xref: /linux/security/keys/keyctl.c (revision 7d380c8f1ed2b6768e1fc496ad373f716160fcf0)
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 <asm/uaccess.h>
26 #include "internal.h"
27 
28 static int key_get_type_from_user(char *type,
29 				  const char __user *_type,
30 				  unsigned len)
31 {
32 	int ret;
33 
34 	ret = strncpy_from_user(type, _type, len);
35 	if (ret < 0)
36 		return ret;
37 	if (ret == 0 || ret >= len)
38 		return -EINVAL;
39 	if (type[0] == '.')
40 		return -EPERM;
41 	type[len - 1] = '\0';
42 	return 0;
43 }
44 
45 /*
46  * Extract the description of a new key from userspace and either add it as a
47  * new key to the specified keyring or update a matching key in that keyring.
48  *
49  * The keyring must be writable so that we can attach the key to it.
50  *
51  * If successful, the new key's serial number is returned, otherwise an error
52  * code is returned.
53  */
54 SYSCALL_DEFINE5(add_key, const char __user *, _type,
55 		const char __user *, _description,
56 		const void __user *, _payload,
57 		size_t, plen,
58 		key_serial_t, ringid)
59 {
60 	key_ref_t keyring_ref, key_ref;
61 	char type[32], *description;
62 	void *payload;
63 	long ret;
64 	bool vm;
65 
66 	ret = -EINVAL;
67 	if (plen > 1024 * 1024 - 1)
68 		goto error;
69 
70 	/* draw all the data into kernel space */
71 	ret = key_get_type_from_user(type, _type, sizeof(type));
72 	if (ret < 0)
73 		goto error;
74 
75 	description = strndup_user(_description, PAGE_SIZE);
76 	if (IS_ERR(description)) {
77 		ret = PTR_ERR(description);
78 		goto error;
79 	}
80 
81 	/* pull the payload in if one was supplied */
82 	payload = NULL;
83 
84 	vm = false;
85 	if (_payload) {
86 		ret = -ENOMEM;
87 		payload = kmalloc(plen, GFP_KERNEL | __GFP_NOWARN);
88 		if (!payload) {
89 			if (plen <= PAGE_SIZE)
90 				goto error2;
91 			vm = true;
92 			payload = vmalloc(plen);
93 			if (!payload)
94 				goto error2;
95 		}
96 
97 		ret = -EFAULT;
98 		if (copy_from_user(payload, _payload, plen) != 0)
99 			goto error3;
100 	}
101 
102 	/* find the target keyring (which must be writable) */
103 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
104 	if (IS_ERR(keyring_ref)) {
105 		ret = PTR_ERR(keyring_ref);
106 		goto error3;
107 	}
108 
109 	/* create or update the requested key and add it to the target
110 	 * keyring */
111 	key_ref = key_create_or_update(keyring_ref, type, description,
112 				       payload, plen, KEY_PERM_UNDEF,
113 				       KEY_ALLOC_IN_QUOTA);
114 	if (!IS_ERR(key_ref)) {
115 		ret = key_ref_to_ptr(key_ref)->serial;
116 		key_ref_put(key_ref);
117 	}
118 	else {
119 		ret = PTR_ERR(key_ref);
120 	}
121 
122 	key_ref_put(keyring_ref);
123  error3:
124 	if (!vm)
125 		kfree(payload);
126 	else
127 		vfree(payload);
128  error2:
129 	kfree(description);
130  error:
131 	return ret;
132 }
133 
134 /*
135  * Search the process keyrings and keyring trees linked from those for a
136  * matching key.  Keyrings must have appropriate Search permission to be
137  * searched.
138  *
139  * If a key is found, it will be attached to the destination keyring if there's
140  * one specified and the serial number of the key will be returned.
141  *
142  * If no key is found, /sbin/request-key will be invoked if _callout_info is
143  * non-NULL in an attempt to create a key.  The _callout_info string will be
144  * passed to /sbin/request-key to aid with completing the request.  If the
145  * _callout_info string is "" then it will be changed to "-".
146  */
147 SYSCALL_DEFINE4(request_key, const char __user *, _type,
148 		const char __user *, _description,
149 		const char __user *, _callout_info,
150 		key_serial_t, destringid)
151 {
152 	struct key_type *ktype;
153 	struct key *key;
154 	key_ref_t dest_ref;
155 	size_t callout_len;
156 	char type[32], *description, *callout_info;
157 	long ret;
158 
159 	/* pull the type into kernel space */
160 	ret = key_get_type_from_user(type, _type, sizeof(type));
161 	if (ret < 0)
162 		goto error;
163 
164 	/* pull the description into kernel space */
165 	description = strndup_user(_description, PAGE_SIZE);
166 	if (IS_ERR(description)) {
167 		ret = PTR_ERR(description);
168 		goto error;
169 	}
170 
171 	/* pull the callout info into kernel space */
172 	callout_info = NULL;
173 	callout_len = 0;
174 	if (_callout_info) {
175 		callout_info = strndup_user(_callout_info, PAGE_SIZE);
176 		if (IS_ERR(callout_info)) {
177 			ret = PTR_ERR(callout_info);
178 			goto error2;
179 		}
180 		callout_len = strlen(callout_info);
181 	}
182 
183 	/* get the destination keyring if specified */
184 	dest_ref = NULL;
185 	if (destringid) {
186 		dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
187 					   KEY_WRITE);
188 		if (IS_ERR(dest_ref)) {
189 			ret = PTR_ERR(dest_ref);
190 			goto error3;
191 		}
192 	}
193 
194 	/* find the key type */
195 	ktype = key_type_lookup(type);
196 	if (IS_ERR(ktype)) {
197 		ret = PTR_ERR(ktype);
198 		goto error4;
199 	}
200 
201 	/* do the search */
202 	key = request_key_and_link(ktype, description, callout_info,
203 				   callout_len, NULL, key_ref_to_ptr(dest_ref),
204 				   KEY_ALLOC_IN_QUOTA);
205 	if (IS_ERR(key)) {
206 		ret = PTR_ERR(key);
207 		goto error5;
208 	}
209 
210 	/* wait for the key to finish being constructed */
211 	ret = wait_for_key_construction(key, 1);
212 	if (ret < 0)
213 		goto error6;
214 
215 	ret = key->serial;
216 
217 error6:
218  	key_put(key);
219 error5:
220 	key_type_put(ktype);
221 error4:
222 	key_ref_put(dest_ref);
223 error3:
224 	kfree(callout_info);
225 error2:
226 	kfree(description);
227 error:
228 	return ret;
229 }
230 
231 /*
232  * Get the ID of the specified process keyring.
233  *
234  * The requested keyring must have search permission to be found.
235  *
236  * If successful, the ID of the requested keyring will be returned.
237  */
238 long keyctl_get_keyring_ID(key_serial_t id, int create)
239 {
240 	key_ref_t key_ref;
241 	unsigned long lflags;
242 	long ret;
243 
244 	lflags = create ? KEY_LOOKUP_CREATE : 0;
245 	key_ref = lookup_user_key(id, lflags, KEY_SEARCH);
246 	if (IS_ERR(key_ref)) {
247 		ret = PTR_ERR(key_ref);
248 		goto error;
249 	}
250 
251 	ret = key_ref_to_ptr(key_ref)->serial;
252 	key_ref_put(key_ref);
253 error:
254 	return ret;
255 }
256 
257 /*
258  * Join a (named) session keyring.
259  *
260  * Create and join an anonymous session keyring or join a named session
261  * keyring, creating it if necessary.  A named session keyring must have Search
262  * permission for it to be joined.  Session keyrings without this permit will
263  * be skipped over.
264  *
265  * If successful, the ID of the joined session keyring will be returned.
266  */
267 long keyctl_join_session_keyring(const char __user *_name)
268 {
269 	char *name;
270 	long ret;
271 
272 	/* fetch the name from userspace */
273 	name = NULL;
274 	if (_name) {
275 		name = strndup_user(_name, PAGE_SIZE);
276 		if (IS_ERR(name)) {
277 			ret = PTR_ERR(name);
278 			goto error;
279 		}
280 	}
281 
282 	/* join the session */
283 	ret = join_session_keyring(name);
284 	kfree(name);
285 
286 error:
287 	return ret;
288 }
289 
290 /*
291  * Update a key's data payload from the given data.
292  *
293  * The key must grant the caller Write permission and the key type must support
294  * updating for this to work.  A negative key can be positively instantiated
295  * with this call.
296  *
297  * If successful, 0 will be returned.  If the key type does not support
298  * updating, then -EOPNOTSUPP will be returned.
299  */
300 long keyctl_update_key(key_serial_t id,
301 		       const void __user *_payload,
302 		       size_t plen)
303 {
304 	key_ref_t key_ref;
305 	void *payload;
306 	long ret;
307 
308 	ret = -EINVAL;
309 	if (plen > PAGE_SIZE)
310 		goto error;
311 
312 	/* pull the payload in if one was supplied */
313 	payload = NULL;
314 	if (_payload) {
315 		ret = -ENOMEM;
316 		payload = kmalloc(plen, GFP_KERNEL);
317 		if (!payload)
318 			goto error;
319 
320 		ret = -EFAULT;
321 		if (copy_from_user(payload, _payload, plen) != 0)
322 			goto error2;
323 	}
324 
325 	/* find the target key (which must be writable) */
326 	key_ref = lookup_user_key(id, 0, KEY_WRITE);
327 	if (IS_ERR(key_ref)) {
328 		ret = PTR_ERR(key_ref);
329 		goto error2;
330 	}
331 
332 	/* update the key */
333 	ret = key_update(key_ref, payload, plen);
334 
335 	key_ref_put(key_ref);
336 error2:
337 	kfree(payload);
338 error:
339 	return ret;
340 }
341 
342 /*
343  * Revoke a key.
344  *
345  * The key must be grant the caller Write or Setattr permission for this to
346  * work.  The key type should give up its quota claim when revoked.  The key
347  * and any links to the key will be automatically garbage collected after a
348  * certain amount of time (/proc/sys/kernel/keys/gc_delay).
349  *
350  * If successful, 0 is returned.
351  */
352 long keyctl_revoke_key(key_serial_t id)
353 {
354 	key_ref_t key_ref;
355 	long ret;
356 
357 	key_ref = lookup_user_key(id, 0, KEY_WRITE);
358 	if (IS_ERR(key_ref)) {
359 		ret = PTR_ERR(key_ref);
360 		if (ret != -EACCES)
361 			goto error;
362 		key_ref = lookup_user_key(id, 0, KEY_SETATTR);
363 		if (IS_ERR(key_ref)) {
364 			ret = PTR_ERR(key_ref);
365 			goto error;
366 		}
367 	}
368 
369 	key_revoke(key_ref_to_ptr(key_ref));
370 	ret = 0;
371 
372 	key_ref_put(key_ref);
373 error:
374 	return ret;
375 }
376 
377 /*
378  * Invalidate a key.
379  *
380  * The key must be grant the caller Invalidate permission for this to work.
381  * The key and any links to the key will be automatically garbage collected
382  * immediately.
383  *
384  * If successful, 0 is returned.
385  */
386 long keyctl_invalidate_key(key_serial_t id)
387 {
388 	key_ref_t key_ref;
389 	long ret;
390 
391 	kenter("%d", id);
392 
393 	key_ref = lookup_user_key(id, 0, KEY_SEARCH);
394 	if (IS_ERR(key_ref)) {
395 		ret = PTR_ERR(key_ref);
396 		goto error;
397 	}
398 
399 	key_invalidate(key_ref_to_ptr(key_ref));
400 	ret = 0;
401 
402 	key_ref_put(key_ref);
403 error:
404 	kleave(" = %ld", ret);
405 	return ret;
406 }
407 
408 /*
409  * Clear the specified keyring, creating an empty process keyring if one of the
410  * special keyring IDs is used.
411  *
412  * The keyring must grant the caller Write permission for this to work.  If
413  * successful, 0 will be returned.
414  */
415 long keyctl_keyring_clear(key_serial_t ringid)
416 {
417 	key_ref_t keyring_ref;
418 	long ret;
419 
420 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
421 	if (IS_ERR(keyring_ref)) {
422 		ret = PTR_ERR(keyring_ref);
423 
424 		/* Root is permitted to invalidate certain special keyrings */
425 		if (capable(CAP_SYS_ADMIN)) {
426 			keyring_ref = lookup_user_key(ringid, 0, 0);
427 			if (IS_ERR(keyring_ref))
428 				goto error;
429 			if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
430 				     &key_ref_to_ptr(keyring_ref)->flags))
431 				goto clear;
432 			goto error_put;
433 		}
434 
435 		goto error;
436 	}
437 
438 clear:
439 	ret = keyring_clear(key_ref_to_ptr(keyring_ref));
440 error_put:
441 	key_ref_put(keyring_ref);
442 error:
443 	return ret;
444 }
445 
446 /*
447  * Create a link from a keyring to a key if there's no matching key in the
448  * keyring, otherwise replace the link to the matching key with a link to the
449  * new key.
450  *
451  * The key must grant the caller Link permission and the the keyring must grant
452  * the caller Write permission.  Furthermore, if an additional link is created,
453  * the keyring's quota will be extended.
454  *
455  * If successful, 0 will be returned.
456  */
457 long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
458 {
459 	key_ref_t keyring_ref, key_ref;
460 	long ret;
461 
462 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
463 	if (IS_ERR(keyring_ref)) {
464 		ret = PTR_ERR(keyring_ref);
465 		goto error;
466 	}
467 
468 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_LINK);
469 	if (IS_ERR(key_ref)) {
470 		ret = PTR_ERR(key_ref);
471 		goto error2;
472 	}
473 
474 	ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
475 
476 	key_ref_put(key_ref);
477 error2:
478 	key_ref_put(keyring_ref);
479 error:
480 	return ret;
481 }
482 
483 /*
484  * Unlink a key from a keyring.
485  *
486  * The keyring must grant the caller Write permission for this to work; the key
487  * itself need not grant the caller anything.  If the last link to a key is
488  * removed then that key will be scheduled for destruction.
489  *
490  * If successful, 0 will be returned.
491  */
492 long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
493 {
494 	key_ref_t keyring_ref, key_ref;
495 	long ret;
496 
497 	keyring_ref = lookup_user_key(ringid, 0, KEY_WRITE);
498 	if (IS_ERR(keyring_ref)) {
499 		ret = PTR_ERR(keyring_ref);
500 		goto error;
501 	}
502 
503 	key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 0);
504 	if (IS_ERR(key_ref)) {
505 		ret = PTR_ERR(key_ref);
506 		goto error2;
507 	}
508 
509 	ret = key_unlink(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
510 
511 	key_ref_put(key_ref);
512 error2:
513 	key_ref_put(keyring_ref);
514 error:
515 	return ret;
516 }
517 
518 /*
519  * Return a description of a key to userspace.
520  *
521  * The key must grant the caller View permission for this to work.
522  *
523  * If there's a buffer, we place up to buflen bytes of data into it formatted
524  * in the following way:
525  *
526  *	type;uid;gid;perm;description<NUL>
527  *
528  * If successful, we return the amount of description available, irrespective
529  * of how much we may have copied into the buffer.
530  */
531 long keyctl_describe_key(key_serial_t keyid,
532 			 char __user *buffer,
533 			 size_t buflen)
534 {
535 	struct key *key, *instkey;
536 	key_ref_t key_ref;
537 	char *tmpbuf;
538 	long ret;
539 
540 	key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);
541 	if (IS_ERR(key_ref)) {
542 		/* viewing a key under construction is permitted if we have the
543 		 * authorisation token handy */
544 		if (PTR_ERR(key_ref) == -EACCES) {
545 			instkey = key_get_instantiation_authkey(keyid);
546 			if (!IS_ERR(instkey)) {
547 				key_put(instkey);
548 				key_ref = lookup_user_key(keyid,
549 							  KEY_LOOKUP_PARTIAL,
550 							  0);
551 				if (!IS_ERR(key_ref))
552 					goto okay;
553 			}
554 		}
555 
556 		ret = PTR_ERR(key_ref);
557 		goto error;
558 	}
559 
560 okay:
561 	/* calculate how much description we're going to return */
562 	ret = -ENOMEM;
563 	tmpbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
564 	if (!tmpbuf)
565 		goto error2;
566 
567 	key = key_ref_to_ptr(key_ref);
568 
569 	ret = snprintf(tmpbuf, PAGE_SIZE - 1,
570 		       "%s;%d;%d;%08x;%s",
571 		       key->type->name,
572 		       from_kuid_munged(current_user_ns(), key->uid),
573 		       from_kgid_munged(current_user_ns(), key->gid),
574 		       key->perm,
575 		       key->description ?: "");
576 
577 	/* include a NUL char at the end of the data */
578 	if (ret > PAGE_SIZE - 1)
579 		ret = PAGE_SIZE - 1;
580 	tmpbuf[ret] = 0;
581 	ret++;
582 
583 	/* consider returning the data */
584 	if (buffer && buflen > 0) {
585 		if (buflen > ret)
586 			buflen = ret;
587 
588 		if (copy_to_user(buffer, tmpbuf, buflen) != 0)
589 			ret = -EFAULT;
590 	}
591 
592 	kfree(tmpbuf);
593 error2:
594 	key_ref_put(key_ref);
595 error:
596 	return ret;
597 }
598 
599 /*
600  * Search the specified keyring and any keyrings it links to for a matching
601  * key.  Only keyrings that grant the caller Search permission will be searched
602  * (this includes the starting keyring).  Only keys with Search permission can
603  * be found.
604  *
605  * If successful, the found key will be linked to the destination keyring if
606  * supplied and the key has Link permission, and the found key ID will be
607  * returned.
608  */
609 long keyctl_keyring_search(key_serial_t ringid,
610 			   const char __user *_type,
611 			   const char __user *_description,
612 			   key_serial_t destringid)
613 {
614 	struct key_type *ktype;
615 	key_ref_t keyring_ref, key_ref, dest_ref;
616 	char type[32], *description;
617 	long ret;
618 
619 	/* pull the type and description into kernel space */
620 	ret = key_get_type_from_user(type, _type, sizeof(type));
621 	if (ret < 0)
622 		goto error;
623 
624 	description = strndup_user(_description, PAGE_SIZE);
625 	if (IS_ERR(description)) {
626 		ret = PTR_ERR(description);
627 		goto error;
628 	}
629 
630 	/* get the keyring at which to begin the search */
631 	keyring_ref = lookup_user_key(ringid, 0, KEY_SEARCH);
632 	if (IS_ERR(keyring_ref)) {
633 		ret = PTR_ERR(keyring_ref);
634 		goto error2;
635 	}
636 
637 	/* get the destination keyring if specified */
638 	dest_ref = NULL;
639 	if (destringid) {
640 		dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
641 					   KEY_WRITE);
642 		if (IS_ERR(dest_ref)) {
643 			ret = PTR_ERR(dest_ref);
644 			goto error3;
645 		}
646 	}
647 
648 	/* find the key type */
649 	ktype = key_type_lookup(type);
650 	if (IS_ERR(ktype)) {
651 		ret = PTR_ERR(ktype);
652 		goto error4;
653 	}
654 
655 	/* do the search */
656 	key_ref = keyring_search(keyring_ref, ktype, description);
657 	if (IS_ERR(key_ref)) {
658 		ret = PTR_ERR(key_ref);
659 
660 		/* treat lack or presence of a negative key the same */
661 		if (ret == -EAGAIN)
662 			ret = -ENOKEY;
663 		goto error5;
664 	}
665 
666 	/* link the resulting key to the destination keyring if we can */
667 	if (dest_ref) {
668 		ret = key_permission(key_ref, KEY_LINK);
669 		if (ret < 0)
670 			goto error6;
671 
672 		ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
673 		if (ret < 0)
674 			goto error6;
675 	}
676 
677 	ret = key_ref_to_ptr(key_ref)->serial;
678 
679 error6:
680 	key_ref_put(key_ref);
681 error5:
682 	key_type_put(ktype);
683 error4:
684 	key_ref_put(dest_ref);
685 error3:
686 	key_ref_put(keyring_ref);
687 error2:
688 	kfree(description);
689 error:
690 	return ret;
691 }
692 
693 /*
694  * Read a key's payload.
695  *
696  * The key must either grant the caller Read permission, or it must grant the
697  * caller Search permission when searched for from the process keyrings.
698  *
699  * If successful, we place up to buflen bytes of data into the buffer, if one
700  * is provided, and return the amount of data that is available in the key,
701  * irrespective of how much we copied into the buffer.
702  */
703 long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
704 {
705 	struct key *key;
706 	key_ref_t key_ref;
707 	long ret;
708 
709 	/* find the key first */
710 	key_ref = lookup_user_key(keyid, 0, 0);
711 	if (IS_ERR(key_ref)) {
712 		ret = -ENOKEY;
713 		goto error;
714 	}
715 
716 	key = key_ref_to_ptr(key_ref);
717 
718 	/* see if we can read it directly */
719 	ret = key_permission(key_ref, KEY_READ);
720 	if (ret == 0)
721 		goto can_read_key;
722 	if (ret != -EACCES)
723 		goto error;
724 
725 	/* we can't; see if it's searchable from this process's keyrings
726 	 * - we automatically take account of the fact that it may be
727 	 *   dangling off an instantiation key
728 	 */
729 	if (!is_key_possessed(key_ref)) {
730 		ret = -EACCES;
731 		goto error2;
732 	}
733 
734 	/* the key is probably readable - now try to read it */
735 can_read_key:
736 	ret = key_validate(key);
737 	if (ret == 0) {
738 		ret = -EOPNOTSUPP;
739 		if (key->type->read) {
740 			/* read the data with the semaphore held (since we
741 			 * might sleep) */
742 			down_read(&key->sem);
743 			ret = key->type->read(key, buffer, buflen);
744 			up_read(&key->sem);
745 		}
746 	}
747 
748 error2:
749 	key_put(key);
750 error:
751 	return ret;
752 }
753 
754 /*
755  * Change the ownership of a key
756  *
757  * The key must grant the caller Setattr permission for this to work, though
758  * the key need not be fully instantiated yet.  For the UID to be changed, or
759  * for the GID to be changed to a group the caller is not a member of, the
760  * caller must have sysadmin capability.  If either uid or gid is -1 then that
761  * attribute is not changed.
762  *
763  * If the UID is to be changed, the new user must have sufficient quota to
764  * accept the key.  The quota deduction will be removed from the old user to
765  * the new user should the attribute be changed.
766  *
767  * If successful, 0 will be returned.
768  */
769 long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
770 {
771 	struct key_user *newowner, *zapowner = NULL;
772 	struct key *key;
773 	key_ref_t key_ref;
774 	long ret;
775 	kuid_t uid;
776 	kgid_t gid;
777 
778 	uid = make_kuid(current_user_ns(), user);
779 	gid = make_kgid(current_user_ns(), group);
780 	ret = -EINVAL;
781 	if ((user != (uid_t) -1) && !uid_valid(uid))
782 		goto error;
783 	if ((group != (gid_t) -1) && !gid_valid(gid))
784 		goto error;
785 
786 	ret = 0;
787 	if (user == (uid_t) -1 && group == (gid_t) -1)
788 		goto error;
789 
790 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
791 				  KEY_SETATTR);
792 	if (IS_ERR(key_ref)) {
793 		ret = PTR_ERR(key_ref);
794 		goto error;
795 	}
796 
797 	key = key_ref_to_ptr(key_ref);
798 
799 	/* make the changes with the locks held to prevent chown/chown races */
800 	ret = -EACCES;
801 	down_write(&key->sem);
802 
803 	if (!capable(CAP_SYS_ADMIN)) {
804 		/* only the sysadmin can chown a key to some other UID */
805 		if (user != (uid_t) -1 && !uid_eq(key->uid, uid))
806 			goto error_put;
807 
808 		/* only the sysadmin can set the key's GID to a group other
809 		 * than one of those that the current process subscribes to */
810 		if (group != (gid_t) -1 && !gid_eq(gid, key->gid) && !in_group_p(gid))
811 			goto error_put;
812 	}
813 
814 	/* change the UID */
815 	if (user != (uid_t) -1 && !uid_eq(uid, key->uid)) {
816 		ret = -ENOMEM;
817 		newowner = key_user_lookup(uid);
818 		if (!newowner)
819 			goto error_put;
820 
821 		/* transfer the quota burden to the new user */
822 		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
823 			unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
824 				key_quota_root_maxkeys : key_quota_maxkeys;
825 			unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
826 				key_quota_root_maxbytes : key_quota_maxbytes;
827 
828 			spin_lock(&newowner->lock);
829 			if (newowner->qnkeys + 1 >= maxkeys ||
830 			    newowner->qnbytes + key->quotalen >= maxbytes ||
831 			    newowner->qnbytes + key->quotalen <
832 			    newowner->qnbytes)
833 				goto quota_overrun;
834 
835 			newowner->qnkeys++;
836 			newowner->qnbytes += key->quotalen;
837 			spin_unlock(&newowner->lock);
838 
839 			spin_lock(&key->user->lock);
840 			key->user->qnkeys--;
841 			key->user->qnbytes -= key->quotalen;
842 			spin_unlock(&key->user->lock);
843 		}
844 
845 		atomic_dec(&key->user->nkeys);
846 		atomic_inc(&newowner->nkeys);
847 
848 		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
849 			atomic_dec(&key->user->nikeys);
850 			atomic_inc(&newowner->nikeys);
851 		}
852 
853 		zapowner = key->user;
854 		key->user = newowner;
855 		key->uid = uid;
856 	}
857 
858 	/* change the GID */
859 	if (group != (gid_t) -1)
860 		key->gid = gid;
861 
862 	ret = 0;
863 
864 error_put:
865 	up_write(&key->sem);
866 	key_put(key);
867 	if (zapowner)
868 		key_user_put(zapowner);
869 error:
870 	return ret;
871 
872 quota_overrun:
873 	spin_unlock(&newowner->lock);
874 	zapowner = newowner;
875 	ret = -EDQUOT;
876 	goto error_put;
877 }
878 
879 /*
880  * Change the permission mask on a key.
881  *
882  * The key must grant the caller Setattr permission for this to work, though
883  * the key need not be fully instantiated yet.  If the caller does not have
884  * sysadmin capability, it may only change the permission on keys that it owns.
885  */
886 long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
887 {
888 	struct key *key;
889 	key_ref_t key_ref;
890 	long ret;
891 
892 	ret = -EINVAL;
893 	if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
894 		goto error;
895 
896 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
897 				  KEY_SETATTR);
898 	if (IS_ERR(key_ref)) {
899 		ret = PTR_ERR(key_ref);
900 		goto error;
901 	}
902 
903 	key = key_ref_to_ptr(key_ref);
904 
905 	/* make the changes with the locks held to prevent chown/chmod races */
906 	ret = -EACCES;
907 	down_write(&key->sem);
908 
909 	/* if we're not the sysadmin, we can only change a key that we own */
910 	if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
911 		key->perm = perm;
912 		ret = 0;
913 	}
914 
915 	up_write(&key->sem);
916 	key_put(key);
917 error:
918 	return ret;
919 }
920 
921 /*
922  * Get the destination keyring for instantiation and check that the caller has
923  * Write permission on it.
924  */
925 static long get_instantiation_keyring(key_serial_t ringid,
926 				      struct request_key_auth *rka,
927 				      struct key **_dest_keyring)
928 {
929 	key_ref_t dkref;
930 
931 	*_dest_keyring = NULL;
932 
933 	/* just return a NULL pointer if we weren't asked to make a link */
934 	if (ringid == 0)
935 		return 0;
936 
937 	/* if a specific keyring is nominated by ID, then use that */
938 	if (ringid > 0) {
939 		dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
940 		if (IS_ERR(dkref))
941 			return PTR_ERR(dkref);
942 		*_dest_keyring = key_ref_to_ptr(dkref);
943 		return 0;
944 	}
945 
946 	if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
947 		return -EINVAL;
948 
949 	/* otherwise specify the destination keyring recorded in the
950 	 * authorisation key (any KEY_SPEC_*_KEYRING) */
951 	if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
952 		*_dest_keyring = key_get(rka->dest_keyring);
953 		return 0;
954 	}
955 
956 	return -ENOKEY;
957 }
958 
959 /*
960  * Change the request_key authorisation key on the current process.
961  */
962 static int keyctl_change_reqkey_auth(struct key *key)
963 {
964 	struct cred *new;
965 
966 	new = prepare_creds();
967 	if (!new)
968 		return -ENOMEM;
969 
970 	key_put(new->request_key_auth);
971 	new->request_key_auth = key_get(key);
972 
973 	return commit_creds(new);
974 }
975 
976 /*
977  * Copy the iovec data from userspace
978  */
979 static long copy_from_user_iovec(void *buffer, const struct iovec *iov,
980 				 unsigned ioc)
981 {
982 	for (; ioc > 0; ioc--) {
983 		if (copy_from_user(buffer, iov->iov_base, iov->iov_len) != 0)
984 			return -EFAULT;
985 		buffer += iov->iov_len;
986 		iov++;
987 	}
988 	return 0;
989 }
990 
991 /*
992  * Instantiate a key with the specified payload and link the key into the
993  * destination keyring if one is given.
994  *
995  * The caller must have the appropriate instantiation permit set for this to
996  * work (see keyctl_assume_authority).  No other permissions are required.
997  *
998  * If successful, 0 will be returned.
999  */
1000 long keyctl_instantiate_key_common(key_serial_t id,
1001 				   const struct iovec *payload_iov,
1002 				   unsigned ioc,
1003 				   size_t plen,
1004 				   key_serial_t ringid)
1005 {
1006 	const struct cred *cred = current_cred();
1007 	struct request_key_auth *rka;
1008 	struct key *instkey, *dest_keyring;
1009 	void *payload;
1010 	long ret;
1011 	bool vm = false;
1012 
1013 	kenter("%d,,%zu,%d", id, plen, ringid);
1014 
1015 	ret = -EINVAL;
1016 	if (plen > 1024 * 1024 - 1)
1017 		goto error;
1018 
1019 	/* the appropriate instantiation authorisation key must have been
1020 	 * assumed before calling this */
1021 	ret = -EPERM;
1022 	instkey = cred->request_key_auth;
1023 	if (!instkey)
1024 		goto error;
1025 
1026 	rka = instkey->payload.data;
1027 	if (rka->target_key->serial != id)
1028 		goto error;
1029 
1030 	/* pull the payload in if one was supplied */
1031 	payload = NULL;
1032 
1033 	if (payload_iov) {
1034 		ret = -ENOMEM;
1035 		payload = kmalloc(plen, GFP_KERNEL);
1036 		if (!payload) {
1037 			if (plen <= PAGE_SIZE)
1038 				goto error;
1039 			vm = true;
1040 			payload = vmalloc(plen);
1041 			if (!payload)
1042 				goto error;
1043 		}
1044 
1045 		ret = copy_from_user_iovec(payload, payload_iov, ioc);
1046 		if (ret < 0)
1047 			goto error2;
1048 	}
1049 
1050 	/* find the destination keyring amongst those belonging to the
1051 	 * requesting task */
1052 	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1053 	if (ret < 0)
1054 		goto error2;
1055 
1056 	/* instantiate the key and link it into a keyring */
1057 	ret = key_instantiate_and_link(rka->target_key, payload, plen,
1058 				       dest_keyring, instkey);
1059 
1060 	key_put(dest_keyring);
1061 
1062 	/* discard the assumed authority if it's just been disabled by
1063 	 * instantiation of the key */
1064 	if (ret == 0)
1065 		keyctl_change_reqkey_auth(NULL);
1066 
1067 error2:
1068 	if (!vm)
1069 		kfree(payload);
1070 	else
1071 		vfree(payload);
1072 error:
1073 	return ret;
1074 }
1075 
1076 /*
1077  * Instantiate a key with the specified payload and link the key into the
1078  * destination keyring if one is given.
1079  *
1080  * The caller must have the appropriate instantiation permit set for this to
1081  * work (see keyctl_assume_authority).  No other permissions are required.
1082  *
1083  * If successful, 0 will be returned.
1084  */
1085 long keyctl_instantiate_key(key_serial_t id,
1086 			    const void __user *_payload,
1087 			    size_t plen,
1088 			    key_serial_t ringid)
1089 {
1090 	if (_payload && plen) {
1091 		struct iovec iov[1] = {
1092 			[0].iov_base = (void __user *)_payload,
1093 			[0].iov_len  = plen
1094 		};
1095 
1096 		return keyctl_instantiate_key_common(id, iov, 1, plen, ringid);
1097 	}
1098 
1099 	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
1100 }
1101 
1102 /*
1103  * Instantiate a key with the specified multipart payload and link the key into
1104  * the destination keyring if one is given.
1105  *
1106  * The caller must have the appropriate instantiation permit set for this to
1107  * work (see keyctl_assume_authority).  No other permissions are required.
1108  *
1109  * If successful, 0 will be returned.
1110  */
1111 long keyctl_instantiate_key_iov(key_serial_t id,
1112 				const struct iovec __user *_payload_iov,
1113 				unsigned ioc,
1114 				key_serial_t ringid)
1115 {
1116 	struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
1117 	long ret;
1118 
1119 	if (!_payload_iov || !ioc)
1120 		goto no_payload;
1121 
1122 	ret = rw_copy_check_uvector(WRITE, _payload_iov, ioc,
1123 				    ARRAY_SIZE(iovstack), iovstack, &iov);
1124 	if (ret < 0)
1125 		return ret;
1126 	if (ret == 0)
1127 		goto no_payload_free;
1128 
1129 	ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);
1130 
1131 	if (iov != iovstack)
1132 		kfree(iov);
1133 	return ret;
1134 
1135 no_payload_free:
1136 	if (iov != iovstack)
1137 		kfree(iov);
1138 no_payload:
1139 	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
1140 }
1141 
1142 /*
1143  * Negatively instantiate the key with the given timeout (in seconds) and link
1144  * the key into the destination keyring if one is given.
1145  *
1146  * The caller must have the appropriate instantiation permit set for this to
1147  * work (see keyctl_assume_authority).  No other permissions are required.
1148  *
1149  * The key and any links to the key will be automatically garbage collected
1150  * after the timeout expires.
1151  *
1152  * Negative keys are used to rate limit repeated request_key() calls by causing
1153  * them to return -ENOKEY until the negative key expires.
1154  *
1155  * If successful, 0 will be returned.
1156  */
1157 long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
1158 {
1159 	return keyctl_reject_key(id, timeout, ENOKEY, ringid);
1160 }
1161 
1162 /*
1163  * Negatively instantiate the key with the given timeout (in seconds) and error
1164  * code and link the key into the destination keyring if one is given.
1165  *
1166  * The caller must have the appropriate instantiation permit set for this to
1167  * work (see keyctl_assume_authority).  No other permissions are required.
1168  *
1169  * The key and any links to the key will be automatically garbage collected
1170  * after the timeout expires.
1171  *
1172  * Negative keys are used to rate limit repeated request_key() calls by causing
1173  * them to return the specified error code until the negative key expires.
1174  *
1175  * If successful, 0 will be returned.
1176  */
1177 long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
1178 		       key_serial_t ringid)
1179 {
1180 	const struct cred *cred = current_cred();
1181 	struct request_key_auth *rka;
1182 	struct key *instkey, *dest_keyring;
1183 	long ret;
1184 
1185 	kenter("%d,%u,%u,%d", id, timeout, error, ringid);
1186 
1187 	/* must be a valid error code and mustn't be a kernel special */
1188 	if (error <= 0 ||
1189 	    error >= MAX_ERRNO ||
1190 	    error == ERESTARTSYS ||
1191 	    error == ERESTARTNOINTR ||
1192 	    error == ERESTARTNOHAND ||
1193 	    error == ERESTART_RESTARTBLOCK)
1194 		return -EINVAL;
1195 
1196 	/* the appropriate instantiation authorisation key must have been
1197 	 * assumed before calling this */
1198 	ret = -EPERM;
1199 	instkey = cred->request_key_auth;
1200 	if (!instkey)
1201 		goto error;
1202 
1203 	rka = instkey->payload.data;
1204 	if (rka->target_key->serial != id)
1205 		goto error;
1206 
1207 	/* find the destination keyring if present (which must also be
1208 	 * writable) */
1209 	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1210 	if (ret < 0)
1211 		goto error;
1212 
1213 	/* instantiate the key and link it into a keyring */
1214 	ret = key_reject_and_link(rka->target_key, timeout, error,
1215 				  dest_keyring, instkey);
1216 
1217 	key_put(dest_keyring);
1218 
1219 	/* discard the assumed authority if it's just been disabled by
1220 	 * instantiation of the key */
1221 	if (ret == 0)
1222 		keyctl_change_reqkey_auth(NULL);
1223 
1224 error:
1225 	return ret;
1226 }
1227 
1228 /*
1229  * Read or set the default keyring in which request_key() will cache keys and
1230  * return the old setting.
1231  *
1232  * If a process keyring is specified then this will be created if it doesn't
1233  * yet exist.  The old setting will be returned if successful.
1234  */
1235 long keyctl_set_reqkey_keyring(int reqkey_defl)
1236 {
1237 	struct cred *new;
1238 	int ret, old_setting;
1239 
1240 	old_setting = current_cred_xxx(jit_keyring);
1241 
1242 	if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
1243 		return old_setting;
1244 
1245 	new = prepare_creds();
1246 	if (!new)
1247 		return -ENOMEM;
1248 
1249 	switch (reqkey_defl) {
1250 	case KEY_REQKEY_DEFL_THREAD_KEYRING:
1251 		ret = install_thread_keyring_to_cred(new);
1252 		if (ret < 0)
1253 			goto error;
1254 		goto set;
1255 
1256 	case KEY_REQKEY_DEFL_PROCESS_KEYRING:
1257 		ret = install_process_keyring_to_cred(new);
1258 		if (ret < 0) {
1259 			if (ret != -EEXIST)
1260 				goto error;
1261 			ret = 0;
1262 		}
1263 		goto set;
1264 
1265 	case KEY_REQKEY_DEFL_DEFAULT:
1266 	case KEY_REQKEY_DEFL_SESSION_KEYRING:
1267 	case KEY_REQKEY_DEFL_USER_KEYRING:
1268 	case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
1269 	case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
1270 		goto set;
1271 
1272 	case KEY_REQKEY_DEFL_NO_CHANGE:
1273 	case KEY_REQKEY_DEFL_GROUP_KEYRING:
1274 	default:
1275 		ret = -EINVAL;
1276 		goto error;
1277 	}
1278 
1279 set:
1280 	new->jit_keyring = reqkey_defl;
1281 	commit_creds(new);
1282 	return old_setting;
1283 error:
1284 	abort_creds(new);
1285 	return ret;
1286 }
1287 
1288 /*
1289  * Set or clear the timeout on a key.
1290  *
1291  * Either the key must grant the caller Setattr permission or else the caller
1292  * must hold an instantiation authorisation token for the key.
1293  *
1294  * The timeout is either 0 to clear the timeout, or a number of seconds from
1295  * the current time.  The key and any links to the key will be automatically
1296  * garbage collected after the timeout expires.
1297  *
1298  * If successful, 0 is returned.
1299  */
1300 long keyctl_set_timeout(key_serial_t id, unsigned timeout)
1301 {
1302 	struct key *key, *instkey;
1303 	key_ref_t key_ref;
1304 	long ret;
1305 
1306 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
1307 				  KEY_SETATTR);
1308 	if (IS_ERR(key_ref)) {
1309 		/* setting the timeout on a key under construction is permitted
1310 		 * if we have the authorisation token handy */
1311 		if (PTR_ERR(key_ref) == -EACCES) {
1312 			instkey = key_get_instantiation_authkey(id);
1313 			if (!IS_ERR(instkey)) {
1314 				key_put(instkey);
1315 				key_ref = lookup_user_key(id,
1316 							  KEY_LOOKUP_PARTIAL,
1317 							  0);
1318 				if (!IS_ERR(key_ref))
1319 					goto okay;
1320 			}
1321 		}
1322 
1323 		ret = PTR_ERR(key_ref);
1324 		goto error;
1325 	}
1326 
1327 okay:
1328 	key = key_ref_to_ptr(key_ref);
1329 	key_set_timeout(key, timeout);
1330 	key_put(key);
1331 
1332 	ret = 0;
1333 error:
1334 	return ret;
1335 }
1336 
1337 /*
1338  * Assume (or clear) the authority to instantiate the specified key.
1339  *
1340  * This sets the authoritative token currently in force for key instantiation.
1341  * This must be done for a key to be instantiated.  It has the effect of making
1342  * available all the keys from the caller of the request_key() that created a
1343  * key to request_key() calls made by the caller of this function.
1344  *
1345  * The caller must have the instantiation key in their process keyrings with a
1346  * Search permission grant available to the caller.
1347  *
1348  * If the ID given is 0, then the setting will be cleared and 0 returned.
1349  *
1350  * If the ID given has a matching an authorisation key, then that key will be
1351  * set and its ID will be returned.  The authorisation key can be read to get
1352  * the callout information passed to request_key().
1353  */
1354 long keyctl_assume_authority(key_serial_t id)
1355 {
1356 	struct key *authkey;
1357 	long ret;
1358 
1359 	/* special key IDs aren't permitted */
1360 	ret = -EINVAL;
1361 	if (id < 0)
1362 		goto error;
1363 
1364 	/* we divest ourselves of authority if given an ID of 0 */
1365 	if (id == 0) {
1366 		ret = keyctl_change_reqkey_auth(NULL);
1367 		goto error;
1368 	}
1369 
1370 	/* attempt to assume the authority temporarily granted to us whilst we
1371 	 * instantiate the specified key
1372 	 * - the authorisation key must be in the current task's keyrings
1373 	 *   somewhere
1374 	 */
1375 	authkey = key_get_instantiation_authkey(id);
1376 	if (IS_ERR(authkey)) {
1377 		ret = PTR_ERR(authkey);
1378 		goto error;
1379 	}
1380 
1381 	ret = keyctl_change_reqkey_auth(authkey);
1382 	if (ret < 0)
1383 		goto error;
1384 	key_put(authkey);
1385 
1386 	ret = authkey->serial;
1387 error:
1388 	return ret;
1389 }
1390 
1391 /*
1392  * Get a key's the LSM security label.
1393  *
1394  * The key must grant the caller View permission for this to work.
1395  *
1396  * If there's a buffer, then up to buflen bytes of data will be placed into it.
1397  *
1398  * If successful, the amount of information available will be returned,
1399  * irrespective of how much was copied (including the terminal NUL).
1400  */
1401 long keyctl_get_security(key_serial_t keyid,
1402 			 char __user *buffer,
1403 			 size_t buflen)
1404 {
1405 	struct key *key, *instkey;
1406 	key_ref_t key_ref;
1407 	char *context;
1408 	long ret;
1409 
1410 	key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);
1411 	if (IS_ERR(key_ref)) {
1412 		if (PTR_ERR(key_ref) != -EACCES)
1413 			return PTR_ERR(key_ref);
1414 
1415 		/* viewing a key under construction is also permitted if we
1416 		 * have the authorisation token handy */
1417 		instkey = key_get_instantiation_authkey(keyid);
1418 		if (IS_ERR(instkey))
1419 			return PTR_ERR(instkey);
1420 		key_put(instkey);
1421 
1422 		key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 0);
1423 		if (IS_ERR(key_ref))
1424 			return PTR_ERR(key_ref);
1425 	}
1426 
1427 	key = key_ref_to_ptr(key_ref);
1428 	ret = security_key_getsecurity(key, &context);
1429 	if (ret == 0) {
1430 		/* if no information was returned, give userspace an empty
1431 		 * string */
1432 		ret = 1;
1433 		if (buffer && buflen > 0 &&
1434 		    copy_to_user(buffer, "", 1) != 0)
1435 			ret = -EFAULT;
1436 	} else if (ret > 0) {
1437 		/* return as much data as there's room for */
1438 		if (buffer && buflen > 0) {
1439 			if (buflen > ret)
1440 				buflen = ret;
1441 
1442 			if (copy_to_user(buffer, context, buflen) != 0)
1443 				ret = -EFAULT;
1444 		}
1445 
1446 		kfree(context);
1447 	}
1448 
1449 	key_ref_put(key_ref);
1450 	return ret;
1451 }
1452 
1453 /*
1454  * Attempt to install the calling process's session keyring on the process's
1455  * parent process.
1456  *
1457  * The keyring must exist and must grant the caller LINK permission, and the
1458  * parent process must be single-threaded and must have the same effective
1459  * ownership as this process and mustn't be SUID/SGID.
1460  *
1461  * The keyring will be emplaced on the parent when it next resumes userspace.
1462  *
1463  * If successful, 0 will be returned.
1464  */
1465 long keyctl_session_to_parent(void)
1466 {
1467 	struct task_struct *me, *parent;
1468 	const struct cred *mycred, *pcred;
1469 	struct callback_head *newwork, *oldwork;
1470 	key_ref_t keyring_r;
1471 	struct cred *cred;
1472 	int ret;
1473 
1474 	keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
1475 	if (IS_ERR(keyring_r))
1476 		return PTR_ERR(keyring_r);
1477 
1478 	ret = -ENOMEM;
1479 
1480 	/* our parent is going to need a new cred struct, a new tgcred struct
1481 	 * and new security data, so we allocate them here to prevent ENOMEM in
1482 	 * our parent */
1483 	cred = cred_alloc_blank();
1484 	if (!cred)
1485 		goto error_keyring;
1486 	newwork = &cred->rcu;
1487 
1488 	cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
1489 	init_task_work(newwork, key_change_session_keyring);
1490 
1491 	me = current;
1492 	rcu_read_lock();
1493 	write_lock_irq(&tasklist_lock);
1494 
1495 	ret = -EPERM;
1496 	oldwork = NULL;
1497 	parent = me->real_parent;
1498 
1499 	/* the parent mustn't be init and mustn't be a kernel thread */
1500 	if (parent->pid <= 1 || !parent->mm)
1501 		goto unlock;
1502 
1503 	/* the parent must be single threaded */
1504 	if (!thread_group_empty(parent))
1505 		goto unlock;
1506 
1507 	/* the parent and the child must have different session keyrings or
1508 	 * there's no point */
1509 	mycred = current_cred();
1510 	pcred = __task_cred(parent);
1511 	if (mycred == pcred ||
1512 	    mycred->tgcred->session_keyring == pcred->tgcred->session_keyring) {
1513 		ret = 0;
1514 		goto unlock;
1515 	}
1516 
1517 	/* the parent must have the same effective ownership and mustn't be
1518 	 * SUID/SGID */
1519 	if (!uid_eq(pcred->uid,	 mycred->euid) ||
1520 	    !uid_eq(pcred->euid, mycred->euid) ||
1521 	    !uid_eq(pcred->suid, mycred->euid) ||
1522 	    !gid_eq(pcred->gid,	 mycred->egid) ||
1523 	    !gid_eq(pcred->egid, mycred->egid) ||
1524 	    !gid_eq(pcred->sgid, mycred->egid))
1525 		goto unlock;
1526 
1527 	/* the keyrings must have the same UID */
1528 	if ((pcred->tgcred->session_keyring &&
1529 	     !uid_eq(pcred->tgcred->session_keyring->uid, mycred->euid)) ||
1530 	    !uid_eq(mycred->tgcred->session_keyring->uid, mycred->euid))
1531 		goto unlock;
1532 
1533 	/* cancel an already pending keyring replacement */
1534 	oldwork = task_work_cancel(parent, key_change_session_keyring);
1535 
1536 	/* the replacement session keyring is applied just prior to userspace
1537 	 * restarting */
1538 	ret = task_work_add(parent, newwork, true);
1539 	if (!ret)
1540 		newwork = NULL;
1541 unlock:
1542 	write_unlock_irq(&tasklist_lock);
1543 	rcu_read_unlock();
1544 	if (oldwork)
1545 		put_cred(container_of(oldwork, struct cred, rcu));
1546 	if (newwork)
1547 		put_cred(cred);
1548 	return ret;
1549 
1550 error_keyring:
1551 	key_ref_put(keyring_r);
1552 	return ret;
1553 }
1554 
1555 /*
1556  * The key control system call
1557  */
1558 SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
1559 		unsigned long, arg4, unsigned long, arg5)
1560 {
1561 	switch (option) {
1562 	case KEYCTL_GET_KEYRING_ID:
1563 		return keyctl_get_keyring_ID((key_serial_t) arg2,
1564 					     (int) arg3);
1565 
1566 	case KEYCTL_JOIN_SESSION_KEYRING:
1567 		return keyctl_join_session_keyring((const char __user *) arg2);
1568 
1569 	case KEYCTL_UPDATE:
1570 		return keyctl_update_key((key_serial_t) arg2,
1571 					 (const void __user *) arg3,
1572 					 (size_t) arg4);
1573 
1574 	case KEYCTL_REVOKE:
1575 		return keyctl_revoke_key((key_serial_t) arg2);
1576 
1577 	case KEYCTL_DESCRIBE:
1578 		return keyctl_describe_key((key_serial_t) arg2,
1579 					   (char __user *) arg3,
1580 					   (unsigned) arg4);
1581 
1582 	case KEYCTL_CLEAR:
1583 		return keyctl_keyring_clear((key_serial_t) arg2);
1584 
1585 	case KEYCTL_LINK:
1586 		return keyctl_keyring_link((key_serial_t) arg2,
1587 					   (key_serial_t) arg3);
1588 
1589 	case KEYCTL_UNLINK:
1590 		return keyctl_keyring_unlink((key_serial_t) arg2,
1591 					     (key_serial_t) arg3);
1592 
1593 	case KEYCTL_SEARCH:
1594 		return keyctl_keyring_search((key_serial_t) arg2,
1595 					     (const char __user *) arg3,
1596 					     (const char __user *) arg4,
1597 					     (key_serial_t) arg5);
1598 
1599 	case KEYCTL_READ:
1600 		return keyctl_read_key((key_serial_t) arg2,
1601 				       (char __user *) arg3,
1602 				       (size_t) arg4);
1603 
1604 	case KEYCTL_CHOWN:
1605 		return keyctl_chown_key((key_serial_t) arg2,
1606 					(uid_t) arg3,
1607 					(gid_t) arg4);
1608 
1609 	case KEYCTL_SETPERM:
1610 		return keyctl_setperm_key((key_serial_t) arg2,
1611 					  (key_perm_t) arg3);
1612 
1613 	case KEYCTL_INSTANTIATE:
1614 		return keyctl_instantiate_key((key_serial_t) arg2,
1615 					      (const void __user *) arg3,
1616 					      (size_t) arg4,
1617 					      (key_serial_t) arg5);
1618 
1619 	case KEYCTL_NEGATE:
1620 		return keyctl_negate_key((key_serial_t) arg2,
1621 					 (unsigned) arg3,
1622 					 (key_serial_t) arg4);
1623 
1624 	case KEYCTL_SET_REQKEY_KEYRING:
1625 		return keyctl_set_reqkey_keyring(arg2);
1626 
1627 	case KEYCTL_SET_TIMEOUT:
1628 		return keyctl_set_timeout((key_serial_t) arg2,
1629 					  (unsigned) arg3);
1630 
1631 	case KEYCTL_ASSUME_AUTHORITY:
1632 		return keyctl_assume_authority((key_serial_t) arg2);
1633 
1634 	case KEYCTL_GET_SECURITY:
1635 		return keyctl_get_security((key_serial_t) arg2,
1636 					   (char __user *) arg3,
1637 					   (size_t) arg4);
1638 
1639 	case KEYCTL_SESSION_TO_PARENT:
1640 		return keyctl_session_to_parent();
1641 
1642 	case KEYCTL_REJECT:
1643 		return keyctl_reject_key((key_serial_t) arg2,
1644 					 (unsigned) arg3,
1645 					 (unsigned) arg4,
1646 					 (key_serial_t) arg5);
1647 
1648 	case KEYCTL_INSTANTIATE_IOV:
1649 		return keyctl_instantiate_key_iov(
1650 			(key_serial_t) arg2,
1651 			(const struct iovec __user *) arg3,
1652 			(unsigned) arg4,
1653 			(key_serial_t) arg5);
1654 
1655 	case KEYCTL_INVALIDATE:
1656 		return keyctl_invalidate_key((key_serial_t) arg2);
1657 
1658 	default:
1659 		return -EOPNOTSUPP;
1660 	}
1661 }
1662