1/*-
2 * Copyright (c) 1999-2002, 2006, 2009 Robert N. M. Watson
3 * Copyright (c) 2001 Ilmar S. Habibulin
4 * Copyright (c) 2001-2005 Networks Associates Technology, Inc.
5 * Copyright (c) 2005-2006 SPARTA, Inc.
6 * Copyright (c) 2008-2009 Apple Inc.
7 * All rights reserved.
8 *
9 * This software was developed by Robert Watson and Ilmar Habibulin for the
10 * TrustedBSD Project.
11 *
12 * This software was developed for the FreeBSD Project in part by Network
13 * Associates Laboratories, the Security Research Division of Network
14 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
15 * as part of the DARPA CHATS research program.
16 *
17 * This software was enhanced by SPARTA ISSO under SPAWAR contract
18 * N66001-04-C-6019 ("SEFOS").
19 *
20 * This software was developed at the University of Cambridge Computer
21 * Laboratory with support from a grant from Google, Inc.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the above copyright
27 *    notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 *    notice, this list of conditions and the following disclaimer in the
30 *    documentation and/or other materials provided with the distribution.
31 *
32 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
33 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
34 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
35 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
36 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
37 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
38 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
40 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
41 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
42 * SUCH DAMAGE.
43 */
44
45/*-
46 * Framework for extensible kernel access control.  This file contains core
47 * kernel infrastructure for the TrustedBSD MAC Framework, including policy
48 * registration, versioning, locking, error composition operator, and system
49 * calls.
50 *
51 * The MAC Framework implements three programming interfaces:
52 *
53 * - The kernel MAC interface, defined in mac_framework.h, and invoked
54 *   throughout the kernel to request security decisions, notify of security
55 *   related events, etc.
56 *
57 * - The MAC policy module interface, defined in mac_policy.h, which is
58 *   implemented by MAC policy modules and invoked by the MAC Framework to
59 *   forward kernel security requests and notifications to policy modules.
60 *
61 * - The user MAC API, defined in mac.h, which allows user programs to query
62 *   and set label state on objects.
63 *
64 * The majority of the MAC Framework implementation may be found in
65 * src/sys/security/mac.  Sample policy modules may be found in
66 * src/sys/security/mac_*.
67 */
68
69#include "opt_mac.h"
70
71#include <sys/cdefs.h>
72__FBSDID("$FreeBSD$");
73
74#include <sys/param.h>
75#include <sys/systm.h>
76#include <sys/condvar.h>
77#include <sys/kernel.h>
78#include <sys/lock.h>
79#include <sys/mac.h>
80#include <sys/module.h>
81#include <sys/rmlock.h>
82#include <sys/sdt.h>
83#include <sys/sx.h>
84#include <sys/sysctl.h>
85#include <sys/vnode.h>
86
87#include <security/mac/mac_framework.h>
88#include <security/mac/mac_internal.h>
89#include <security/mac/mac_policy.h>
90
91/*
92 * DTrace SDT providers for MAC.
93 */
94SDT_PROVIDER_DEFINE(mac);
95SDT_PROVIDER_DEFINE(mac_framework);
96
97SDT_PROBE_DEFINE2(mac, , policy, modevent, "int",
98    "struct mac_policy_conf *");
99SDT_PROBE_DEFINE1(mac, , policy, register,
100    "struct mac_policy_conf *");
101SDT_PROBE_DEFINE1(mac, , policy, unregister,
102    "struct mac_policy_conf *");
103
104/*
105 * Root sysctl node for all MAC and MAC policy controls.
106 */
107SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
108    "TrustedBSD MAC policy controls");
109
110/*
111 * Declare that the kernel provides MAC support, version 3 (FreeBSD 7.x).
112 * This permits modules to refuse to be loaded if the necessary support isn't
113 * present, even if it's pre-boot.
114 */
115MODULE_VERSION(kernel_mac_support, MAC_VERSION);
116
117static unsigned int	mac_version = MAC_VERSION;
118SYSCTL_UINT(_security_mac, OID_AUTO, version, CTLFLAG_RD, &mac_version, 0,
119    "");
120
121/*
122 * Flags for inlined checks. Note this would be best hotpatched at runtime.
123 * The following is a band-aid.
124 *
125 * Use FPFLAG for hooks running in commonly executed paths and FPFLAG_RARE
126 * for the rest.
127 */
128#define FPFLAG(f)	\
129bool __read_frequently mac_##f##_fp_flag
130
131#define FPFLAG_RARE(f)	\
132bool __read_mostly mac_##f##_fp_flag
133
134FPFLAG(priv_check);
135FPFLAG(priv_grant);
136FPFLAG(vnode_check_lookup);
137FPFLAG(vnode_check_open);
138FPFLAG(vnode_check_stat);
139FPFLAG(vnode_check_read);
140FPFLAG(vnode_check_write);
141FPFLAG(vnode_check_mmap);
142FPFLAG_RARE(vnode_check_poll);
143FPFLAG_RARE(vnode_check_rename_from);
144FPFLAG_RARE(vnode_check_access);
145FPFLAG_RARE(vnode_check_readlink);
146FPFLAG_RARE(pipe_check_stat);
147FPFLAG_RARE(pipe_check_poll);
148
149#undef FPFLAG
150#undef FPFLAG_RARE
151
152/*
153 * Labels consist of a indexed set of "slots", which are allocated policies
154 * as required.  The MAC Framework maintains a bitmask of slots allocated so
155 * far to prevent reuse.  Slots cannot be reused, as the MAC Framework
156 * guarantees that newly allocated slots in labels will be NULL unless
157 * otherwise initialized, and because we do not have a mechanism to garbage
158 * collect slots on policy unload.  As labeled policies tend to be statically
159 * loaded during boot, and not frequently unloaded and reloaded, this is not
160 * generally an issue.
161 */
162#if MAC_MAX_SLOTS > 32
163#error "MAC_MAX_SLOTS too large"
164#endif
165
166static unsigned int mac_max_slots = MAC_MAX_SLOTS;
167static unsigned int mac_slot_offsets_free = (1 << MAC_MAX_SLOTS) - 1;
168SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD, &mac_max_slots,
169    0, "");
170
171/*
172 * Has the kernel started generating labeled objects yet?  All read/write
173 * access to this variable is serialized during the boot process.  Following
174 * the end of serialization, we don't update this flag; no locking.
175 */
176static int	mac_late = 0;
177
178/*
179 * Each policy declares a mask of object types requiring labels to be
180 * allocated for them.  For convenience, we combine and cache the bitwise or
181 * of the per-policy object flags to track whether we will allocate a label
182 * for an object type at run-time.
183 */
184uint64_t	mac_labeled;
185SYSCTL_UQUAD(_security_mac, OID_AUTO, labeled, CTLFLAG_RD, &mac_labeled, 0,
186    "Mask of object types being labeled");
187
188MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage");
189
190/*
191 * MAC policy modules are placed in one of two lists: mac_static_policy_list,
192 * for policies that are loaded early and cannot be unloaded, and
193 * mac_policy_list, which holds policies either loaded later in the boot
194 * cycle or that may be unloaded.  The static policy list does not require
195 * locks to iterate over, but the dynamic list requires synchronization.
196 * Support for dynamic policy loading can be compiled out using the
197 * MAC_STATIC kernel option.
198 *
199 * The dynamic policy list is protected by two locks: modifying the list
200 * requires both locks to be held exclusively.  One of the locks,
201 * mac_policy_rm, is acquired over policy entry points that will never sleep;
202 * the other, mac_policy_rms, is acquired over policy entry points that may
203 * sleep.  The former category will be used when kernel locks may be held
204 * over calls to the MAC Framework, during network processing in ithreads,
205 * etc.  The latter will tend to involve potentially blocking memory
206 * allocations, extended attribute I/O, etc.
207 */
208#ifndef MAC_STATIC
209static struct rmlock mac_policy_rm;	/* Non-sleeping entry points. */
210static struct rmslock mac_policy_rms;	/* Sleeping entry points. */
211#endif
212
213struct mac_policy_list_head mac_policy_list;
214struct mac_policy_list_head mac_static_policy_list;
215u_int mac_policy_count;			/* Registered policy count. */
216
217static void	mac_policy_xlock(void);
218static void	mac_policy_xlock_assert(void);
219static void	mac_policy_xunlock(void);
220
221void
222mac_policy_slock_nosleep(struct rm_priotracker *tracker)
223{
224
225#ifndef MAC_STATIC
226	if (!mac_late)
227		return;
228
229	rm_rlock(&mac_policy_rm, tracker);
230#endif
231}
232
233void
234mac_policy_slock_sleep(void)
235{
236
237	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
238 	    "mac_policy_slock_sleep");
239
240#ifndef MAC_STATIC
241	if (!mac_late)
242		return;
243
244	rms_rlock(&mac_policy_rms);
245#endif
246}
247
248void
249mac_policy_sunlock_nosleep(struct rm_priotracker *tracker)
250{
251
252#ifndef MAC_STATIC
253	if (!mac_late)
254		return;
255
256	rm_runlock(&mac_policy_rm, tracker);
257#endif
258}
259
260void
261mac_policy_sunlock_sleep(void)
262{
263
264#ifndef MAC_STATIC
265	if (!mac_late)
266		return;
267
268	rms_runlock(&mac_policy_rms);
269#endif
270}
271
272static void
273mac_policy_xlock(void)
274{
275
276	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
277 	    "mac_policy_xlock()");
278
279#ifndef MAC_STATIC
280	if (!mac_late)
281		return;
282
283	rms_wlock(&mac_policy_rms);
284	rm_wlock(&mac_policy_rm);
285#endif
286}
287
288static void
289mac_policy_xunlock(void)
290{
291
292#ifndef MAC_STATIC
293	if (!mac_late)
294		return;
295
296	rm_wunlock(&mac_policy_rm);
297	rms_wunlock(&mac_policy_rms);
298#endif
299}
300
301static void
302mac_policy_xlock_assert(void)
303{
304
305#ifndef MAC_STATIC
306	if (!mac_late)
307		return;
308
309	rm_assert(&mac_policy_rm, RA_WLOCKED);
310#endif
311}
312
313/*
314 * Initialize the MAC subsystem, including appropriate SMP locks.
315 */
316static void
317mac_init(void)
318{
319
320	LIST_INIT(&mac_static_policy_list);
321	LIST_INIT(&mac_policy_list);
322	mac_labelzone_init();
323
324#ifndef MAC_STATIC
325	rm_init_flags(&mac_policy_rm, "mac_policy_rm", RM_NOWITNESS |
326	    RM_RECURSE);
327	rms_init(&mac_policy_rms, "mac_policy_rms");
328#endif
329}
330
331/*
332 * For the purposes of modules that want to know if they were loaded "early",
333 * set the mac_late flag once we've processed modules either linked into the
334 * kernel, or loaded before the kernel startup.
335 */
336static void
337mac_late_init(void)
338{
339
340	mac_late = 1;
341}
342
343/*
344 * Given a policy, derive from its set of non-NULL label init methods what
345 * object types the policy is interested in.
346 */
347static uint64_t
348mac_policy_getlabeled(struct mac_policy_conf *mpc)
349{
350	uint64_t labeled;
351
352#define	MPC_FLAG(method, flag)					\
353	if (mpc->mpc_ops->mpo_ ## method != NULL)			\
354		labeled |= (flag);					\
355
356	labeled = 0;
357	MPC_FLAG(cred_init_label, MPC_OBJECT_CRED);
358	MPC_FLAG(proc_init_label, MPC_OBJECT_PROC);
359	MPC_FLAG(vnode_init_label, MPC_OBJECT_VNODE);
360	MPC_FLAG(inpcb_init_label, MPC_OBJECT_INPCB);
361	MPC_FLAG(socket_init_label, MPC_OBJECT_SOCKET);
362	MPC_FLAG(devfs_init_label, MPC_OBJECT_DEVFS);
363	MPC_FLAG(mbuf_init_label, MPC_OBJECT_MBUF);
364	MPC_FLAG(ipq_init_label, MPC_OBJECT_IPQ);
365	MPC_FLAG(ifnet_init_label, MPC_OBJECT_IFNET);
366	MPC_FLAG(bpfdesc_init_label, MPC_OBJECT_BPFDESC);
367	MPC_FLAG(pipe_init_label, MPC_OBJECT_PIPE);
368	MPC_FLAG(mount_init_label, MPC_OBJECT_MOUNT);
369	MPC_FLAG(posixsem_init_label, MPC_OBJECT_POSIXSEM);
370	MPC_FLAG(posixshm_init_label, MPC_OBJECT_POSIXSHM);
371	MPC_FLAG(sysvmsg_init_label, MPC_OBJECT_SYSVMSG);
372	MPC_FLAG(sysvmsq_init_label, MPC_OBJECT_SYSVMSQ);
373	MPC_FLAG(sysvsem_init_label, MPC_OBJECT_SYSVSEM);
374	MPC_FLAG(sysvshm_init_label, MPC_OBJECT_SYSVSHM);
375	MPC_FLAG(syncache_init_label, MPC_OBJECT_SYNCACHE);
376	MPC_FLAG(ip6q_init_label, MPC_OBJECT_IP6Q);
377
378#undef MPC_FLAG
379	return (labeled);
380}
381
382/*
383 * When policies are loaded or unloaded, walk the list of registered policies
384 * and built mac_labeled, a bitmask representing the union of all objects
385 * requiring labels across all policies.
386 */
387static void
388mac_policy_update(void)
389{
390	struct mac_policy_conf *mpc;
391
392	mac_policy_xlock_assert();
393
394	mac_labeled = 0;
395	mac_policy_count = 0;
396	LIST_FOREACH(mpc, &mac_static_policy_list, mpc_list) {
397		mac_labeled |= mac_policy_getlabeled(mpc);
398		mac_policy_count++;
399	}
400	LIST_FOREACH(mpc, &mac_policy_list, mpc_list) {
401		mac_labeled |= mac_policy_getlabeled(mpc);
402		mac_policy_count++;
403	}
404
405	cache_fast_lookup_enabled_recalc();
406}
407
408/*
409 * There are frequently used code paths which check for rarely installed
410 * policies. Gross hack below enables doing it in a cheap manner.
411 */
412
413#define FPO(f)	(offsetof(struct mac_policy_ops, mpo_##f) / sizeof(uintptr_t))
414
415struct mac_policy_fastpath_elem {
416	int	count;
417	bool	*flag;
418	size_t	offset;
419};
420
421struct mac_policy_fastpath_elem mac_policy_fastpath_array[] = {
422	{ .offset = FPO(priv_check), .flag = &mac_priv_check_fp_flag },
423	{ .offset = FPO(priv_grant), .flag = &mac_priv_grant_fp_flag },
424	{ .offset = FPO(vnode_check_lookup),
425		.flag = &mac_vnode_check_lookup_fp_flag },
426	{ .offset = FPO(vnode_check_readlink),
427		.flag = &mac_vnode_check_readlink_fp_flag },
428	{ .offset = FPO(vnode_check_open),
429		.flag = &mac_vnode_check_open_fp_flag },
430	{ .offset = FPO(vnode_check_stat),
431		.flag = &mac_vnode_check_stat_fp_flag },
432	{ .offset = FPO(vnode_check_read),
433		.flag = &mac_vnode_check_read_fp_flag },
434	{ .offset = FPO(vnode_check_write),
435		.flag = &mac_vnode_check_write_fp_flag },
436	{ .offset = FPO(vnode_check_mmap),
437		.flag = &mac_vnode_check_mmap_fp_flag },
438	{ .offset = FPO(vnode_check_poll),
439		.flag = &mac_vnode_check_poll_fp_flag },
440	{ .offset = FPO(vnode_check_rename_from),
441		.flag = &mac_vnode_check_rename_from_fp_flag },
442	{ .offset = FPO(vnode_check_access),
443		.flag = &mac_vnode_check_access_fp_flag },
444	{ .offset = FPO(pipe_check_stat),
445		.flag = &mac_pipe_check_stat_fp_flag },
446	{ .offset = FPO(pipe_check_poll),
447		.flag = &mac_pipe_check_poll_fp_flag },
448};
449
450static void
451mac_policy_fastpath_enable(struct mac_policy_fastpath_elem *mpfe)
452{
453
454	MPASS(mpfe->count >= 0);
455	mpfe->count++;
456	if (mpfe->count == 1) {
457		MPASS(*mpfe->flag == false);
458		*mpfe->flag = true;
459	}
460}
461
462static void
463mac_policy_fastpath_disable(struct mac_policy_fastpath_elem *mpfe)
464{
465
466	MPASS(mpfe->count >= 1);
467	mpfe->count--;
468	if (mpfe->count == 0) {
469		MPASS(*mpfe->flag == true);
470		*mpfe->flag = false;
471	}
472}
473
474static void
475mac_policy_fastpath_register(struct mac_policy_conf *mpc)
476{
477	struct mac_policy_fastpath_elem *mpfe;
478	uintptr_t **ops;
479	int i;
480
481	mac_policy_xlock_assert();
482
483	ops = (uintptr_t **)mpc->mpc_ops;
484	for (i = 0; i < nitems(mac_policy_fastpath_array); i++) {
485		mpfe = &mac_policy_fastpath_array[i];
486		if (ops[mpfe->offset] != NULL)
487			mac_policy_fastpath_enable(mpfe);
488	}
489}
490
491static void
492mac_policy_fastpath_unregister(struct mac_policy_conf *mpc)
493{
494	struct mac_policy_fastpath_elem *mpfe;
495	uintptr_t **ops;
496	int i;
497
498	mac_policy_xlock_assert();
499
500	ops = (uintptr_t **)mpc->mpc_ops;
501	for (i = 0; i < nitems(mac_policy_fastpath_array); i++) {
502		mpfe = &mac_policy_fastpath_array[i];
503		if (ops[mpfe->offset] != NULL)
504			mac_policy_fastpath_disable(mpfe);
505	}
506}
507
508#undef FPO
509
510static int
511mac_policy_register(struct mac_policy_conf *mpc)
512{
513	struct mac_policy_conf *tmpc;
514	int error, slot, static_entry;
515
516	error = 0;
517
518	/*
519	 * We don't technically need exclusive access while !mac_late, but
520	 * hold it for assertion consistency.
521	 */
522	mac_policy_xlock();
523
524	/*
525	 * If the module can potentially be unloaded, or we're loading late,
526	 * we have to stick it in the non-static list and pay an extra
527	 * performance overhead.  Otherwise, we can pay a light locking cost
528	 * and stick it in the static list.
529	 */
530	static_entry = (!mac_late &&
531	    !(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK));
532
533	if (static_entry) {
534		LIST_FOREACH(tmpc, &mac_static_policy_list, mpc_list) {
535			if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) {
536				error = EEXIST;
537				goto out;
538			}
539		}
540	} else {
541		LIST_FOREACH(tmpc, &mac_policy_list, mpc_list) {
542			if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) {
543				error = EEXIST;
544				goto out;
545			}
546		}
547	}
548	if (mpc->mpc_field_off != NULL) {
549		slot = ffs(mac_slot_offsets_free);
550		if (slot == 0) {
551			error = ENOMEM;
552			goto out;
553		}
554		slot--;
555		mac_slot_offsets_free &= ~(1 << slot);
556		*mpc->mpc_field_off = slot;
557	}
558	mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED;
559
560	/*
561	 * If we're loading a MAC module after the framework has initialized,
562	 * it has to go into the dynamic list.  If we're loading it before
563	 * we've finished initializing, it can go into the static list with
564	 * weaker locker requirements.
565	 */
566	if (static_entry)
567		LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list);
568	else
569		LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list);
570
571	/*
572	 * Per-policy initialization.  Currently, this takes place under the
573	 * exclusive lock, so policies must not sleep in their init method.
574	 * In the future, we may want to separate "init" from "start", with
575	 * "init" occurring without the lock held.  Likewise, on tear-down,
576	 * breaking out "stop" from "destroy".
577	 */
578	if (mpc->mpc_ops->mpo_init != NULL)
579		(*(mpc->mpc_ops->mpo_init))(mpc);
580
581	mac_policy_fastpath_register(mpc);
582
583	mac_policy_update();
584
585	SDT_PROBE1(mac, , policy, register, mpc);
586	printf("Security policy loaded: %s (%s)\n", mpc->mpc_fullname,
587	    mpc->mpc_name);
588
589out:
590	mac_policy_xunlock();
591	return (error);
592}
593
594static int
595mac_policy_unregister(struct mac_policy_conf *mpc)
596{
597
598	/*
599	 * If we fail the load, we may get a request to unload.  Check to see
600	 * if we did the run-time registration, and if not, silently succeed.
601	 */
602	mac_policy_xlock();
603	if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) {
604		mac_policy_xunlock();
605		return (0);
606	}
607#if 0
608	/*
609	 * Don't allow unloading modules with private data.
610	 */
611	if (mpc->mpc_field_off != NULL) {
612		mac_policy_xunlock();
613		return (EBUSY);
614	}
615#endif
616	/*
617	 * Only allow the unload to proceed if the module is unloadable by
618	 * its own definition.
619	 */
620	if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) {
621		mac_policy_xunlock();
622		return (EBUSY);
623	}
624
625	mac_policy_fastpath_unregister(mpc);
626
627	if (mpc->mpc_ops->mpo_destroy != NULL)
628		(*(mpc->mpc_ops->mpo_destroy))(mpc);
629
630	LIST_REMOVE(mpc, mpc_list);
631	mpc->mpc_runtime_flags &= ~MPC_RUNTIME_FLAG_REGISTERED;
632	mac_policy_update();
633	mac_policy_xunlock();
634
635	SDT_PROBE1(mac, , policy, unregister, mpc);
636	printf("Security policy unload: %s (%s)\n", mpc->mpc_fullname,
637	    mpc->mpc_name);
638
639	return (0);
640}
641
642/*
643 * Allow MAC policy modules to register during boot, etc.
644 */
645int
646mac_policy_modevent(module_t mod, int type, void *data)
647{
648	struct mac_policy_conf *mpc;
649	int error;
650
651	error = 0;
652	mpc = (struct mac_policy_conf *) data;
653
654#ifdef MAC_STATIC
655	if (mac_late) {
656		printf("mac_policy_modevent: MAC_STATIC and late\n");
657		return (EBUSY);
658	}
659#endif
660
661	SDT_PROBE2(mac, , policy, modevent, type, mpc);
662	switch (type) {
663	case MOD_LOAD:
664		if (mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_NOTLATE &&
665		    mac_late) {
666			printf("mac_policy_modevent: can't load %s policy "
667			    "after booting\n", mpc->mpc_name);
668			error = EBUSY;
669			break;
670		}
671		error = mac_policy_register(mpc);
672		break;
673	case MOD_UNLOAD:
674		/* Don't unregister the module if it was never registered. */
675		if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED)
676		    != 0)
677			error = mac_policy_unregister(mpc);
678		else
679			error = 0;
680		break;
681	default:
682		error = EOPNOTSUPP;
683		break;
684	}
685
686	return (error);
687}
688
689/*
690 * Define an error value precedence, and given two arguments, selects the
691 * value with the higher precedence.
692 */
693int
694mac_error_select(int error1, int error2)
695{
696
697	/* Certain decision-making errors take top priority. */
698	if (error1 == EDEADLK || error2 == EDEADLK)
699		return (EDEADLK);
700
701	/* Invalid arguments should be reported where possible. */
702	if (error1 == EINVAL || error2 == EINVAL)
703		return (EINVAL);
704
705	/* Precedence goes to "visibility", with both process and file. */
706	if (error1 == ESRCH || error2 == ESRCH)
707		return (ESRCH);
708
709	if (error1 == ENOENT || error2 == ENOENT)
710		return (ENOENT);
711
712	/* Precedence goes to DAC/MAC protections. */
713	if (error1 == EACCES || error2 == EACCES)
714		return (EACCES);
715
716	/* Precedence goes to privilege. */
717	if (error1 == EPERM || error2 == EPERM)
718		return (EPERM);
719
720	/* Precedence goes to error over success; otherwise, arbitrary. */
721	if (error1 != 0)
722		return (error1);
723	return (error2);
724}
725
726int
727mac_check_structmac_consistent(struct mac *mac)
728{
729
730	/* Require that labels have a non-zero length. */
731	if (mac->m_buflen > MAC_MAX_LABEL_BUF_LEN ||
732	    mac->m_buflen <= sizeof(""))
733		return (EINVAL);
734
735	return (0);
736}
737
738SYSINIT(mac, SI_SUB_MAC, SI_ORDER_FIRST, mac_init, NULL);
739SYSINIT(mac_late, SI_SUB_MAC_LATE, SI_ORDER_FIRST, mac_late_init, NULL);
740