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// SPDX-License-Identifier: GPL-2.0
/*
* Test cases for KMSAN.
* 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) 2021-2022, Google LLC.
* Author: Alexander Potapenko <glider@google.com>
*
*/
#include <kunit/test.h>
#include "kmsan.h"
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/kmsan.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 <linux/vmalloc.h>
#include <trace/events/printk.h>
static DEFINE_PER_CPU(int, per_cpu_var);
/* Report as observed from console. */
static struct {
spinlock_t lock;
bool available;
bool ignore; /* Stop console output collection. */
char header[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;
if (observed.ignore)
return;
spin_lock_irqsave(&observed.lock, flags);
if (strnstr(buf, "BUG: KMSAN: ", len)) {
/*
* KMSAN 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.header, buf,
min(len + 1, sizeof(observed.header)));
WRITE_ONCE(observed.available, true);
observed.ignore = true;
}
spin_unlock_irqrestore(&observed.lock, flags);
}
/* Check if a report related to the test exists. */
static bool report_available(void)
{
return READ_ONCE(observed.available);
}
/* Reset observed.available, so that the test can trigger another report. */
static void report_reset(void)
{
unsigned long flags;
spin_lock_irqsave(&observed.lock, flags);
WRITE_ONCE(observed.available, false);
observed.ignore = false;
spin_unlock_irqrestore(&observed.lock, flags);
}
/* Information we expect in a report. */
struct expect_report {
const char *error_type; /* Error type. */
/*
* Kernel symbol from the error header, or NULL if no report is
* expected.
*/
const char *symbol;
};
/* Check observed report matches information in @r. */
static bool report_matches(const struct expect_report *r)
{
typeof(observed.header) expected_header;
unsigned long flags;
bool ret = false;
const char *end;
char *cur;
/* Doubled-checked locking. */
if (!report_available() || !r->symbol)
return (!report_available() && !r->symbol);
/* Generate expected report contents. */
/* Title */
cur = expected_header;
end = &expected_header[sizeof(expected_header) - 1];
cur += scnprintf(cur, end - cur, "BUG: KMSAN: %s", r->error_type);
scnprintf(cur, end - cur, " in %s", r->symbol);
/* The exact offset won't match, remove it; also strip module name. */
cur = strchr(expected_header, '+');
if (cur)
*cur = '\0';
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.header, expected_header);
out:
spin_unlock_irqrestore(&observed.lock, flags);
return ret;
}
/* ===== Test cases ===== */
/* Prevent replacing branch with select in LLVM. */
static noinline void check_true(char *arg)
{
pr_info("%s is true\n", arg);
}
static noinline void check_false(char *arg)
{
pr_info("%s is false\n", arg);
}
#define USE(x) \
do { \
if (x) \
check_true(#x); \
else \
check_false(#x); \
} while (0)
#define EXPECTATION_ETYPE_FN(e, reason, fn) \
struct expect_report e = { \
.error_type = reason, \
.symbol = fn, \
}
#define EXPECTATION_NO_REPORT(e) EXPECTATION_ETYPE_FN(e, NULL, NULL)
#define EXPECTATION_UNINIT_VALUE_FN(e, fn) \
EXPECTATION_ETYPE_FN(e, "uninit-value", fn)
#define EXPECTATION_UNINIT_VALUE(e) EXPECTATION_UNINIT_VALUE_FN(e, __func__)
#define EXPECTATION_USE_AFTER_FREE(e) \
EXPECTATION_ETYPE_FN(e, "use-after-free", __func__)
/* Test case: ensure that kmalloc() returns uninitialized memory. */
static void test_uninit_kmalloc(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE(expect);
int *ptr;
kunit_info(test, "uninitialized kmalloc test (UMR report)\n");
ptr = kmalloc(sizeof(*ptr), GFP_KERNEL);
USE(*ptr);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that kmalloc'ed memory becomes initialized after memset().
*/
static void test_init_kmalloc(struct kunit *test)
{
EXPECTATION_NO_REPORT(expect);
int *ptr;
kunit_info(test, "initialized kmalloc test (no reports)\n");
ptr = kmalloc(sizeof(*ptr), GFP_KERNEL);
memset(ptr, 0, sizeof(*ptr));
USE(*ptr);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Test case: ensure that kzalloc() returns initialized memory. */
static void test_init_kzalloc(struct kunit *test)
{
EXPECTATION_NO_REPORT(expect);
int *ptr;
kunit_info(test, "initialized kzalloc test (no reports)\n");
ptr = kzalloc(sizeof(*ptr), GFP_KERNEL);
USE(*ptr);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Test case: ensure that local variables are uninitialized by default. */
static void test_uninit_stack_var(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE(expect);
volatile int cond;
kunit_info(test, "uninitialized stack variable (UMR report)\n");
USE(cond);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Test case: ensure that local variables with initializers are initialized. */
static void test_init_stack_var(struct kunit *test)
{
EXPECTATION_NO_REPORT(expect);
volatile int cond = 1;
kunit_info(test, "initialized stack variable (no reports)\n");
USE(cond);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
static noinline void two_param_fn_2(int arg1, int arg2)
{
USE(arg1);
USE(arg2);
}
static noinline void one_param_fn(int arg)
{
two_param_fn_2(arg, arg);
USE(arg);
}
static noinline void two_param_fn(int arg1, int arg2)
{
int init = 0;
one_param_fn(init);
USE(arg1);
USE(arg2);
}
static void test_params(struct kunit *test)
{
#ifdef CONFIG_KMSAN_CHECK_PARAM_RETVAL
/*
* With eager param/retval checking enabled, KMSAN will report an error
* before the call to two_param_fn().
*/
EXPECTATION_UNINIT_VALUE_FN(expect, "test_params");
#else
EXPECTATION_UNINIT_VALUE_FN(expect, "two_param_fn");
#endif
volatile int uninit, init = 1;
kunit_info(test,
"uninit passed through a function parameter (UMR report)\n");
two_param_fn(uninit, init);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
static int signed_sum3(int a, int b, int c)
{
return a + b + c;
}
/*
* Test case: ensure that uninitialized values are tracked through function
* arguments.
*/
static void test_uninit_multiple_params(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE(expect);
volatile char b = 3, c;
volatile int a;
kunit_info(test, "uninitialized local passed to fn (UMR report)\n");
USE(signed_sum3(a, b, c));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Helper function to make an array uninitialized. */
static noinline void do_uninit_local_array(char *array, int start, int stop)
{
volatile char uninit;
for (int i = start; i < stop; i++)
array[i] = uninit;
}
/*
* Test case: ensure kmsan_check_memory() reports an error when checking
* uninitialized memory.
*/
static void test_uninit_kmsan_check_memory(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE_FN(expect, "test_uninit_kmsan_check_memory");
volatile char local_array[8];
kunit_info(
test,
"kmsan_check_memory() called on uninit local (UMR report)\n");
do_uninit_local_array((char *)local_array, 5, 7);
kmsan_check_memory((char *)local_array, 8);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: check that a virtual memory range created with vmap() from
* initialized pages is still considered as initialized.
*/
static void test_init_kmsan_vmap_vunmap(struct kunit *test)
{
EXPECTATION_NO_REPORT(expect);
const int npages = 2;
struct page **pages;
void *vbuf;
kunit_info(test, "pages initialized via vmap (no reports)\n");
pages = kmalloc_array(npages, sizeof(*pages), GFP_KERNEL);
for (int i = 0; i < npages; i++)
pages[i] = alloc_page(GFP_KERNEL);
vbuf = vmap(pages, npages, VM_MAP, PAGE_KERNEL);
memset(vbuf, 0xfe, npages * PAGE_SIZE);
for (int i = 0; i < npages; i++)
kmsan_check_memory(page_address(pages[i]), PAGE_SIZE);
if (vbuf)
vunmap(vbuf);
for (int i = 0; i < npages; i++) {
if (pages[i])
__free_page(pages[i]);
}
kfree(pages);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that memset() can initialize a buffer allocated via
* vmalloc().
*/
static void test_init_vmalloc(struct kunit *test)
{
EXPECTATION_NO_REPORT(expect);
int npages = 8;
char *buf;
kunit_info(test, "vmalloc buffer can be initialized (no reports)\n");
buf = vmalloc(PAGE_SIZE * npages);
buf[0] = 1;
memset(buf, 0xfe, PAGE_SIZE * npages);
USE(buf[0]);
for (int i = 0; i < npages; i++)
kmsan_check_memory(&buf[PAGE_SIZE * i], PAGE_SIZE);
vfree(buf);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Test case: ensure that use-after-free reporting works. */
static void test_uaf(struct kunit *test)
{
EXPECTATION_USE_AFTER_FREE(expect);
volatile int value;
volatile int *var;
kunit_info(test, "use-after-free in kmalloc-ed buffer (UMR report)\n");
var = kmalloc(80, GFP_KERNEL);
var[3] = 0xfeedface;
kfree((int *)var);
/* Copy the invalid value before checking it. */
value = var[3];
USE(value);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that uninitialized values are propagated through per-CPU
* memory.
*/
static void test_percpu_propagate(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE(expect);
volatile int uninit, check;
kunit_info(test,
"uninit local stored to per_cpu memory (UMR report)\n");
this_cpu_write(per_cpu_var, uninit);
check = this_cpu_read(per_cpu_var);
USE(check);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that passing uninitialized values to printk() leads to an
* error report.
*/
static void test_printk(struct kunit *test)
{
#ifdef CONFIG_KMSAN_CHECK_PARAM_RETVAL
/*
* With eager param/retval checking enabled, KMSAN will report an error
* before the call to pr_info().
*/
EXPECTATION_UNINIT_VALUE_FN(expect, "test_printk");
#else
EXPECTATION_UNINIT_VALUE_FN(expect, "number");
#endif
volatile int uninit;
kunit_info(test, "uninit local passed to pr_info() (UMR report)\n");
pr_info("%px contains %d\n", &uninit, uninit);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Prevent the compiler from inlining a memcpy() call. */
static noinline void *memcpy_noinline(volatile void *dst,
const volatile void *src, size_t size)
{
return memcpy((void *)dst, (const void *)src, size);
}
/* Test case: ensure that memcpy() correctly copies initialized values. */
static void test_init_memcpy(struct kunit *test)
{
EXPECTATION_NO_REPORT(expect);
volatile long long src;
volatile long long dst = 0;
src = 1;
kunit_info(
test,
"memcpy()ing aligned initialized src to aligned dst (no reports)\n");
memcpy_noinline((void *)&dst, (void *)&src, sizeof(src));
kmsan_check_memory((void *)&dst, sizeof(dst));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that memcpy() correctly copies uninitialized values between
* aligned `src` and `dst`.
*/
static void test_memcpy_aligned_to_aligned(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE_FN(expect, "test_memcpy_aligned_to_aligned");
volatile int uninit_src;
volatile int dst = 0;
kunit_info(
test,
"memcpy()ing aligned uninit src to aligned dst (UMR report)\n");
memcpy_noinline((void *)&dst, (void *)&uninit_src, sizeof(uninit_src));
kmsan_check_memory((void *)&dst, sizeof(dst));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that memcpy() correctly copies uninitialized values between
* aligned `src` and unaligned `dst`.
*
* Copying aligned 4-byte value to an unaligned one leads to touching two
* aligned 4-byte values. This test case checks that KMSAN correctly reports an
* error on the mentioned two values.
*/
static void test_memcpy_aligned_to_unaligned(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE_FN(expect, "test_memcpy_aligned_to_unaligned");
volatile int uninit_src;
volatile char dst[8] = { 0 };
kunit_info(
test,
"memcpy()ing aligned uninit src to unaligned dst (UMR report)\n");
kmsan_check_memory((void *)&uninit_src, sizeof(uninit_src));
memcpy_noinline((void *)&dst[1], (void *)&uninit_src,
sizeof(uninit_src));
kmsan_check_memory((void *)dst, 4);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
report_reset();
kmsan_check_memory((void *)&dst[4], sizeof(uninit_src));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that origin slots do not accidentally get overwritten with
* zeroes during memcpy().
*
* Previously, when copying memory from an aligned buffer to an unaligned one,
* if there were zero origins corresponding to zero shadow values in the source
* buffer, they could have ended up being copied to nonzero shadow values in the
* destination buffer:
*
* memcpy(0xffff888080a00000, 0xffff888080900002, 8)
*
* src (0xffff888080900002): ..xx .... xx..
* src origins: o111 0000 o222
* dst (0xffff888080a00000): xx.. ..xx
* dst origins: o111 0000
* (or 0000 o222)
*
* (here . stands for an initialized byte, and x for an uninitialized one.
*
* Ensure that this does not happen anymore, and for both destination bytes
* the origin is nonzero (i.e. KMSAN reports an error).
*/
static void test_memcpy_initialized_gap(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE_FN(expect, "test_memcpy_initialized_gap");
volatile char uninit_src[12];
volatile char dst[8] = { 0 };
kunit_info(
test,
"unaligned 4-byte initialized value gets a nonzero origin after memcpy() - (2 UMR reports)\n");
uninit_src[0] = 42;
uninit_src[1] = 42;
uninit_src[4] = 42;
uninit_src[5] = 42;
uninit_src[6] = 42;
uninit_src[7] = 42;
uninit_src[10] = 42;
uninit_src[11] = 42;
memcpy_noinline((void *)&dst[0], (void *)&uninit_src[2], 8);
kmsan_check_memory((void *)&dst[0], 4);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
report_reset();
kmsan_check_memory((void *)&dst[2], 4);
KUNIT_EXPECT_FALSE(test, report_matches(&expect));
report_reset();
kmsan_check_memory((void *)&dst[4], 4);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/* Generate test cases for memset16(), memset32(), memset64(). */
#define DEFINE_TEST_MEMSETXX(size) \
static void test_memset##size(struct kunit *test) \
{ \
EXPECTATION_NO_REPORT(expect); \
volatile uint##size##_t uninit; \
\
kunit_info(test, \
"memset" #size "() should initialize memory\n"); \
memset##size((uint##size##_t *)&uninit, 0, 1); \
kmsan_check_memory((void *)&uninit, sizeof(uninit)); \
KUNIT_EXPECT_TRUE(test, report_matches(&expect)); \
}
DEFINE_TEST_MEMSETXX(16)
DEFINE_TEST_MEMSETXX(32)
DEFINE_TEST_MEMSETXX(64)
static noinline void fibonacci(int *array, int size, int start)
{
if (start < 2 || (start == size))
return;
array[start] = array[start - 1] + array[start - 2];
fibonacci(array, size, start + 1);
}
static void test_long_origin_chain(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE_FN(expect, "test_long_origin_chain");
/* (KMSAN_MAX_ORIGIN_DEPTH * 2) recursive calls to fibonacci(). */
volatile int accum[KMSAN_MAX_ORIGIN_DEPTH * 2 + 2];
int last = ARRAY_SIZE(accum) - 1;
kunit_info(
test,
"origin chain exceeding KMSAN_MAX_ORIGIN_DEPTH (UMR report)\n");
/*
* We do not set accum[1] to 0, so the uninitializedness will be carried
* over to accum[2..last].
*/
accum[0] = 1;
fibonacci((int *)accum, ARRAY_SIZE(accum), 2);
kmsan_check_memory((void *)&accum[last], sizeof(int));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that saving/restoring/printing stacks to/from stackdepot
* does not trigger errors.
*
* KMSAN uses stackdepot to store origin stack traces, that's why we do not
* instrument lib/stackdepot.c. Yet it must properly mark its outputs as
* initialized because other kernel features (e.g. netdev tracker) may also
* access stackdepot from instrumented code.
*/
static void test_stackdepot_roundtrip(struct kunit *test)
{
unsigned long src_entries[16], *dst_entries;
unsigned int src_nentries, dst_nentries;
EXPECTATION_NO_REPORT(expect);
depot_stack_handle_t handle;
kunit_info(test, "testing stackdepot roundtrip (no reports)\n");
src_nentries =
stack_trace_save(src_entries, ARRAY_SIZE(src_entries), 1);
handle = stack_depot_save(src_entries, src_nentries, GFP_KERNEL);
stack_depot_print(handle);
dst_nentries = stack_depot_fetch(handle, &dst_entries);
KUNIT_EXPECT_TRUE(test, src_nentries == dst_nentries);
kmsan_check_memory((void *)dst_entries,
sizeof(*dst_entries) * dst_nentries);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Test case: ensure that kmsan_unpoison_memory() and the instrumentation work
* the same.
*/
static void test_unpoison_memory(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE_FN(expect, "test_unpoison_memory");
volatile char a[4], b[4];
kunit_info(
test,
"unpoisoning via the instrumentation vs. kmsan_unpoison_memory() (2 UMR reports)\n");
/* Initialize a[0] and check a[1]--a[3]. */
a[0] = 0;
kmsan_check_memory((char *)&a[1], 3);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
report_reset();
/* Initialize b[0] and check b[1]--b[3]. */
kmsan_unpoison_memory((char *)&b[0], 1);
kmsan_check_memory((char *)&b[1], 3);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
static struct kunit_case kmsan_test_cases[] = {
KUNIT_CASE(test_uninit_kmalloc),
KUNIT_CASE(test_init_kmalloc),
KUNIT_CASE(test_init_kzalloc),
KUNIT_CASE(test_uninit_stack_var),
KUNIT_CASE(test_init_stack_var),
KUNIT_CASE(test_params),
KUNIT_CASE(test_uninit_multiple_params),
KUNIT_CASE(test_uninit_kmsan_check_memory),
KUNIT_CASE(test_init_kmsan_vmap_vunmap),
KUNIT_CASE(test_init_vmalloc),
KUNIT_CASE(test_uaf),
KUNIT_CASE(test_percpu_propagate),
KUNIT_CASE(test_printk),
KUNIT_CASE(test_init_memcpy),
KUNIT_CASE(test_memcpy_aligned_to_aligned),
KUNIT_CASE(test_memcpy_aligned_to_unaligned),
KUNIT_CASE(test_memcpy_initialized_gap),
KUNIT_CASE(test_memset16),
KUNIT_CASE(test_memset32),
KUNIT_CASE(test_memset64),
KUNIT_CASE(test_long_origin_chain),
KUNIT_CASE(test_stackdepot_roundtrip),
KUNIT_CASE(test_unpoison_memory),
{},
};
/* ===== End test cases ===== */
static int test_init(struct kunit *test)
{
unsigned long flags;
spin_lock_irqsave(&observed.lock, flags);
observed.header[0] = '\0';
observed.ignore = false;
observed.available = false;
spin_unlock_irqrestore(&observed.lock, flags);
return 0;
}
static void test_exit(struct kunit *test)
{
}
static int orig_panic_on_kmsan;
static int kmsan_suite_init(struct kunit_suite *suite)
{
register_trace_console(probe_console, NULL);
orig_panic_on_kmsan = panic_on_kmsan;
panic_on_kmsan = 0;
return 0;
}
static void kmsan_suite_exit(struct kunit_suite *suite)
{
unregister_trace_console(probe_console, NULL);
tracepoint_synchronize_unregister();
panic_on_kmsan = orig_panic_on_kmsan;
}
static struct kunit_suite kmsan_test_suite = {
.name = "kmsan",
.test_cases = kmsan_test_cases,
.init = test_init,
.exit = test_exit,
.suite_init = kmsan_suite_init,
.suite_exit = kmsan_suite_exit,
};
kunit_test_suites(&kmsan_test_suite);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alexander Potapenko <glider@google.com>");