1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Test cases for KFENCE memory safety error detector. Since the interface with
4 * which KFENCE's reports are obtained is via the console, this is the output we
5 * should verify. For each test case checks the presence (or absence) of
6 * generated reports. Relies on 'console' tracepoint to capture reports as they
7 * appear in the kernel log.
8 *
9 * Copyright (C) 2020, Google LLC.
10 * Author: Alexander Potapenko <glider@google.com>
11 * Marco Elver <elver@google.com>
12 */
13
14#include <kunit/test.h>
15#include <linux/jiffies.h>
16#include <linux/kernel.h>
17#include <linux/kfence.h>
18#include <linux/mm.h>
19#include <linux/random.h>
20#include <linux/slab.h>
21#include <linux/spinlock.h>
22#include <linux/string.h>
23#include <linux/tracepoint.h>
24#include <trace/events/printk.h>
25
26#include <asm/kfence.h>
27
28#include "kfence.h"
29
30/* May be overridden by <asm/kfence.h>. */
31#ifndef arch_kfence_test_address
32#define arch_kfence_test_address(addr) (addr)
33#endif
34
35#define KFENCE_TEST_REQUIRES(test, cond) do { \
36 if (!(cond)) \
37 kunit_skip((test), "Test requires: " #cond); \
38} while (0)
39
40/* Report as observed from console. */
41static struct {
42 spinlock_t lock;
43 int nlines;
44 char lines[2][256];
45} observed = {
46 .lock = __SPIN_LOCK_UNLOCKED(observed.lock),
47};
48
49/* Probe for console output: obtains observed lines of interest. */
50static void probe_console(void *ignore, const char *buf, size_t len)
51{
52 unsigned long flags;
53 int nlines;
54
55 spin_lock_irqsave(&observed.lock, flags);
56 nlines = observed.nlines;
57
58 if (strnstr(buf, "BUG: KFENCE: ", len) && strnstr(buf, "test_", len)) {
59 /*
60 * KFENCE report and related to the test.
61 *
62 * The provided @buf is not NUL-terminated; copy no more than
63 * @len bytes and let strscpy() add the missing NUL-terminator.
64 */
65 strscpy(p: observed.lines[0], q: buf, min(len + 1, sizeof(observed.lines[0])));
66 nlines = 1;
67 } else if (nlines == 1 && (strnstr(buf, "at 0x", len) || strnstr(buf, "of 0x", len))) {
68 strscpy(p: observed.lines[nlines++], q: buf, min(len + 1, sizeof(observed.lines[0])));
69 }
70
71 WRITE_ONCE(observed.nlines, nlines); /* Publish new nlines. */
72 spin_unlock_irqrestore(lock: &observed.lock, flags);
73}
74
75/* Check if a report related to the test exists. */
76static bool report_available(void)
77{
78 return READ_ONCE(observed.nlines) == ARRAY_SIZE(observed.lines);
79}
80
81/* Information we expect in a report. */
82struct expect_report {
83 enum kfence_error_type type; /* The type or error. */
84 void *fn; /* Function pointer to expected function where access occurred. */
85 char *addr; /* Address at which the bad access occurred. */
86 bool is_write; /* Is access a write. */
87};
88
89static const char *get_access_type(const struct expect_report *r)
90{
91 return r->is_write ? "write" : "read";
92}
93
94/* Check observed report matches information in @r. */
95static bool report_matches(const struct expect_report *r)
96{
97 unsigned long addr = (unsigned long)r->addr;
98 bool ret = false;
99 unsigned long flags;
100 typeof(observed.lines) expect;
101 const char *end;
102 char *cur;
103
104 /* Doubled-checked locking. */
105 if (!report_available())
106 return false;
107
108 /* Generate expected report contents. */
109
110 /* Title */
111 cur = expect[0];
112 end = &expect[0][sizeof(expect[0]) - 1];
113 switch (r->type) {
114 case KFENCE_ERROR_OOB:
115 cur += scnprintf(buf: cur, size: end - cur, fmt: "BUG: KFENCE: out-of-bounds %s",
116 get_access_type(r));
117 break;
118 case KFENCE_ERROR_UAF:
119 cur += scnprintf(buf: cur, size: end - cur, fmt: "BUG: KFENCE: use-after-free %s",
120 get_access_type(r));
121 break;
122 case KFENCE_ERROR_CORRUPTION:
123 cur += scnprintf(buf: cur, size: end - cur, fmt: "BUG: KFENCE: memory corruption");
124 break;
125 case KFENCE_ERROR_INVALID:
126 cur += scnprintf(buf: cur, size: end - cur, fmt: "BUG: KFENCE: invalid %s",
127 get_access_type(r));
128 break;
129 case KFENCE_ERROR_INVALID_FREE:
130 cur += scnprintf(buf: cur, size: end - cur, fmt: "BUG: KFENCE: invalid free");
131 break;
132 }
133
134 scnprintf(buf: cur, size: end - cur, fmt: " in %pS", r->fn);
135 /* The exact offset won't match, remove it; also strip module name. */
136 cur = strchr(expect[0], '+');
137 if (cur)
138 *cur = '\0';
139
140 /* Access information */
141 cur = expect[1];
142 end = &expect[1][sizeof(expect[1]) - 1];
143
144 switch (r->type) {
145 case KFENCE_ERROR_OOB:
146 cur += scnprintf(buf: cur, size: end - cur, fmt: "Out-of-bounds %s at", get_access_type(r));
147 addr = arch_kfence_test_address(addr);
148 break;
149 case KFENCE_ERROR_UAF:
150 cur += scnprintf(buf: cur, size: end - cur, fmt: "Use-after-free %s at", get_access_type(r));
151 addr = arch_kfence_test_address(addr);
152 break;
153 case KFENCE_ERROR_CORRUPTION:
154 cur += scnprintf(buf: cur, size: end - cur, fmt: "Corrupted memory at");
155 break;
156 case KFENCE_ERROR_INVALID:
157 cur += scnprintf(buf: cur, size: end - cur, fmt: "Invalid %s at", get_access_type(r));
158 addr = arch_kfence_test_address(addr);
159 break;
160 case KFENCE_ERROR_INVALID_FREE:
161 cur += scnprintf(buf: cur, size: end - cur, fmt: "Invalid free of");
162 break;
163 }
164
165 cur += scnprintf(buf: cur, size: end - cur, fmt: " 0x%p", (void *)addr);
166
167 spin_lock_irqsave(&observed.lock, flags);
168 if (!report_available())
169 goto out; /* A new report is being captured. */
170
171 /* Finally match expected output to what we actually observed. */
172 ret = strstr(observed.lines[0], expect[0]) && strstr(observed.lines[1], expect[1]);
173out:
174 spin_unlock_irqrestore(lock: &observed.lock, flags);
175 return ret;
176}
177
178/* ===== Test cases ===== */
179
180#define TEST_PRIV_WANT_MEMCACHE ((void *)1)
181
182/* Cache used by tests; if NULL, allocate from kmalloc instead. */
183static struct kmem_cache *test_cache;
184
185static size_t setup_test_cache(struct kunit *test, size_t size, slab_flags_t flags,
186 void (*ctor)(void *))
187{
188 if (test->priv != TEST_PRIV_WANT_MEMCACHE)
189 return size;
190
191 kunit_info(test, "%s: size=%zu, ctor=%ps\n", __func__, size, ctor);
192
193 /*
194 * Use SLAB_NO_MERGE to prevent merging with existing caches.
195 * Use SLAB_ACCOUNT to allocate via memcg, if enabled.
196 */
197 flags |= SLAB_NO_MERGE | SLAB_ACCOUNT;
198 test_cache = kmem_cache_create(name: "test", size, align: 1, flags, ctor);
199 KUNIT_ASSERT_TRUE_MSG(test, test_cache, "could not create cache");
200
201 return size;
202}
203
204static void test_cache_destroy(void)
205{
206 if (!test_cache)
207 return;
208
209 kmem_cache_destroy(s: test_cache);
210 test_cache = NULL;
211}
212
213static inline size_t kmalloc_cache_alignment(size_t size)
214{
215 /* just to get ->align so no need to pass in the real caller */
216 enum kmalloc_cache_type type = kmalloc_type(GFP_KERNEL, caller: 0);
217 return kmalloc_caches[type][__kmalloc_index(size, size_is_constant: false)]->align;
218}
219
220/* Must always inline to match stack trace against caller. */
221static __always_inline void test_free(void *ptr)
222{
223 if (test_cache)
224 kmem_cache_free(s: test_cache, objp: ptr);
225 else
226 kfree(objp: ptr);
227}
228
229/*
230 * If this should be a KFENCE allocation, and on which side the allocation and
231 * the closest guard page should be.
232 */
233enum allocation_policy {
234 ALLOCATE_ANY, /* KFENCE, any side. */
235 ALLOCATE_LEFT, /* KFENCE, left side of page. */
236 ALLOCATE_RIGHT, /* KFENCE, right side of page. */
237 ALLOCATE_NONE, /* No KFENCE allocation. */
238};
239
240/*
241 * Try to get a guarded allocation from KFENCE. Uses either kmalloc() or the
242 * current test_cache if set up.
243 */
244static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocation_policy policy)
245{
246 void *alloc;
247 unsigned long timeout, resched_after;
248 const char *policy_name;
249
250 switch (policy) {
251 case ALLOCATE_ANY:
252 policy_name = "any";
253 break;
254 case ALLOCATE_LEFT:
255 policy_name = "left";
256 break;
257 case ALLOCATE_RIGHT:
258 policy_name = "right";
259 break;
260 case ALLOCATE_NONE:
261 policy_name = "none";
262 break;
263 }
264
265 kunit_info(test, "%s: size=%zu, gfp=%x, policy=%s, cache=%i\n", __func__, size, gfp,
266 policy_name, !!test_cache);
267
268 /*
269 * 100x the sample interval should be more than enough to ensure we get
270 * a KFENCE allocation eventually.
271 */
272 timeout = jiffies + msecs_to_jiffies(m: 100 * kfence_sample_interval);
273 /*
274 * Especially for non-preemption kernels, ensure the allocation-gate
275 * timer can catch up: after @resched_after, every failed allocation
276 * attempt yields, to ensure the allocation-gate timer is scheduled.
277 */
278 resched_after = jiffies + msecs_to_jiffies(m: kfence_sample_interval);
279 do {
280 if (test_cache)
281 alloc = kmem_cache_alloc(cachep: test_cache, flags: gfp);
282 else
283 alloc = kmalloc(size, flags: gfp);
284
285 if (is_kfence_address(addr: alloc)) {
286 struct slab *slab = virt_to_slab(addr: alloc);
287 enum kmalloc_cache_type type = kmalloc_type(GFP_KERNEL, _RET_IP_);
288 struct kmem_cache *s = test_cache ?:
289 kmalloc_caches[type][__kmalloc_index(size, size_is_constant: false)];
290
291 /*
292 * Verify that various helpers return the right values
293 * even for KFENCE objects; these are required so that
294 * memcg accounting works correctly.
295 */
296 KUNIT_EXPECT_EQ(test, obj_to_index(s, slab, alloc), 0U);
297 KUNIT_EXPECT_EQ(test, objs_per_slab(s, slab), 1);
298
299 if (policy == ALLOCATE_ANY)
300 return alloc;
301 if (policy == ALLOCATE_LEFT && PAGE_ALIGNED(alloc))
302 return alloc;
303 if (policy == ALLOCATE_RIGHT && !PAGE_ALIGNED(alloc))
304 return alloc;
305 } else if (policy == ALLOCATE_NONE)
306 return alloc;
307
308 test_free(ptr: alloc);
309
310 if (time_after(jiffies, resched_after))
311 cond_resched();
312 } while (time_before(jiffies, timeout));
313
314 KUNIT_ASSERT_TRUE_MSG(test, false, "failed to allocate from KFENCE");
315 return NULL; /* Unreachable. */
316}
317
318static void test_out_of_bounds_read(struct kunit *test)
319{
320 size_t size = 32;
321 struct expect_report expect = {
322 .type = KFENCE_ERROR_OOB,
323 .fn = test_out_of_bounds_read,
324 .is_write = false,
325 };
326 char *buf;
327
328 setup_test_cache(test, size, flags: 0, NULL);
329
330 /*
331 * If we don't have our own cache, adjust based on alignment, so that we
332 * actually access guard pages on either side.
333 */
334 if (!test_cache)
335 size = kmalloc_cache_alignment(size);
336
337 /* Test both sides. */
338
339 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_LEFT);
340 expect.addr = buf - 1;
341 READ_ONCE(*expect.addr);
342 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
343 test_free(ptr: buf);
344
345 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_RIGHT);
346 expect.addr = buf + size;
347 READ_ONCE(*expect.addr);
348 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
349 test_free(ptr: buf);
350}
351
352static void test_out_of_bounds_write(struct kunit *test)
353{
354 size_t size = 32;
355 struct expect_report expect = {
356 .type = KFENCE_ERROR_OOB,
357 .fn = test_out_of_bounds_write,
358 .is_write = true,
359 };
360 char *buf;
361
362 setup_test_cache(test, size, flags: 0, NULL);
363 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_LEFT);
364 expect.addr = buf - 1;
365 WRITE_ONCE(*expect.addr, 42);
366 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
367 test_free(ptr: buf);
368}
369
370static void test_use_after_free_read(struct kunit *test)
371{
372 const size_t size = 32;
373 struct expect_report expect = {
374 .type = KFENCE_ERROR_UAF,
375 .fn = test_use_after_free_read,
376 .is_write = false,
377 };
378
379 setup_test_cache(test, size, flags: 0, NULL);
380 expect.addr = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY);
381 test_free(ptr: expect.addr);
382 READ_ONCE(*expect.addr);
383 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
384}
385
386static void test_double_free(struct kunit *test)
387{
388 const size_t size = 32;
389 struct expect_report expect = {
390 .type = KFENCE_ERROR_INVALID_FREE,
391 .fn = test_double_free,
392 };
393
394 setup_test_cache(test, size, flags: 0, NULL);
395 expect.addr = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY);
396 test_free(ptr: expect.addr);
397 test_free(ptr: expect.addr); /* Double-free. */
398 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
399}
400
401static void test_invalid_addr_free(struct kunit *test)
402{
403 const size_t size = 32;
404 struct expect_report expect = {
405 .type = KFENCE_ERROR_INVALID_FREE,
406 .fn = test_invalid_addr_free,
407 };
408 char *buf;
409
410 setup_test_cache(test, size, flags: 0, NULL);
411 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY);
412 expect.addr = buf + 1; /* Free on invalid address. */
413 test_free(ptr: expect.addr); /* Invalid address free. */
414 test_free(ptr: buf); /* No error. */
415 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
416}
417
418static void test_corruption(struct kunit *test)
419{
420 size_t size = 32;
421 struct expect_report expect = {
422 .type = KFENCE_ERROR_CORRUPTION,
423 .fn = test_corruption,
424 };
425 char *buf;
426
427 setup_test_cache(test, size, flags: 0, NULL);
428
429 /* Test both sides. */
430
431 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_LEFT);
432 expect.addr = buf + size;
433 WRITE_ONCE(*expect.addr, 42);
434 test_free(ptr: buf);
435 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
436
437 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_RIGHT);
438 expect.addr = buf - 1;
439 WRITE_ONCE(*expect.addr, 42);
440 test_free(ptr: buf);
441 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
442}
443
444/*
445 * KFENCE is unable to detect an OOB if the allocation's alignment requirements
446 * leave a gap between the object and the guard page. Specifically, an
447 * allocation of e.g. 73 bytes is aligned on 8 and 128 bytes for SLUB or SLAB
448 * respectively. Therefore it is impossible for the allocated object to
449 * contiguously line up with the right guard page.
450 *
451 * However, we test that an access to memory beyond the gap results in KFENCE
452 * detecting an OOB access.
453 */
454static void test_kmalloc_aligned_oob_read(struct kunit *test)
455{
456 const size_t size = 73;
457 const size_t align = kmalloc_cache_alignment(size);
458 struct expect_report expect = {
459 .type = KFENCE_ERROR_OOB,
460 .fn = test_kmalloc_aligned_oob_read,
461 .is_write = false,
462 };
463 char *buf;
464
465 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_RIGHT);
466
467 /*
468 * The object is offset to the right, so there won't be an OOB to the
469 * left of it.
470 */
471 READ_ONCE(*(buf - 1));
472 KUNIT_EXPECT_FALSE(test, report_available());
473
474 /*
475 * @buf must be aligned on @align, therefore buf + size belongs to the
476 * same page -> no OOB.
477 */
478 READ_ONCE(*(buf + size));
479 KUNIT_EXPECT_FALSE(test, report_available());
480
481 /* Overflowing by @align bytes will result in an OOB. */
482 expect.addr = buf + size + align;
483 READ_ONCE(*expect.addr);
484 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
485
486 test_free(ptr: buf);
487}
488
489static void test_kmalloc_aligned_oob_write(struct kunit *test)
490{
491 const size_t size = 73;
492 struct expect_report expect = {
493 .type = KFENCE_ERROR_CORRUPTION,
494 .fn = test_kmalloc_aligned_oob_write,
495 };
496 char *buf;
497
498 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_RIGHT);
499 /*
500 * The object is offset to the right, so we won't get a page
501 * fault immediately after it.
502 */
503 expect.addr = buf + size;
504 WRITE_ONCE(*expect.addr, READ_ONCE(*expect.addr) + 1);
505 KUNIT_EXPECT_FALSE(test, report_available());
506 test_free(ptr: buf);
507 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
508}
509
510/* Test cache shrinking and destroying with KFENCE. */
511static void test_shrink_memcache(struct kunit *test)
512{
513 const size_t size = 32;
514 void *buf;
515
516 setup_test_cache(test, size, flags: 0, NULL);
517 KUNIT_EXPECT_TRUE(test, test_cache);
518 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY);
519 kmem_cache_shrink(s: test_cache);
520 test_free(ptr: buf);
521
522 KUNIT_EXPECT_FALSE(test, report_available());
523}
524
525static void ctor_set_x(void *obj)
526{
527 /* Every object has at least 8 bytes. */
528 memset(obj, 'x', 8);
529}
530
531/* Ensure that SL*B does not modify KFENCE objects on bulk free. */
532static void test_free_bulk(struct kunit *test)
533{
534 int iter;
535
536 for (iter = 0; iter < 5; iter++) {
537 const size_t size = setup_test_cache(test, size: get_random_u32_inclusive(floor: 8, ceil: 307),
538 flags: 0, ctor: (iter & 1) ? ctor_set_x : NULL);
539 void *objects[] = {
540 test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_RIGHT),
541 test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_NONE),
542 test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_LEFT),
543 test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_NONE),
544 test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_NONE),
545 };
546
547 kmem_cache_free_bulk(s: test_cache, ARRAY_SIZE(objects), p: objects);
548 KUNIT_ASSERT_FALSE(test, report_available());
549 test_cache_destroy();
550 }
551}
552
553/* Test init-on-free works. */
554static void test_init_on_free(struct kunit *test)
555{
556 const size_t size = 32;
557 struct expect_report expect = {
558 .type = KFENCE_ERROR_UAF,
559 .fn = test_init_on_free,
560 .is_write = false,
561 };
562 int i;
563
564 KFENCE_TEST_REQUIRES(test, IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON));
565 /* Assume it hasn't been disabled on command line. */
566
567 setup_test_cache(test, size, flags: 0, NULL);
568 expect.addr = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY);
569 for (i = 0; i < size; i++)
570 expect.addr[i] = i + 1;
571 test_free(ptr: expect.addr);
572
573 for (i = 0; i < size; i++) {
574 /*
575 * This may fail if the page was recycled by KFENCE and then
576 * written to again -- this however, is near impossible with a
577 * default config.
578 */
579 KUNIT_EXPECT_EQ(test, expect.addr[i], (char)0);
580
581 if (!i) /* Only check first access to not fail test if page is ever re-protected. */
582 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
583 }
584}
585
586/* Ensure that constructors work properly. */
587static void test_memcache_ctor(struct kunit *test)
588{
589 const size_t size = 32;
590 char *buf;
591 int i;
592
593 setup_test_cache(test, size, flags: 0, ctor: ctor_set_x);
594 buf = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY);
595
596 for (i = 0; i < 8; i++)
597 KUNIT_EXPECT_EQ(test, buf[i], (char)'x');
598
599 test_free(ptr: buf);
600
601 KUNIT_EXPECT_FALSE(test, report_available());
602}
603
604/* Test that memory is zeroed if requested. */
605static void test_gfpzero(struct kunit *test)
606{
607 const size_t size = PAGE_SIZE; /* PAGE_SIZE so we can use ALLOCATE_ANY. */
608 char *buf1, *buf2;
609 int i;
610
611 /* Skip if we think it'd take too long. */
612 KFENCE_TEST_REQUIRES(test, kfence_sample_interval <= 100);
613
614 setup_test_cache(test, size, flags: 0, NULL);
615 buf1 = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY);
616 for (i = 0; i < size; i++)
617 buf1[i] = i + 1;
618 test_free(ptr: buf1);
619
620 /* Try to get same address again -- this can take a while. */
621 for (i = 0;; i++) {
622 buf2 = test_alloc(test, size, GFP_KERNEL | __GFP_ZERO, policy: ALLOCATE_ANY);
623 if (buf1 == buf2)
624 break;
625 test_free(ptr: buf2);
626
627 if (kthread_should_stop() || (i == CONFIG_KFENCE_NUM_OBJECTS)) {
628 kunit_warn(test, "giving up ... cannot get same object back\n");
629 return;
630 }
631 cond_resched();
632 }
633
634 for (i = 0; i < size; i++)
635 KUNIT_EXPECT_EQ(test, buf2[i], (char)0);
636
637 test_free(ptr: buf2);
638
639 KUNIT_EXPECT_FALSE(test, report_available());
640}
641
642static void test_invalid_access(struct kunit *test)
643{
644 const struct expect_report expect = {
645 .type = KFENCE_ERROR_INVALID,
646 .fn = test_invalid_access,
647 .addr = &__kfence_pool[10],
648 .is_write = false,
649 };
650
651 READ_ONCE(__kfence_pool[10]);
652 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
653}
654
655/* Test SLAB_TYPESAFE_BY_RCU works. */
656static void test_memcache_typesafe_by_rcu(struct kunit *test)
657{
658 const size_t size = 32;
659 struct expect_report expect = {
660 .type = KFENCE_ERROR_UAF,
661 .fn = test_memcache_typesafe_by_rcu,
662 .is_write = false,
663 };
664
665 setup_test_cache(test, size, SLAB_TYPESAFE_BY_RCU, NULL);
666 KUNIT_EXPECT_TRUE(test, test_cache); /* Want memcache. */
667
668 expect.addr = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY);
669 *expect.addr = 42;
670
671 rcu_read_lock();
672 test_free(ptr: expect.addr);
673 KUNIT_EXPECT_EQ(test, *expect.addr, (char)42);
674 /*
675 * Up to this point, memory should not have been freed yet, and
676 * therefore there should be no KFENCE report from the above access.
677 */
678 rcu_read_unlock();
679
680 /* Above access to @expect.addr should not have generated a report! */
681 KUNIT_EXPECT_FALSE(test, report_available());
682
683 /* Only after rcu_barrier() is the memory guaranteed to be freed. */
684 rcu_barrier();
685
686 /* Expect use-after-free. */
687 KUNIT_EXPECT_EQ(test, *expect.addr, (char)42);
688 KUNIT_EXPECT_TRUE(test, report_matches(&expect));
689}
690
691/* Test krealloc(). */
692static void test_krealloc(struct kunit *test)
693{
694 const size_t size = 32;
695 const struct expect_report expect = {
696 .type = KFENCE_ERROR_UAF,
697 .fn = test_krealloc,
698 .addr = test_alloc(test, size, GFP_KERNEL, policy: ALLOCATE_ANY),
699 .is_write = false,
700 };
701 char *buf = expect.addr;
702 int i;
703
704 KUNIT_EXPECT_FALSE(test, test_cache);
705 KUNIT_EXPECT_EQ(test, ksize(buf), size); /* Precise size match after KFENCE alloc. */
706 for (i = 0; i < size; i++)
707 buf[i] = i + 1;
708
709 /* Check that we successfully change the size. */
710 buf = krealloc(objp: buf, new_size: size * 3, GFP_KERNEL); /* Grow. */
711 /* Note: Might no longer be a KFENCE alloc. */
712 KUNIT_EXPECT_GE(test, ksize(buf), size * 3);
713 for (i = 0; i < size; i++)
714 KUNIT_EXPECT_EQ(test, buf[i], (char)(i + 1));
715 for (; i < size * 3; i++) /* Fill to extra bytes. */
716 buf[i] = i + 1;
717
718 buf = krealloc(objp: buf, new_size: size * 2, GFP_KERNEL); /* Shrink. */
719 KUNIT_EXPECT_GE(test, ksize(buf), size * 2);
720 for (i = 0; i < size * 2; i++)
721 KUNIT_EXPECT_EQ(test, buf[i], (char)(i + 1));
722
723 buf = krealloc(objp: buf, new_size: 0, GFP_KERNEL); /* Free. */
724 KUNIT_EXPECT_EQ(test, (unsigned long)buf, (unsigned long)ZERO_SIZE_PTR);
725 KUNIT_ASSERT_FALSE(test, report_available()); /* No reports yet! */
726
727 READ_ONCE(*expect.addr); /* Ensure krealloc() actually freed earlier KFENCE object. */
728 KUNIT_ASSERT_TRUE(test, report_matches(&expect));
729}
730
731/* Test that some objects from a bulk allocation belong to KFENCE pool. */
732static void test_memcache_alloc_bulk(struct kunit *test)
733{
734 const size_t size = 32;
735 bool pass = false;
736 unsigned long timeout;
737
738 setup_test_cache(test, size, flags: 0, NULL);
739 KUNIT_EXPECT_TRUE(test, test_cache); /* Want memcache. */
740 /*
741 * 100x the sample interval should be more than enough to ensure we get
742 * a KFENCE allocation eventually.
743 */
744 timeout = jiffies + msecs_to_jiffies(m: 100 * kfence_sample_interval);
745 do {
746 void *objects[100];
747 int i, num = kmem_cache_alloc_bulk(s: test_cache, GFP_ATOMIC, ARRAY_SIZE(objects),
748 p: objects);
749 if (!num)
750 continue;
751 for (i = 0; i < ARRAY_SIZE(objects); i++) {
752 if (is_kfence_address(addr: objects[i])) {
753 pass = true;
754 break;
755 }
756 }
757 kmem_cache_free_bulk(s: test_cache, size: num, p: objects);
758 /*
759 * kmem_cache_alloc_bulk() disables interrupts, and calling it
760 * in a tight loop may not give KFENCE a chance to switch the
761 * static branch. Call cond_resched() to let KFENCE chime in.
762 */
763 cond_resched();
764 } while (!pass && time_before(jiffies, timeout));
765
766 KUNIT_EXPECT_TRUE(test, pass);
767 KUNIT_EXPECT_FALSE(test, report_available());
768}
769
770/*
771 * KUnit does not provide a way to provide arguments to tests, and we encode
772 * additional info in the name. Set up 2 tests per test case, one using the
773 * default allocator, and another using a custom memcache (suffix '-memcache').
774 */
775#define KFENCE_KUNIT_CASE(test_name) \
776 { .run_case = test_name, .name = #test_name }, \
777 { .run_case = test_name, .name = #test_name "-memcache" }
778
779static struct kunit_case kfence_test_cases[] = {
780 KFENCE_KUNIT_CASE(test_out_of_bounds_read),
781 KFENCE_KUNIT_CASE(test_out_of_bounds_write),
782 KFENCE_KUNIT_CASE(test_use_after_free_read),
783 KFENCE_KUNIT_CASE(test_double_free),
784 KFENCE_KUNIT_CASE(test_invalid_addr_free),
785 KFENCE_KUNIT_CASE(test_corruption),
786 KFENCE_KUNIT_CASE(test_free_bulk),
787 KFENCE_KUNIT_CASE(test_init_on_free),
788 KUNIT_CASE(test_kmalloc_aligned_oob_read),
789 KUNIT_CASE(test_kmalloc_aligned_oob_write),
790 KUNIT_CASE(test_shrink_memcache),
791 KUNIT_CASE(test_memcache_ctor),
792 KUNIT_CASE(test_invalid_access),
793 KUNIT_CASE(test_gfpzero),
794 KUNIT_CASE(test_memcache_typesafe_by_rcu),
795 KUNIT_CASE(test_krealloc),
796 KUNIT_CASE(test_memcache_alloc_bulk),
797 {},
798};
799
800/* ===== End test cases ===== */
801
802static int test_init(struct kunit *test)
803{
804 unsigned long flags;
805 int i;
806
807 if (!__kfence_pool)
808 return -EINVAL;
809
810 spin_lock_irqsave(&observed.lock, flags);
811 for (i = 0; i < ARRAY_SIZE(observed.lines); i++)
812 observed.lines[i][0] = '\0';
813 observed.nlines = 0;
814 spin_unlock_irqrestore(lock: &observed.lock, flags);
815
816 /* Any test with 'memcache' in its name will want a memcache. */
817 if (strstr(test->name, "memcache"))
818 test->priv = TEST_PRIV_WANT_MEMCACHE;
819 else
820 test->priv = NULL;
821
822 return 0;
823}
824
825static void test_exit(struct kunit *test)
826{
827 test_cache_destroy();
828}
829
830static int kfence_suite_init(struct kunit_suite *suite)
831{
832 register_trace_console(probe: probe_console, NULL);
833 return 0;
834}
835
836static void kfence_suite_exit(struct kunit_suite *suite)
837{
838 unregister_trace_console(probe: probe_console, NULL);
839 tracepoint_synchronize_unregister();
840}
841
842static struct kunit_suite kfence_test_suite = {
843 .name = "kfence",
844 .test_cases = kfence_test_cases,
845 .init = test_init,
846 .exit = test_exit,
847 .suite_init = kfence_suite_init,
848 .suite_exit = kfence_suite_exit,
849};
850
851kunit_test_suites(&kfence_test_suite);
852
853MODULE_LICENSE("GPL v2");
854MODULE_AUTHOR("Alexander Potapenko <glider@google.com>, Marco Elver <elver@google.com>");
855

source code of linux/mm/kfence/kfence_test.c