,
1635                                         (gid_t) arg4);
1636 
1637         case KEYCTL_SETPERM:
1638                 return keyctl_setperm_key((key_serial_t) arg2,
1639                                           (key_perm_t) arg3);
1640 
1641         case KEYCTL_INSTANTIATE:
1642                 return keyctl_instantiate_key((key_serial_t) arg2,
1643                                               (const void __user *) arg3,
1644                                               (size_t) arg4,
1645                                               (key_serial_t) arg5);
1646 
1647         case KEYCTL_NEGATE:
1648                 return keyctl_negate_key((key_serial_t) arg2,
1649                                          (unsigned) arg3,
1650                                          (key_serial_t) arg4);
1651 
1652         case KEYCTL_SET_REQKEY_KEYRING:
1653                 return keyctl_set_reqkey_keyring(arg2);
1654 
1655         case KEYCTL_SET_TIMEOUT:
1656                 return keyctl_set_timeout((key_serial_t) arg2,
1657                                           (unsigned) arg3);
1658 
1659         case KEYCTL_ASSUME_AUTHORITY:
1660                 return keyctl_assume_authority((key_serial_t) arg2);
1661 
1662         case KEYCTL_GET_SECURITY:
1663                 return keyctl_get_security((key_serial_t) arg2,
1664                                            (char __user *) arg3,
1665                                            (size_t) arg4);
1666 
1667         case KEYCTL_SESSION_TO_PARENT:
1668                 return keyctl_session_to_parent();
1669 
1670         case KEYCTL_REJECT:
1671                 return keyctl_reject_key((key_serial_t) arg2,
1672                                          (unsigned) arg3,
1673                                          (unsigned) arg4,
1674                                          (key_serial_t) arg5);
1675 
1676         case KEYCTL_INSTANTIATE_IOV:
1677                 return keyctl_instantiate_key_iov(
1678                         (key_serial_t) arg2,
1679                         (const struct iovec __user *) arg3,
1680                         (unsigned) arg4,
1681                         (key_serial_t) arg5);
1682 
1683         case KEYCTL_INVALIDATE:
1684                 return keyctl_invalidate_key((key_serial_t) arg2);
1685 
1686         case KEYCTL_GET_PERSISTENT:
1687                 return keyctl_get_persistent((uid_t)arg2, (key_serial_t)arg3);
1688 
1689         default:
1690                 return -EOPNOTSUPP;
1691         }
1692 }
1693 

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