summaryrefslogtreecommitdiffstats
path: root/security/landlock/ruleset.c
blob: e0a5fbf9201ade7036e8cb8203f5b99e18b94947 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Landlock LSM - Ruleset management
 *
 * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
 * Copyright © 2018-2020 ANSSI
 */

#include <linux/bits.h>
#include <linux/bug.h>
#include <linux/compiler_types.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/lockdep.h>
#include <linux/overflow.h>
#include <linux/rbtree.h>
#include <linux/refcount.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>

#include "limits.h"
#include "object.h"
#include "ruleset.h"

static struct landlock_ruleset *create_ruleset(const u32 num_layers)
{
	struct landlock_ruleset *new_ruleset;

	new_ruleset =
		kzalloc(struct_size(new_ruleset, access_masks, num_layers),
			GFP_KERNEL_ACCOUNT);
	if (!new_ruleset)
		return ERR_PTR(-ENOMEM);
	refcount_set(&new_ruleset->usage, 1);
	mutex_init(&new_ruleset->lock);
	new_ruleset->root_inode = RB_ROOT;

#if IS_ENABLED(CONFIG_INET)
	new_ruleset->root_net_port = RB_ROOT;
#endif /* IS_ENABLED(CONFIG_INET) */

	new_ruleset->num_layers = num_layers;
	/*
	 * hierarchy = NULL
	 * num_rules = 0
	 * access_masks[] = 0
	 */
	return new_ruleset;
}

struct landlock_ruleset *
landlock_create_ruleset(const access_mask_t fs_access_mask,
			const access_mask_t net_access_mask)
{
	struct landlock_ruleset *new_ruleset;

	/* Informs about useless ruleset. */
	if (!fs_access_mask && !net_access_mask)
		return ERR_PTR(-ENOMSG);
	new_ruleset = create_ruleset(1);
	if (IS_ERR(new_ruleset))
		return new_ruleset;
	if (fs_access_mask)
		landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
	if (net_access_mask)
		landlock_add_net_access_mask(new_ruleset, net_access_mask, 0);
	return new_ruleset;
}

static void build_check_rule(void)
{
	const struct landlock_rule rule = {
		.num_layers = ~0,
	};

	BUILD_BUG_ON(rule.num_layers < LANDLOCK_MAX_NUM_LAYERS);
}

static bool is_object_pointer(const enum landlock_key_type key_type)
{
	switch (key_type) {
	case LANDLOCK_KEY_INODE:
		return true;

#if IS_ENABLED(CONFIG_INET)
	case LANDLOCK_KEY_NET_PORT:
		return false;
#endif /* IS_ENABLED(CONFIG_INET) */

	default:
		WARN_ON_ONCE(1);
		return false;
	}
}

static struct landlock_rule *
create_rule(const struct landlock_id id,
	    const struct landlock_layer (*const layers)[], const u32 num_layers,
	    const struct landlock_layer *const new_layer)
{
	struct landlock_rule *new_rule;
	u32 new_num_layers;

	build_check_rule();
	if (new_layer) {
		/* Should already be checked by landlock_merge_ruleset(). */
		if (WARN_ON_ONCE(num_layers >= LANDLOCK_MAX_NUM_LAYERS))
			return ERR_PTR(-E2BIG);
		new_num_layers = num_layers + 1;
	} else {
		new_num_layers = num_layers;
	}
	new_rule = kzalloc(struct_size(new_rule, layers, new_num_layers),
			   GFP_KERNEL_ACCOUNT);
	if (!new_rule)
		return ERR_PTR(-ENOMEM);
	RB_CLEAR_NODE(&new_rule->node);
	if (is_object_pointer(id.type)) {
		/* This should be catched by insert_rule(). */
		WARN_ON_ONCE(!id.key.object);
		landlock_get_object(id.key.object);
	}

	new_rule->key = id.key;
	new_rule->num_layers = new_num_layers;
	/* Copies the original layer stack. */
	memcpy(new_rule->layers, layers,
	       flex_array_size(new_rule, layers, num_layers));
	if (new_layer)
		/* Adds a copy of @new_layer on the layer stack. */
		new_rule->layers[new_rule->num_layers - 1] = *new_layer;
	return new_rule;
}

static struct rb_root *get_root(struct landlock_ruleset *const ruleset,
				const enum landlock_key_type key_type)
{
	switch (key_type) {
	case LANDLOCK_KEY_INODE:
		return &ruleset->root_inode;

#if IS_ENABLED(CONFIG_INET)
	case LANDLOCK_KEY_NET_PORT:
		return &ruleset->root_net_port;
#endif /* IS_ENABLED(CONFIG_INET) */

	default:
		WARN_ON_ONCE(1);
		return ERR_PTR(-EINVAL);
	}
}

static void free_rule(struct landlock_rule *const rule,
		      const enum landlock_key_type key_type)
{
	might_sleep();
	if (!rule)
		return;
	if (is_object_pointer(key_type))
		landlock_put_object(rule->key.object);
	kfree(rule);
}

static void build_check_ruleset(void)
{
	const struct landlock_ruleset ruleset = {
		.num_rules = ~0,
		.num_layers = ~0,
	};
	typeof(ruleset.access_masks[0]) access_masks = ~0;

	BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
	BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
	BUILD_BUG_ON(access_masks <
		     ((LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) |
		      (LANDLOCK_MASK_ACCESS_NET << LANDLOCK_SHIFT_ACCESS_NET)));
}

/**
 * insert_rule - Create and insert a rule in a ruleset
 *
 * @ruleset: The ruleset to be updated.
 * @id: The ID to build the new rule with.  The underlying kernel object, if
 *      any, must be held by the caller.
 * @layers: One or multiple layers to be copied into the new rule.
 * @num_layers: The number of @layers entries.
 *
 * When user space requests to add a new rule to a ruleset, @layers only
 * contains one entry and this entry is not assigned to any level.  In this
 * case, the new rule will extend @ruleset, similarly to a boolean OR between
 * access rights.
 *
 * When merging a ruleset in a domain, or copying a domain, @layers will be
 * added to @ruleset as new constraints, similarly to a boolean AND between
 * access rights.
 */
static int insert_rule(struct landlock_ruleset *const ruleset,
		       const struct landlock_id id,
		       const struct landlock_layer (*const layers)[],
		       const size_t num_layers)
{
	struct rb_node **walker_node;
	struct rb_node *parent_node = NULL;
	struct landlock_rule *new_rule;
	struct rb_root *root;

	might_sleep();
	lockdep_assert_held(&ruleset->lock);
	if (WARN_ON_ONCE(!layers))
		return -ENOENT;

	if (is_object_pointer(id.type) && WARN_ON_ONCE(!id.key.object))
		return -ENOENT;

	root = get_root(ruleset, id.type);
	if (IS_ERR(root))
		return PTR_ERR(root);

	walker_node = &root->rb_node;
	while (*walker_node) {
		struct landlock_rule *const this =
			rb_entry(*walker_node, struct landlock_rule, node);

		if (this->key.data != id.key.data) {
			parent_node = *walker_node;
			if (this->key.data < id.key.data)
				walker_node = &((*walker_node)->rb_right);
			else
				walker_node = &((*walker_node)->rb_left);
			continue;
		}

		/* Only a single-level layer should match an existing rule. */
		if (WARN_ON_ONCE(num_layers != 1))
			return -EINVAL;

		/* If there is a matching rule, updates it. */
		if ((*layers)[0].level == 0) {
			/*
			 * Extends access rights when the request comes from
			 * landlock_add_rule(2), i.e. @ruleset is not a domain.
			 */
			if (WARN_ON_ONCE(this->num_layers != 1))
				return -EINVAL;
			if (WARN_ON_ONCE(this->layers[0].level != 0))
				return -EINVAL;
			this->layers[0].access |= (*layers)[0].access;
			return 0;
		}

		if (WARN_ON_ONCE(this->layers[0].level == 0))
			return -EINVAL;

		/*
		 * Intersects access rights when it is a merge between a
		 * ruleset and a domain.
		 */
		new_rule = create_rule(id, &this->layers, this->num_layers,
				       &(*layers)[0]);
		if (IS_ERR(new_rule))
			return PTR_ERR(new_rule);
		rb_replace_node(&this->node, &new_rule->node, root);
		free_rule(this, id.type);
		return 0;
	}

	/* There is no match for @id. */
	build_check_ruleset();
	if (ruleset->num_rules >= LANDLOCK_MAX_NUM_RULES)
		return -E2BIG;
	new_rule = create_rule(id, layers, num_layers, NULL);
	if (IS_ERR(new_rule))
		return PTR_ERR(new_rule);
	rb_link_node(&new_rule->node, parent_node, walker_node);
	rb_insert_color(&new_rule->node, root);
	ruleset->num_rules++;
	return 0;
}

static void build_check_layer(void)
{
	const struct landlock_layer layer = {
		.level = ~0,
		.access = ~0,
	};

	BUILD_BUG_ON(layer.level < LANDLOCK_MAX_NUM_LAYERS);
	BUILD_BUG_ON(layer.access < LANDLOCK_MASK_ACCESS_FS);
}

/* @ruleset must be locked by the caller. */
int landlock_insert_rule(struct landlock_ruleset *const ruleset,
			 const struct landlock_id id,
			 const access_mask_t access)
{
	struct landlock_layer layers[] = { {
		.access = access,
		/* When @level is zero, insert_rule() extends @ruleset. */
		.level = 0,
	} };

	build_check_layer();
	return insert_rule(ruleset, id, &layers, ARRAY_SIZE(layers));
}

static void get_hierarchy(struct landlock_hierarchy *const hierarchy)
{
	if (hierarchy)
		refcount_inc(&hierarchy->usage);
}

static void put_hierarchy(struct landlock_hierarchy *hierarchy)
{
	while (hierarchy && refcount_dec_and_test(&hierarchy->usage)) {
		const struct landlock_hierarchy *const freeme = hierarchy;

		hierarchy = hierarchy->parent;
		kfree(freeme);
	}
}

static int merge_tree(struct landlock_ruleset *const dst,
		      struct landlock_ruleset *const src,
		      const enum landlock_key_type key_type)
{
	struct landlock_rule *walker_rule, *next_rule;
	struct rb_root *src_root;
	int err = 0;

	might_sleep();
	lockdep_assert_held(&dst->lock);
	lockdep_assert_held(&src->lock);

	src_root = get_root(src, key_type);
	if (IS_ERR(src_root))
		return PTR_ERR(src_root);

	/* Merges the @src tree. */
	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, src_root,
					     node) {
		struct landlock_layer layers[] = { {
			.level = dst->num_layers,
		} };
		const struct landlock_id id = {
			.key = walker_rule->key,
			.type = key_type,
		};

		if (WARN_ON_ONCE(walker_rule->num_layers != 1))
			return -EINVAL;

		if (WARN_ON_ONCE(walker_rule->layers[0].level != 0))
			return -EINVAL;

		layers[0].access = walker_rule->layers[0].access;

		err = insert_rule(dst, id, &layers, ARRAY_SIZE(layers));
		if (err)
			return err;
	}
	return err;
}

static int merge_ruleset(struct landlock_ruleset *const dst,
			 struct landlock_ruleset *const src)
{
	int err = 0;

	might_sleep();
	/* Should already be checked by landlock_merge_ruleset() */
	if (WARN_ON_ONCE(!src))
		return 0;
	/* Only merge into a domain. */
	if (WARN_ON_ONCE(!dst || !dst->hierarchy))
		return -EINVAL;

	/* Locks @dst first because we are its only owner. */
	mutex_lock(&dst->lock);
	mutex_lock_nested(&src->lock, SINGLE_DEPTH_NESTING);

	/* Stacks the new layer. */
	if (WARN_ON_ONCE(src->num_layers != 1 || dst->num_layers < 1)) {
		err = -EINVAL;
		goto out_unlock;
	}
	dst->access_masks[dst->num_layers - 1] = src->access_masks[0];

	/* Merges the @src inode tree. */
	err = merge_tree(dst, src, LANDLOCK_KEY_INODE);
	if (err)
		goto out_unlock;

#if IS_ENABLED(CONFIG_INET)
	/* Merges the @src network port tree. */
	err = merge_tree(dst, src, LANDLOCK_KEY_NET_PORT);
	if (err)
		goto out_unlock;
#endif /* IS_ENABLED(CONFIG_INET) */

out_unlock:
	mutex_unlock(&src->lock);
	mutex_unlock(&dst->lock);
	return err;
}

static int inherit_tree(struct landlock_ruleset *const parent,
			struct landlock_ruleset *const child,
			const enum landlock_key_type key_type)
{
	struct landlock_rule *walker_rule, *next_rule;
	struct rb_root *parent_root;
	int err = 0;

	might_sleep();
	lockdep_assert_held(&parent->lock);
	lockdep_assert_held(&child->lock);

	parent_root = get_root(parent, key_type);
	if (IS_ERR(parent_root))
		return PTR_ERR(parent_root);

	/* Copies the @parent inode or network tree. */
	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
					     parent_root, node) {
		const struct landlock_id id = {
			.key = walker_rule->key,
			.type = key_type,
		};

		err = insert_rule(child, id, &walker_rule->layers,
				  walker_rule->num_layers);
		if (err)
			return err;
	}
	return err;
}

static int inherit_ruleset(struct landlock_ruleset *const parent,
			   struct landlock_ruleset *const child)
{
	int err = 0;

	might_sleep();
	if (!parent)
		return 0;

	/* Locks @child first because we are its only owner. */
	mutex_lock(&child->lock);
	mutex_lock_nested(&parent->lock, SINGLE_DEPTH_NESTING);

	/* Copies the @parent inode tree. */
	err = inherit_tree(parent, child, LANDLOCK_KEY_INODE);
	if (err)
		goto out_unlock;

#if IS_ENABLED(CONFIG_INET)
	/* Copies the @parent network port tree. */
	err = inherit_tree(parent, child, LANDLOCK_KEY_NET_PORT);
	if (err)
		goto out_unlock;
#endif /* IS_ENABLED(CONFIG_INET) */

	if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
		err = -EINVAL;
		goto out_unlock;
	}
	/* Copies the parent layer stack and leaves a space for the new layer. */
	memcpy(child->access_masks, parent->access_masks,
	       flex_array_size(parent, access_masks, parent->num_layers));

	if (WARN_ON_ONCE(!parent->hierarchy)) {
		err = -EINVAL;
		goto out_unlock;
	}
	get_hierarchy(parent->hierarchy);
	child->hierarchy->parent = parent->hierarchy;

out_unlock:
	mutex_unlock(&parent->lock);
	mutex_unlock(&child->lock);
	return err;
}

static void free_ruleset(struct landlock_ruleset *const ruleset)
{
	struct landlock_rule *freeme, *next;

	might_sleep();
	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
					     node)
		free_rule(freeme, LANDLOCK_KEY_INODE);

#if IS_ENABLED(CONFIG_INET)
	rbtree_postorder_for_each_entry_safe(freeme, next,
					     &ruleset->root_net_port, node)
		free_rule(freeme, LANDLOCK_KEY_NET_PORT);
#endif /* IS_ENABLED(CONFIG_INET) */

	put_hierarchy(ruleset->hierarchy);
	kfree(ruleset);
}

void landlock_put_ruleset(struct landlock_ruleset *const ruleset)
{
	might_sleep();
	if (ruleset && refcount_dec_and_test(&ruleset->usage))
		free_ruleset(ruleset);
}

static void free_ruleset_work(struct work_struct *const work)
{
	struct landlock_ruleset *ruleset;

	ruleset = container_of(work, struct landlock_ruleset, work_free);
	free_ruleset(ruleset);
}

void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset)
{
	if (ruleset && refcount_dec_and_test(&ruleset->usage)) {
		INIT_WORK(&ruleset->work_free, free_ruleset_work);
		schedule_work(&ruleset->work_free);
	}
}

/**
 * landlock_merge_ruleset - Merge a ruleset with a domain
 *
 * @parent: Parent domain.
 * @ruleset: New ruleset to be merged.
 *
 * Returns the intersection of @parent and @ruleset, or returns @parent if
 * @ruleset is empty, or returns a duplicate of @ruleset if @parent is empty.
 */
struct landlock_ruleset *
landlock_merge_ruleset(struct landlock_ruleset *const parent,
		       struct landlock_ruleset *const ruleset)
{
	struct landlock_ruleset *new_dom;
	u32 num_layers;
	int err;

	might_sleep();
	if (WARN_ON_ONCE(!ruleset || parent == ruleset))
		return ERR_PTR(-EINVAL);

	if (parent) {
		if (parent->num_layers >= LANDLOCK_MAX_NUM_LAYERS)
			return ERR_PTR(-E2BIG);
		num_layers = parent->num_layers + 1;
	} else {
		num_layers = 1;
	}

	/* Creates a new domain... */
	new_dom = create_ruleset(num_layers);
	if (IS_ERR(new_dom))
		return new_dom;
	new_dom->hierarchy =
		kzalloc(sizeof(*new_dom->hierarchy), GFP_KERNEL_ACCOUNT);
	if (!new_dom->hierarchy) {
		err = -ENOMEM;
		goto out_put_dom;
	}
	refcount_set(&new_dom->hierarchy->usage, 1);

	/* ...as a child of @parent... */
	err = inherit_ruleset(parent, new_dom);
	if (err)
		goto out_put_dom;

	/* ...and including @ruleset. */
	err = merge_ruleset(new_dom, ruleset);
	if (err)
		goto out_put_dom;

	return new_dom;

out_put_dom:
	landlock_put_ruleset(new_dom);
	return ERR_PTR(err);
}

/*
 * The returned access has the same lifetime as @ruleset.
 */
const struct landlock_rule *
landlock_find_rule(const struct landlock_ruleset *const ruleset,
		   const struct landlock_id id)
{
	const struct rb_root *root;
	const struct rb_node *node;

	root = get_root((struct landlock_ruleset *)ruleset, id.type);
	if (IS_ERR(root))
		return NULL;
	node = root->rb_node;

	while (node) {
		struct landlock_rule *this =
			rb_entry(node, struct landlock_rule, node);

		if (this->key.data == id.key.data)
			return this;
		if (this->key.data < id.key.data)
			node = node->rb_right;
		else
			node = node->rb_left;
	}
	return NULL;
}

/*
 * @layer_masks is read and may be updated according to the access request and
 * the matching rule.
 * @masks_array_size must be equal to ARRAY_SIZE(*layer_masks).
 *
 * Returns true if the request is allowed (i.e. relevant layer masks for the
 * request are empty).
 */
bool landlock_unmask_layers(const struct landlock_rule *const rule,
			    const access_mask_t access_request,
			    layer_mask_t (*const layer_masks)[],
			    const size_t masks_array_size)
{
	size_t layer_level;

	if (!access_request || !layer_masks)
		return true;
	if (!rule)
		return false;

	/*
	 * An access is granted if, for each policy layer, at least one rule
	 * encountered on the pathwalk grants the requested access,
	 * regardless of its position in the layer stack.  We must then check
	 * the remaining layers for each inode, from the first added layer to
	 * the last one.  When there is multiple requested accesses, for each
	 * policy layer, the full set of requested accesses may not be granted
	 * by only one rule, but by the union (binary OR) of multiple rules.
	 * E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
	 */
	for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
		const struct landlock_layer *const layer =
			&rule->layers[layer_level];
		const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
		const unsigned long access_req = access_request;
		unsigned long access_bit;
		bool is_empty;

		/*
		 * Records in @layer_masks which layer grants access to each
		 * requested access.
		 */
		is_empty = true;
		for_each_set_bit(access_bit, &access_req, masks_array_size) {
			if (layer->access & BIT_ULL(access_bit))
				(*layer_masks)[access_bit] &= ~layer_bit;
			is_empty = is_empty && !(*layer_masks)[access_bit];
		}
		if (is_empty)
			return true;
	}
	return false;
}

typedef access_mask_t
get_access_mask_t(const struct landlock_ruleset *const ruleset,
		  const u16 layer_level);

/**
 * landlock_init_layer_masks - Initialize layer masks from an access request
 *
 * Populates @layer_masks such that for each access right in @access_request,
 * the bits for all the layers are set where this access right is handled.
 *
 * @domain: The domain that defines the current restrictions.
 * @access_request: The requested access rights to check.
 * @layer_masks: It must contain %LANDLOCK_NUM_ACCESS_FS or
 * %LANDLOCK_NUM_ACCESS_NET elements according to @key_type.
 * @key_type: The key type to switch between access masks of different types.
 *
 * Returns: An access mask where each access right bit is set which is handled
 * in any of the active layers in @domain.
 */
access_mask_t
landlock_init_layer_masks(const struct landlock_ruleset *const domain,
			  const access_mask_t access_request,
			  layer_mask_t (*const layer_masks)[],
			  const enum landlock_key_type key_type)
{
	access_mask_t handled_accesses = 0;
	size_t layer_level, num_access;
	get_access_mask_t *get_access_mask;

	switch (key_type) {
	case LANDLOCK_KEY_INODE:
		get_access_mask = landlock_get_fs_access_mask;
		num_access = LANDLOCK_NUM_ACCESS_FS;
		break;

#if IS_ENABLED(CONFIG_INET)
	case LANDLOCK_KEY_NET_PORT:
		get_access_mask = landlock_get_net_access_mask;
		num_access = LANDLOCK_NUM_ACCESS_NET;
		break;
#endif /* IS_ENABLED(CONFIG_INET) */

	default:
		WARN_ON_ONCE(1);
		return 0;
	}

	memset(layer_masks, 0,
	       array_size(sizeof((*layer_masks)[0]), num_access));

	/* An empty access request can happen because of O_WRONLY | O_RDWR. */
	if (!access_request)
		return 0;

	/* Saves all handled accesses per layer. */
	for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
		const unsigned long access_req = access_request;
		const access_mask_t access_mask =
			get_access_mask(domain, layer_level);
		unsigned long access_bit;

		for_each_set_bit(access_bit, &access_req, num_access) {
			if (BIT_ULL(access_bit) & access_mask) {
				(*layer_masks)[access_bit] |=
					BIT_ULL(layer_level);
				handled_accesses |= BIT_ULL(access_bit);
			}
		}
	}
	return handled_accesses;
}