Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
  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
// SPDX-License-Identifier: GPL-2.0
/*
 * Implementation of the SID table type.
 *
 * Original author: Stephen Smalley, <sds@tycho.nsa.gov>
 * Author: Ondrej Mosnacek, <omosnacek@gmail.com>
 *
 * Copyright (C) 2018 Red Hat, Inc.
 */
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <asm/barrier.h>
#include "flask.h"
#include "security.h"
#include "sidtab.h"

int sidtab_init(struct sidtab *s)
{
	u32 i;

	memset(s->roots, 0, sizeof(s->roots));

	/* max count is SIDTAB_MAX so valid index is always < SIDTAB_MAX */
	for (i = 0; i < SIDTAB_RCACHE_SIZE; i++)
		s->rcache[i] = SIDTAB_MAX;

	for (i = 0; i < SECINITSID_NUM; i++)
		s->isids[i].set = 0;

	s->count = 0;
	s->convert = NULL;

	spin_lock_init(&s->lock);
	return 0;
}

int sidtab_set_initial(struct sidtab *s, u32 sid, struct context *context)
{
	struct sidtab_isid_entry *entry;
	int rc;

	if (sid == 0 || sid > SECINITSID_NUM)
		return -EINVAL;

	entry = &s->isids[sid - 1];

	rc = context_cpy(&entry->context, context);
	if (rc)
		return rc;

	entry->set = 1;
	return 0;
}

static u32 sidtab_level_from_count(u32 count)
{
	u32 capacity = SIDTAB_LEAF_ENTRIES;
	u32 level = 0;

	while (count > capacity) {
		capacity <<= SIDTAB_INNER_SHIFT;
		++level;
	}
	return level;
}

static int sidtab_alloc_roots(struct sidtab *s, u32 level)
{
	u32 l;

	if (!s->roots[0].ptr_leaf) {
		s->roots[0].ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
					       GFP_ATOMIC);
		if (!s->roots[0].ptr_leaf)
			return -ENOMEM;
	}
	for (l = 1; l <= level; ++l)
		if (!s->roots[l].ptr_inner) {
			s->roots[l].ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
							GFP_ATOMIC);
			if (!s->roots[l].ptr_inner)
				return -ENOMEM;
			s->roots[l].ptr_inner->entries[0] = s->roots[l - 1];
		}
	return 0;
}

static struct context *sidtab_do_lookup(struct sidtab *s, u32 index, int alloc)
{
	union sidtab_entry_inner *entry;
	u32 level, capacity_shift, leaf_index = index / SIDTAB_LEAF_ENTRIES;

	/* find the level of the subtree we need */
	level = sidtab_level_from_count(index + 1);
	capacity_shift = level * SIDTAB_INNER_SHIFT;

	/* allocate roots if needed */
	if (alloc && sidtab_alloc_roots(s, level) != 0)
		return NULL;

	/* lookup inside the subtree */
	entry = &s->roots[level];
	while (level != 0) {
		capacity_shift -= SIDTAB_INNER_SHIFT;
		--level;

		entry = &entry->ptr_inner->entries[leaf_index >> capacity_shift];
		leaf_index &= ((u32)1 << capacity_shift) - 1;

		if (!entry->ptr_inner) {
			if (alloc)
				entry->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
							   GFP_ATOMIC);
			if (!entry->ptr_inner)
				return NULL;
		}
	}
	if (!entry->ptr_leaf) {
		if (alloc)
			entry->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
						  GFP_ATOMIC);
		if (!entry->ptr_leaf)
			return NULL;
	}
	return &entry->ptr_leaf->entries[index % SIDTAB_LEAF_ENTRIES].context;
}

static struct context *sidtab_lookup(struct sidtab *s, u32 index)
{
	/* read entries only after reading count */
	u32 count = smp_load_acquire(&s->count);

	if (index >= count)
		return NULL;

	return sidtab_do_lookup(s, index, 0);
}

static struct context *sidtab_lookup_initial(struct sidtab *s, u32 sid)
{
	return s->isids[sid - 1].set ? &s->isids[sid - 1].context : NULL;
}

static struct context *sidtab_search_core(struct sidtab *s, u32 sid, int force)
{
	struct context *context;

	if (sid != 0) {
		if (sid > SECINITSID_NUM)
			context = sidtab_lookup(s, sid - (SECINITSID_NUM + 1));
		else
			context = sidtab_lookup_initial(s, sid);
		if (context && (!context->len || force))
			return context;
	}

	return sidtab_lookup_initial(s, SECINITSID_UNLABELED);
}

struct context *sidtab_search(struct sidtab *s, u32 sid)
{
	return sidtab_search_core(s, sid, 0);
}

struct context *sidtab_search_force(struct sidtab *s, u32 sid)
{
	return sidtab_search_core(s, sid, 1);
}

static int sidtab_find_context(union sidtab_entry_inner entry,
			       u32 *pos, u32 count, u32 level,
			       struct context *context, u32 *index)
{
	int rc;
	u32 i;

	if (level != 0) {
		struct sidtab_node_inner *node = entry.ptr_inner;

		i = 0;
		while (i < SIDTAB_INNER_ENTRIES && *pos < count) {
			rc = sidtab_find_context(node->entries[i],
						 pos, count, level - 1,
						 context, index);
			if (rc == 0)
				return 0;
			i++;
		}
	} else {
		struct sidtab_node_leaf *node = entry.ptr_leaf;

		i = 0;
		while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
			if (context_cmp(&node->entries[i].context, context)) {
				*index = *pos;
				return 0;
			}
			(*pos)++;
			i++;
		}
	}
	return -ENOENT;
}

static void sidtab_rcache_update(struct sidtab *s, u32 index, u32 pos)
{
	while (pos > 0) {
		WRITE_ONCE(s->rcache[pos], READ_ONCE(s->rcache[pos - 1]));
		--pos;
	}
	WRITE_ONCE(s->rcache[0], index);
}

static void sidtab_rcache_push(struct sidtab *s, u32 index)
{
	sidtab_rcache_update(s, index, SIDTAB_RCACHE_SIZE - 1);
}

static int sidtab_rcache_search(struct sidtab *s, struct context *context,
				u32 *index)
{
	u32 i;

	for (i = 0; i < SIDTAB_RCACHE_SIZE; i++) {
		u32 v = READ_ONCE(s->rcache[i]);

		if (v >= SIDTAB_MAX)
			continue;

		if (context_cmp(sidtab_do_lookup(s, v, 0), context)) {
			sidtab_rcache_update(s, v, i);
			*index = v;
			return 0;
		}
	}
	return -ENOENT;
}

static int sidtab_reverse_lookup(struct sidtab *s, struct context *context,
				 u32 *index)
{
	unsigned long flags;
	u32 count, count_locked, level, pos;
	struct sidtab_convert_params *convert;
	struct context *dst, *dst_convert;
	int rc;

	rc = sidtab_rcache_search(s, context, index);
	if (rc == 0)
		return 0;

	/* read entries only after reading count */
	count = smp_load_acquire(&s->count);
	level = sidtab_level_from_count(count);

	pos = 0;
	rc = sidtab_find_context(s->roots[level], &pos, count, level,
				 context, index);
	if (rc == 0) {
		sidtab_rcache_push(s, *index);
		return 0;
	}

	/* lock-free search failed: lock, re-search, and insert if not found */
	spin_lock_irqsave(&s->lock, flags);

	convert = s->convert;
	count_locked = s->count;
	level = sidtab_level_from_count(count_locked);

	/* if count has changed before we acquired the lock, then catch up */
	while (count < count_locked) {
		if (context_cmp(sidtab_do_lookup(s, count, 0), context)) {
			sidtab_rcache_push(s, count);
			*index = count;
			rc = 0;
			goto out_unlock;
		}
		++count;
	}

	/* bail out if we already reached max entries */
	rc = -EOVERFLOW;
	if (count >= SIDTAB_MAX)
		goto out_unlock;

	/* insert context into new entry */
	rc = -ENOMEM;
	dst = sidtab_do_lookup(s, count, 1);
	if (!dst)
		goto out_unlock;

	rc = context_cpy(dst, context);
	if (rc)
		goto out_unlock;

	/*
	 * if we are building a new sidtab, we need to convert the context
	 * and insert it there as well
	 */
	if (convert) {
		rc = -ENOMEM;
		dst_convert = sidtab_do_lookup(convert->target, count, 1);
		if (!dst_convert) {
			context_destroy(dst);
			goto out_unlock;
		}

		rc = convert->func(context, dst_convert, convert->args);
		if (rc) {
			context_destroy(dst);
			goto out_unlock;
		}

		/* at this point we know the insert won't fail */
		convert->target->count = count + 1;
	}

	if (context->len)
		pr_info("SELinux:  Context %s is not valid (left unmapped).\n",
			context->str);

	sidtab_rcache_push(s, count);
	*index = count;

	/* write entries before writing new count */
	smp_store_release(&s->count, count + 1);

	rc = 0;
out_unlock:
	spin_unlock_irqrestore(&s->lock, flags);
	return rc;
}

int sidtab_context_to_sid(struct sidtab *s, struct context *context, u32 *sid)
{
	int rc;
	u32 i;

	for (i = 0; i < SECINITSID_NUM; i++) {
		struct sidtab_isid_entry *entry = &s->isids[i];

		if (entry->set && context_cmp(context, &entry->context)) {
			*sid = i + 1;
			return 0;
		}
	}

	rc = sidtab_reverse_lookup(s, context, sid);
	if (rc)
		return rc;
	*sid += SECINITSID_NUM + 1;
	return 0;
}

static int sidtab_convert_tree(union sidtab_entry_inner *edst,
			       union sidtab_entry_inner *esrc,
			       u32 *pos, u32 count, u32 level,
			       struct sidtab_convert_params *convert)
{
	int rc;
	u32 i;

	if (level != 0) {
		if (!edst->ptr_inner) {
			edst->ptr_inner = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
						  GFP_KERNEL);
			if (!edst->ptr_inner)
				return -ENOMEM;
		}
		i = 0;
		while (i < SIDTAB_INNER_ENTRIES && *pos < count) {
			rc = sidtab_convert_tree(&edst->ptr_inner->entries[i],
						 &esrc->ptr_inner->entries[i],
						 pos, count, level - 1,
						 convert);
			if (rc)
				return rc;
			i++;
		}
	} else {
		if (!edst->ptr_leaf) {
			edst->ptr_leaf = kzalloc(SIDTAB_NODE_ALLOC_SIZE,
						 GFP_KERNEL);
			if (!edst->ptr_leaf)
				return -ENOMEM;
		}
		i = 0;
		while (i < SIDTAB_LEAF_ENTRIES && *pos < count) {
			rc = convert->func(&esrc->ptr_leaf->entries[i].context,
					   &edst->ptr_leaf->entries[i].context,
					   convert->args);
			if (rc)
				return rc;
			(*pos)++;
			i++;
		}
		cond_resched();
	}
	return 0;
}

int sidtab_convert(struct sidtab *s, struct sidtab_convert_params *params)
{
	unsigned long flags;
	u32 count, level, pos;
	int rc;

	spin_lock_irqsave(&s->lock, flags);

	/* concurrent policy loads are not allowed */
	if (s->convert) {
		spin_unlock_irqrestore(&s->lock, flags);
		return -EBUSY;
	}

	count = s->count;
	level = sidtab_level_from_count(count);

	/* allocate last leaf in the new sidtab (to avoid race with
	 * live convert)
	 */
	rc = sidtab_do_lookup(params->target, count - 1, 1) ? 0 : -ENOMEM;
	if (rc) {
		spin_unlock_irqrestore(&s->lock, flags);
		return rc;
	}

	/* set count in case no new entries are added during conversion */
	params->target->count = count;

	/* enable live convert of new entries */
	s->convert = params;

	/* we can safely do the rest of the conversion outside the lock */
	spin_unlock_irqrestore(&s->lock, flags);

	pr_info("SELinux:  Converting %u SID table entries...\n", count);

	/* convert all entries not covered by live convert */
	pos = 0;
	rc = sidtab_convert_tree(&params->target->roots[level],
				 &s->roots[level], &pos, count, level, params);
	if (rc) {
		/* we need to keep the old table - disable live convert */
		spin_lock_irqsave(&s->lock, flags);
		s->convert = NULL;
		spin_unlock_irqrestore(&s->lock, flags);
	}
	return rc;
}

static void sidtab_destroy_tree(union sidtab_entry_inner entry, u32 level)
{
	u32 i;

	if (level != 0) {
		struct sidtab_node_inner *node = entry.ptr_inner;

		if (!node)
			return;

		for (i = 0; i < SIDTAB_INNER_ENTRIES; i++)
			sidtab_destroy_tree(node->entries[i], level - 1);
		kfree(node);
	} else {
		struct sidtab_node_leaf *node = entry.ptr_leaf;

		if (!node)
			return;

		for (i = 0; i < SIDTAB_LEAF_ENTRIES; i++)
			context_destroy(&node->entries[i].context);
		kfree(node);
	}
}

void sidtab_destroy(struct sidtab *s)
{
	u32 i, level;

	for (i = 0; i < SECINITSID_NUM; i++)
		if (s->isids[i].set)
			context_destroy(&s->isids[i].context);

	level = SIDTAB_MAX_LEVEL;
	while (level && !s->roots[level].ptr_inner)
		--level;

	sidtab_destroy_tree(s->roots[level], level);
}