path: root/mm/kmsan/kmsan_test.c

// 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