linux-stable/mm/kfence/kfence_test.c
GONG, Ruiqi 3c61529405 Randomized slab caches for kmalloc()
When exploiting memory vulnerabilities, "heap spraying" is a common
technique targeting those related to dynamic memory allocation (i.e. the
"heap"), and it plays an important role in a successful exploitation.
Basically, it is to overwrite the memory area of vulnerable object by
triggering allocation in other subsystems or modules and therefore
getting a reference to the targeted memory location. It's usable on
various types of vulnerablity including use after free (UAF), heap out-
of-bound write and etc.

There are (at least) two reasons why the heap can be sprayed: 1) generic
slab caches are shared among different subsystems and modules, and
2) dedicated slab caches could be merged with the generic ones.
Currently these two factors cannot be prevented at a low cost: the first
one is a widely used memory allocation mechanism, and shutting down slab
merging completely via `slub_nomerge` would be overkill.

To efficiently prevent heap spraying, we propose the following approach:
to create multiple copies of generic slab caches that will never be
merged, and random one of them will be used at allocation. The random
selection is based on the address of code that calls `kmalloc()`, which
means it is static at runtime (rather than dynamically determined at
each time of allocation, which could be bypassed by repeatedly spraying
in brute force). In other words, the randomness of cache selection will
be with respect to the code address rather than time, i.e. allocations
in different code paths would most likely pick different caches,
although kmalloc() at each place would use the same cache copy whenever
it is executed. In this way, the vulnerable object and memory allocated
in other subsystems and modules will (most probably) be on different
slab caches, which prevents the object from being sprayed.

Meanwhile, the static random selection is further enhanced with a
per-boot random seed, which prevents the attacker from finding a usable
kmalloc that happens to pick the same cache with the vulnerable
subsystem/module by analyzing the open source code. In other words, with
the per-boot seed, the random selection is static during each time the
system starts and runs, but not across different system startups.

The overhead of performance has been tested on a 40-core x86 server by
comparing the results of `perf bench all` between the kernels with and
without this patch based on the latest linux-next kernel, which shows
minor difference. A subset of benchmarks are listed below:

                sched/  sched/  syscall/       mem/       mem/
             messaging    pipe     basic     memcpy     memset
                 (sec)   (sec)     (sec)   (GB/sec)   (GB/sec)

control1         0.019   5.459     0.733  15.258789  51.398026
control2         0.019   5.439     0.730  16.009221  48.828125
control3         0.019   5.282     0.735  16.009221  48.828125
control_avg      0.019   5.393     0.733  15.759077  49.684759

experiment1      0.019   5.374     0.741  15.500992  46.502976
experiment2      0.019   5.440     0.746  16.276042  51.398026
experiment3      0.019   5.242     0.752  15.258789  51.398026
experiment_avg   0.019   5.352     0.746  15.678608  49.766343

The overhead of memory usage was measured by executing `free` after boot
on a QEMU VM with 1GB total memory, and as expected, it's positively
correlated with # of cache copies:

           control  4 copies  8 copies  16 copies

total       969.8M    968.2M    968.2M     968.2M
used         20.0M     21.9M     24.1M      26.7M
free        936.9M    933.6M    931.4M     928.6M
available   932.2M    928.8M    926.6M     923.9M

Co-developed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: GONG, Ruiqi <gongruiqi@huaweicloud.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: Dennis Zhou <dennis@kernel.org> # percpu
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
2023-07-18 10:07:47 +02:00

854 lines
23 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Test cases for KFENCE memory safety error detector. Since the interface with
* which KFENCE's reports are obtained is via the console, this is the output we
* should verify. For each test case checks the presence (or absence) of
* generated reports. Relies on 'console' tracepoint to capture reports as they
* appear in the kernel log.
*
* Copyright (C) 2020, Google LLC.
* Author: Alexander Potapenko <glider@google.com>
* Marco Elver <elver@google.com>
*/
#include <kunit/test.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/kfence.h>
#include <linux/mm.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/tracepoint.h>
#include <trace/events/printk.h>
#include <asm/kfence.h>
#include "kfence.h"
/* May be overridden by <asm/kfence.h>. */
#ifndef arch_kfence_test_address
#define arch_kfence_test_address(addr) (addr)
#endif
#define KFENCE_TEST_REQUIRES(test, cond) do { \
if (!(cond)) \
kunit_skip((test), "Test requires: " #cond); \
} while (0)
/* Report as observed from console. */
static struct {
spinlock_t lock;
int nlines;
char lines[2][256];
} observed = {
.lock = __SPIN_LOCK_UNLOCKED(observed.lock),
};
/* Probe for console output: obtains observed lines of interest. */
static void probe_console(void *ignore, const char *buf, size_t len)
{
unsigned long flags;
int nlines;
spin_lock_irqsave(&observed.lock, flags);
nlines = observed.nlines;
if (strnstr(buf, "BUG: KFENCE: ", len) && strnstr(buf, "test_", len)) {
/*
* KFENCE report and related to the test.
*
* The provided @buf is not NUL-terminated; copy no more than
* @len bytes and let strscpy() add the missing NUL-terminator.
*/
strscpy(observed.lines[0], buf, min(len + 1, sizeof(observed.lines[0])));
nlines = 1;
} else if (nlines == 1 && (strnstr(buf, "at 0x", len) || strnstr(buf, "of 0x", len))) {
strscpy(observed.lines[nlines++], buf, min(len + 1, sizeof(observed.lines[0])));
}
WRITE_ONCE(observed.nlines, nlines); /* Publish new nlines. */
spin_unlock_irqrestore(&observed.lock, flags);
}
/* Check if a report related to the test exists. */
static bool report_available(void)
{
return READ_ONCE(observed.nlines) == ARRAY_SIZE(observed.lines);
}
/* Information we expect in a report. */
struct expect_report {
enum kfence_error_type type; /* The type or error. */
void *fn; /* Function pointer to expected function where access occurred. */
char *addr; /* Address at which the bad access occurred. */
bool is_write; /* Is access a write. */
};
static const char *get_access_type(const struct expect_report *r)
{
return r->is_write ? "write" : "read";
}
/* Check observed report matches information in @r. */
static bool report_matches(const struct expect_report *r)
{
unsigned long addr = (unsigned long)r->addr;
bool ret = false;
unsigned long flags;
typeof(observed.lines) expect;
const char *end;
char *cur;
/* Doubled-checked locking. */
if (!report_available())
return false;
/* Generate expected report contents. */
/* Title */
cur = expect[0];
end = &expect[0][sizeof(expect[0]) - 1];
switch (r->type) {
case KFENCE_ERROR_OOB:
cur += scnprintf(cur, end - cur, "BUG: KFENCE: out-of-bounds %s",
get_access_type(r));
break;
case KFENCE_ERROR_UAF:
cur += scnprintf(cur, end - cur, "BUG: KFENCE: use-after-free %s",
get_access_type(r));
break;
case KFENCE_ERROR_CORRUPTION:
cur += scnprintf(cur, end - cur, "BUG: KFENCE: memory corruption");
break;
case KFENCE_ERROR_INVALID:
cur += scnprintf(cur, end - cur, "BUG: KFENCE: invalid %s",
get_access_type(r));
break;
case KFENCE_ERROR_INVALID_FREE:
cur += scnprintf(cur, end - cur, "BUG: KFENCE: invalid free");
break;
}
scnprintf(cur, end - cur, " in %pS", r->fn);
/* The exact offset won't match, remove it; also strip module name. */
cur = strchr(expect[0], '+');
if (cur)
*cur = '\0';
/* Access information */
cur = expect[1];
end = &expect[1][sizeof(expect[1]) - 1];
switch (r->type) {
case KFENCE_ERROR_OOB:
cur += scnprintf(cur, end - cur, "Out-of-bounds %s at", get_access_type(r));
addr = arch_kfence_test_address(addr);
break;
case KFENCE_ERROR_UAF:
cur += scnprintf(cur, end - cur, "Use-after-free %s at", get_access_type(r));
addr = arch_kfence_test_address(addr);
break;
case KFENCE_ERROR_CORRUPTION:
cur += scnprintf(cur, end - cur, "Corrupted memory at");
break;
case KFENCE_ERROR_INVALID:
cur += scnprintf(cur, end - cur, "Invalid %s at", get_access_type(r));
addr = arch_kfence_test_address(addr);
break;
case KFENCE_ERROR_INVALID_FREE:
cur += scnprintf(cur, end - cur, "Invalid free of");
break;
}
cur += scnprintf(cur, end - cur, " 0x%p", (void *)addr);
spin_lock_irqsave(&observed.lock, flags);
if (!report_available())
goto out; /* A new report is being captured. */
/* Finally match expected output to what we actually observed. */
ret = strstr(observed.lines[0], expect[0]) && strstr(observed.lines[1], expect[1]);
out:
spin_unlock_irqrestore(&observed.lock, flags);
return ret;
}
/* ===== Test cases ===== */
#define TEST_PRIV_WANT_MEMCACHE ((void *)1)
/* Cache used by tests; if NULL, allocate from kmalloc instead. */
static struct kmem_cache *test_cache;
static size_t setup_test_cache(struct kunit *test, size_t size, slab_flags_t flags,
void (*ctor)(void *))
{
if (test->priv != TEST_PRIV_WANT_MEMCACHE)
return size;
kunit_info(test, "%s: size=%zu, ctor=%ps\n", __func__, size, ctor);
/*
* Use SLAB_NO_MERGE to prevent merging with existing caches.
* Use SLAB_ACCOUNT to allocate via memcg, if enabled.
*/
flags |= SLAB_NO_MERGE | SLAB_ACCOUNT;
test_cache = kmem_cache_create("test", size, 1, flags, ctor);
KUNIT_ASSERT_TRUE_MSG(test, test_cache, "could not create cache");
return size;
}
static void test_cache_destroy(void)
{
if (!test_cache)
return;
kmem_cache_destroy(test_cache);
test_cache = NULL;
}
static inline size_t kmalloc_cache_alignment(size_t size)
{
/* just to get ->align so no need to pass in the real caller */
enum kmalloc_cache_type type = kmalloc_type(GFP_KERNEL, 0);
return kmalloc_caches[type][__kmalloc_index(size, false)]->align;
}
/* Must always inline to match stack trace against caller. */
static __always_inline void test_free(void *ptr)
{
if (test_cache)
kmem_cache_free(test_cache, ptr);
else
kfree(ptr);
}
/*
* If this should be a KFENCE allocation, and on which side the allocation and
* the closest guard page should be.
*/
enum allocation_policy {
ALLOCATE_ANY, /* KFENCE, any side. */
ALLOCATE_LEFT, /* KFENCE, left side of page. */
ALLOCATE_RIGHT, /* KFENCE, right side of page. */
ALLOCATE_NONE, /* No KFENCE allocation. */
};
/*
* Try to get a guarded allocation from KFENCE. Uses either kmalloc() or the
* current test_cache if set up.
*/
static void *test_alloc(struct kunit *test, size_t size, gfp_t gfp, enum allocation_policy policy)
{
void *alloc;
unsigned long timeout, resched_after;
const char *policy_name;
switch (policy) {
case ALLOCATE_ANY:
policy_name = "any";
break;
case ALLOCATE_LEFT:
policy_name = "left";
break;
case ALLOCATE_RIGHT:
policy_name = "right";
break;
case ALLOCATE_NONE:
policy_name = "none";
break;
}
kunit_info(test, "%s: size=%zu, gfp=%x, policy=%s, cache=%i\n", __func__, size, gfp,
policy_name, !!test_cache);
/*
* 100x the sample interval should be more than enough to ensure we get
* a KFENCE allocation eventually.
*/
timeout = jiffies + msecs_to_jiffies(100 * kfence_sample_interval);
/*
* Especially for non-preemption kernels, ensure the allocation-gate
* timer can catch up: after @resched_after, every failed allocation
* attempt yields, to ensure the allocation-gate timer is scheduled.
*/
resched_after = jiffies + msecs_to_jiffies(kfence_sample_interval);
do {
if (test_cache)
alloc = kmem_cache_alloc(test_cache, gfp);
else
alloc = kmalloc(size, gfp);
if (is_kfence_address(alloc)) {
struct slab *slab = virt_to_slab(alloc);
enum kmalloc_cache_type type = kmalloc_type(GFP_KERNEL, _RET_IP_);
struct kmem_cache *s = test_cache ?:
kmalloc_caches[type][__kmalloc_index(size, false)];
/*
* Verify that various helpers return the right values
* even for KFENCE objects; these are required so that
* memcg accounting works correctly.
*/
KUNIT_EXPECT_EQ(test, obj_to_index(s, slab, alloc), 0U);
KUNIT_EXPECT_EQ(test, objs_per_slab(s, slab), 1);
if (policy == ALLOCATE_ANY)
return alloc;
if (policy == ALLOCATE_LEFT && PAGE_ALIGNED(alloc))
return alloc;
if (policy == ALLOCATE_RIGHT && !PAGE_ALIGNED(alloc))
return alloc;
} else if (policy == ALLOCATE_NONE)
return alloc;
test_free(alloc);
if (time_after(jiffies, resched_after))
cond_resched();
} while (time_before(jiffies, timeout));
KUNIT_ASSERT_TRUE_MSG(test, false, "failed to allocate from KFENCE");
return NULL; /* Unreachable. */
}
static void test_out_of_bounds_read(struct kunit *test)
{
size_t size = 32;
struct expect_report expect = {
.type = KFENCE_ERROR_OOB,
.fn = test_out_of_bounds_read,
.is_write = false,
};
char *buf;
setup_test_cache(test, size, 0, NULL);
/*
* If we don't have our own cache, adjust based on alignment, so that we
* actually access guard pages on either side.
*/
if (!test_cache)
size = kmalloc_cache_alignment(size);
/* Test both sides. */
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_LEFT);
expect.addr = buf - 1;
READ_ONCE(*expect.addr);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
test_free(buf);
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_RIGHT);
expect.addr = buf + size;
READ_ONCE(*expect.addr);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
test_free(buf);
}
static void test_out_of_bounds_write(struct kunit *test)
{
size_t size = 32;
struct expect_report expect = {
.type = KFENCE_ERROR_OOB,
.fn = test_out_of_bounds_write,
.is_write = true,
};
char *buf;
setup_test_cache(test, size, 0, NULL);
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_LEFT);
expect.addr = buf - 1;
WRITE_ONCE(*expect.addr, 42);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
test_free(buf);
}
static void test_use_after_free_read(struct kunit *test)
{
const size_t size = 32;
struct expect_report expect = {
.type = KFENCE_ERROR_UAF,
.fn = test_use_after_free_read,
.is_write = false,
};
setup_test_cache(test, size, 0, NULL);
expect.addr = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
test_free(expect.addr);
READ_ONCE(*expect.addr);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
static void test_double_free(struct kunit *test)
{
const size_t size = 32;
struct expect_report expect = {
.type = KFENCE_ERROR_INVALID_FREE,
.fn = test_double_free,
};
setup_test_cache(test, size, 0, NULL);
expect.addr = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
test_free(expect.addr);
test_free(expect.addr); /* Double-free. */
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
static void test_invalid_addr_free(struct kunit *test)
{
const size_t size = 32;
struct expect_report expect = {
.type = KFENCE_ERROR_INVALID_FREE,
.fn = test_invalid_addr_free,
};
char *buf;
setup_test_cache(test, size, 0, NULL);
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
expect.addr = buf + 1; /* Free on invalid address. */
test_free(expect.addr); /* Invalid address free. */
test_free(buf); /* No error. */
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
static void test_corruption(struct kunit *test)
{
size_t size = 32;
struct expect_report expect = {
.type = KFENCE_ERROR_CORRUPTION,
.fn = test_corruption,
};
char *buf;
setup_test_cache(test, size, 0, NULL);
/* Test both sides. */
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_LEFT);
expect.addr = buf + size;
WRITE_ONCE(*expect.addr, 42);
test_free(buf);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_RIGHT);
expect.addr = buf - 1;
WRITE_ONCE(*expect.addr, 42);
test_free(buf);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* KFENCE is unable to detect an OOB if the allocation's alignment requirements
* leave a gap between the object and the guard page. Specifically, an
* allocation of e.g. 73 bytes is aligned on 8 and 128 bytes for SLUB or SLAB
* respectively. Therefore it is impossible for the allocated object to
* contiguously line up with the right guard page.
*
* However, we test that an access to memory beyond the gap results in KFENCE
* detecting an OOB access.
*/
static void test_kmalloc_aligned_oob_read(struct kunit *test)
{
const size_t size = 73;
const size_t align = kmalloc_cache_alignment(size);
struct expect_report expect = {
.type = KFENCE_ERROR_OOB,
.fn = test_kmalloc_aligned_oob_read,
.is_write = false,
};
char *buf;
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_RIGHT);
/*
* The object is offset to the right, so there won't be an OOB to the
* left of it.
*/
READ_ONCE(*(buf - 1));
KUNIT_EXPECT_FALSE(test, report_available());
/*
* @buf must be aligned on @align, therefore buf + size belongs to the
* same page -> no OOB.
*/
READ_ONCE(*(buf + size));
KUNIT_EXPECT_FALSE(test, report_available());
/* Overflowing by @align bytes will result in an OOB. */
expect.addr = buf + size + align;
READ_ONCE(*expect.addr);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
test_free(buf);
}
static void test_kmalloc_aligned_oob_write(struct kunit *test)
{
const size_t size = 73;
struct expect_report expect = {
.type = KFENCE_ERROR_CORRUPTION,
.fn = test_kmalloc_aligned_oob_write,
};
char *buf;
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_RIGHT);
/*
* The object is offset to the right, so we won't get a page
* fault immediately after it.
*/
expect.addr = buf + size;
WRITE_ONCE(*expect.addr, READ_ONCE(*expect.addr) + 1);
KUNIT_EXPECT_FALSE(test, report_available());
test_free(buf);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Test cache shrinking and destroying with KFENCE. */
static void test_shrink_memcache(struct kunit *test)
{
const size_t size = 32;
void *buf;
setup_test_cache(test, size, 0, NULL);
KUNIT_EXPECT_TRUE(test, test_cache);
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
kmem_cache_shrink(test_cache);
test_free(buf);
KUNIT_EXPECT_FALSE(test, report_available());
}
static void ctor_set_x(void *obj)
{
/* Every object has at least 8 bytes. */
memset(obj, 'x', 8);
}
/* Ensure that SL*B does not modify KFENCE objects on bulk free. */
static void test_free_bulk(struct kunit *test)
{
int iter;
for (iter = 0; iter < 5; iter++) {
const size_t size = setup_test_cache(test, get_random_u32_inclusive(8, 307),
0, (iter & 1) ? ctor_set_x : NULL);
void *objects[] = {
test_alloc(test, size, GFP_KERNEL, ALLOCATE_RIGHT),
test_alloc(test, size, GFP_KERNEL, ALLOCATE_NONE),
test_alloc(test, size, GFP_KERNEL, ALLOCATE_LEFT),
test_alloc(test, size, GFP_KERNEL, ALLOCATE_NONE),
test_alloc(test, size, GFP_KERNEL, ALLOCATE_NONE),
};
kmem_cache_free_bulk(test_cache, ARRAY_SIZE(objects), objects);
KUNIT_ASSERT_FALSE(test, report_available());
test_cache_destroy();
}
}
/* Test init-on-free works. */
static void test_init_on_free(struct kunit *test)
{
const size_t size = 32;
struct expect_report expect = {
.type = KFENCE_ERROR_UAF,
.fn = test_init_on_free,
.is_write = false,
};
int i;
KFENCE_TEST_REQUIRES(test, IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON));
/* Assume it hasn't been disabled on command line. */
setup_test_cache(test, size, 0, NULL);
expect.addr = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
for (i = 0; i < size; i++)
expect.addr[i] = i + 1;
test_free(expect.addr);
for (i = 0; i < size; i++) {
/*
* This may fail if the page was recycled by KFENCE and then
* written to again -- this however, is near impossible with a
* default config.
*/
KUNIT_EXPECT_EQ(test, expect.addr[i], (char)0);
if (!i) /* Only check first access to not fail test if page is ever re-protected. */
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
}
/* Ensure that constructors work properly. */
static void test_memcache_ctor(struct kunit *test)
{
const size_t size = 32;
char *buf;
int i;
setup_test_cache(test, size, 0, ctor_set_x);
buf = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
for (i = 0; i < 8; i++)
KUNIT_EXPECT_EQ(test, buf[i], (char)'x');
test_free(buf);
KUNIT_EXPECT_FALSE(test, report_available());
}
/* Test that memory is zeroed if requested. */
static void test_gfpzero(struct kunit *test)
{
const size_t size = PAGE_SIZE; /* PAGE_SIZE so we can use ALLOCATE_ANY. */
char *buf1, *buf2;
int i;
/* Skip if we think it'd take too long. */
KFENCE_TEST_REQUIRES(test, kfence_sample_interval <= 100);
setup_test_cache(test, size, 0, NULL);
buf1 = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
for (i = 0; i < size; i++)
buf1[i] = i + 1;
test_free(buf1);
/* Try to get same address again -- this can take a while. */
for (i = 0;; i++) {
buf2 = test_alloc(test, size, GFP_KERNEL | __GFP_ZERO, ALLOCATE_ANY);
if (buf1 == buf2)
break;
test_free(buf2);
if (kthread_should_stop() || (i == CONFIG_KFENCE_NUM_OBJECTS)) {
kunit_warn(test, "giving up ... cannot get same object back\n");
return;
}
cond_resched();
}
for (i = 0; i < size; i++)
KUNIT_EXPECT_EQ(test, buf2[i], (char)0);
test_free(buf2);
KUNIT_EXPECT_FALSE(test, report_available());
}
static void test_invalid_access(struct kunit *test)
{
const struct expect_report expect = {
.type = KFENCE_ERROR_INVALID,
.fn = test_invalid_access,
.addr = &__kfence_pool[10],
.is_write = false,
};
READ_ONCE(__kfence_pool[10]);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Test SLAB_TYPESAFE_BY_RCU works. */
static void test_memcache_typesafe_by_rcu(struct kunit *test)
{
const size_t size = 32;
struct expect_report expect = {
.type = KFENCE_ERROR_UAF,
.fn = test_memcache_typesafe_by_rcu,
.is_write = false,
};
setup_test_cache(test, size, SLAB_TYPESAFE_BY_RCU, NULL);
KUNIT_EXPECT_TRUE(test, test_cache); /* Want memcache. */
expect.addr = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY);
*expect.addr = 42;
rcu_read_lock();
test_free(expect.addr);
KUNIT_EXPECT_EQ(test, *expect.addr, (char)42);
/*
* Up to this point, memory should not have been freed yet, and
* therefore there should be no KFENCE report from the above access.
*/
rcu_read_unlock();
/* Above access to @expect.addr should not have generated a report! */
KUNIT_EXPECT_FALSE(test, report_available());
/* Only after rcu_barrier() is the memory guaranteed to be freed. */
rcu_barrier();
/* Expect use-after-free. */
KUNIT_EXPECT_EQ(test, *expect.addr, (char)42);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Test krealloc(). */
static void test_krealloc(struct kunit *test)
{
const size_t size = 32;
const struct expect_report expect = {
.type = KFENCE_ERROR_UAF,
.fn = test_krealloc,
.addr = test_alloc(test, size, GFP_KERNEL, ALLOCATE_ANY),
.is_write = false,
};
char *buf = expect.addr;
int i;
KUNIT_EXPECT_FALSE(test, test_cache);
KUNIT_EXPECT_EQ(test, ksize(buf), size); /* Precise size match after KFENCE alloc. */
for (i = 0; i < size; i++)
buf[i] = i + 1;
/* Check that we successfully change the size. */
buf = krealloc(buf, size * 3, GFP_KERNEL); /* Grow. */
/* Note: Might no longer be a KFENCE alloc. */
KUNIT_EXPECT_GE(test, ksize(buf), size * 3);
for (i = 0; i < size; i++)
KUNIT_EXPECT_EQ(test, buf[i], (char)(i + 1));
for (; i < size * 3; i++) /* Fill to extra bytes. */
buf[i] = i + 1;
buf = krealloc(buf, size * 2, GFP_KERNEL); /* Shrink. */
KUNIT_EXPECT_GE(test, ksize(buf), size * 2);
for (i = 0; i < size * 2; i++)
KUNIT_EXPECT_EQ(test, buf[i], (char)(i + 1));
buf = krealloc(buf, 0, GFP_KERNEL); /* Free. */
KUNIT_EXPECT_EQ(test, (unsigned long)buf, (unsigned long)ZERO_SIZE_PTR);
KUNIT_ASSERT_FALSE(test, report_available()); /* No reports yet! */
READ_ONCE(*expect.addr); /* Ensure krealloc() actually freed earlier KFENCE object. */
KUNIT_ASSERT_TRUE(test, report_matches(&expect));
}
/* Test that some objects from a bulk allocation belong to KFENCE pool. */
static void test_memcache_alloc_bulk(struct kunit *test)
{
const size_t size = 32;
bool pass = false;
unsigned long timeout;
setup_test_cache(test, size, 0, NULL);
KUNIT_EXPECT_TRUE(test, test_cache); /* Want memcache. */
/*
* 100x the sample interval should be more than enough to ensure we get
* a KFENCE allocation eventually.
*/
timeout = jiffies + msecs_to_jiffies(100 * kfence_sample_interval);
do {
void *objects[100];
int i, num = kmem_cache_alloc_bulk(test_cache, GFP_ATOMIC, ARRAY_SIZE(objects),
objects);
if (!num)
continue;
for (i = 0; i < ARRAY_SIZE(objects); i++) {
if (is_kfence_address(objects[i])) {
pass = true;
break;
}
}
kmem_cache_free_bulk(test_cache, num, objects);
/*
* kmem_cache_alloc_bulk() disables interrupts, and calling it
* in a tight loop may not give KFENCE a chance to switch the
* static branch. Call cond_resched() to let KFENCE chime in.
*/
cond_resched();
} while (!pass && time_before(jiffies, timeout));
KUNIT_EXPECT_TRUE(test, pass);
KUNIT_EXPECT_FALSE(test, report_available());
}
/*
* KUnit does not provide a way to provide arguments to tests, and we encode
* additional info in the name. Set up 2 tests per test case, one using the
* default allocator, and another using a custom memcache (suffix '-memcache').
*/
#define KFENCE_KUNIT_CASE(test_name) \
{ .run_case = test_name, .name = #test_name }, \
{ .run_case = test_name, .name = #test_name "-memcache" }
static struct kunit_case kfence_test_cases[] = {
KFENCE_KUNIT_CASE(test_out_of_bounds_read),
KFENCE_KUNIT_CASE(test_out_of_bounds_write),
KFENCE_KUNIT_CASE(test_use_after_free_read),
KFENCE_KUNIT_CASE(test_double_free),
KFENCE_KUNIT_CASE(test_invalid_addr_free),
KFENCE_KUNIT_CASE(test_corruption),
KFENCE_KUNIT_CASE(test_free_bulk),
KFENCE_KUNIT_CASE(test_init_on_free),
KUNIT_CASE(test_kmalloc_aligned_oob_read),
KUNIT_CASE(test_kmalloc_aligned_oob_write),
KUNIT_CASE(test_shrink_memcache),
KUNIT_CASE(test_memcache_ctor),
KUNIT_CASE(test_invalid_access),
KUNIT_CASE(test_gfpzero),
KUNIT_CASE(test_memcache_typesafe_by_rcu),
KUNIT_CASE(test_krealloc),
KUNIT_CASE(test_memcache_alloc_bulk),
{},
};
/* ===== End test cases ===== */
static int test_init(struct kunit *test)
{
unsigned long flags;
int i;
if (!__kfence_pool)
return -EINVAL;
spin_lock_irqsave(&observed.lock, flags);
for (i = 0; i < ARRAY_SIZE(observed.lines); i++)
observed.lines[i][0] = '\0';
observed.nlines = 0;
spin_unlock_irqrestore(&observed.lock, flags);
/* Any test with 'memcache' in its name will want a memcache. */
if (strstr(test->name, "memcache"))
test->priv = TEST_PRIV_WANT_MEMCACHE;
else
test->priv = NULL;
return 0;
}
static void test_exit(struct kunit *test)
{
test_cache_destroy();
}
static int kfence_suite_init(struct kunit_suite *suite)
{
register_trace_console(probe_console, NULL);
return 0;
}
static void kfence_suite_exit(struct kunit_suite *suite)
{
unregister_trace_console(probe_console, NULL);
tracepoint_synchronize_unregister();
}
static struct kunit_suite kfence_test_suite = {
.name = "kfence",
.test_cases = kfence_test_cases,
.init = test_init,
.exit = test_exit,
.suite_init = kfence_suite_init,
.suite_exit = kfence_suite_exit,
};
kunit_test_suites(&kfence_test_suite);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Alexander Potapenko <glider@google.com>, Marco Elver <elver@google.com>");