Commit 3ff16d30 authored by David Gow's avatar David Gow Committed by Linus Torvalds
Browse files

kasan: test: improve failure message in KUNIT_EXPECT_KASAN_FAIL() 

The KUNIT_EXPECT_KASAN_FAIL() macro currently uses KUNIT_EXPECT_EQ() to
compare fail_data.report_expected and fail_data.report_found.  This always
gave a somewhat useless error message on failure, but the addition of
extra compile-time checking with READ_ONCE() has caused it to get much
longer, and be truncated before anything useful is displayed.

Instead, just check fail_data.report_found by hand (we've just set
report_expected to 'true'), and print a better failure message with
KUNIT_FAIL().  Because of this, report_expected is no longer used
anywhere, and can be removed.

Beforehand, a failure in:
KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)area)[3100]);
would have looked like:
[22:00:34] [FAILED] vmalloc_oob
[22:00:34]     # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:991
[22:00:34]     Expected ({ do { extern void __compiletime_assert_705(void) __attribute__((__error__("Unsupported access size for {READ,WRITE}_ONCE()."))); if (!((sizeof(fail_data.report_expected) == sizeof(char) || sizeof(fail_data.repp
[22:00:34]     not ok 45 - vmalloc_oob

With this change, it instead looks like:
[22:04:04] [FAILED] vmalloc_oob
[22:04:04]     # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:993
[22:04:04]     KASAN failure expected in "((volatile char *)area)[3100]", but none occurred
[22:04:04]     not ok 45 - vmalloc_oob

Also update the example failure in the documentation to reflect this.

Link: https://lkml.kernel.org/r/20210606005531.165954-1-davidgow@google.com


Signed-off-by: default avatarDavid Gow <davidgow@google.com>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Acked-by: default avatarBrendan Higgins <brendanhiggins@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Daniel Axtens <dja@axtens.net>
Cc: David Gow <davidgow@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 336abff6

Documentation/dev-tools/kasan.rst

+4 −5
Original line number Diff line number Diff line
@@ -447,11 +447,10 @@ When a test fails due to a failed ``kmalloc``:: 


When a test fails due to a missing KASAN report::



        # kmalloc_double_kzfree: EXPECTATION FAILED at lib/test_kasan.c:629

        Expected kasan_data->report_expected == kasan_data->report_found, but

        kasan_data->report_expected == 1

        kasan_data->report_found == 0

        not ok 28 - kmalloc_double_kzfree

        # kmalloc_double_kzfree: EXPECTATION FAILED at lib/test_kasan.c:974

        KASAN failure expected in "kfree_sensitive(ptr)", but none occurred

        not ok 44 - kmalloc_double_kzfree





At the end the cumulative status of all KASAN tests is printed. On success::

include/linux/kasan.h

+0 −1
Original line number Diff line number Diff line
@@ -17,7 +17,6 @@ struct task_struct; 


/* kasan_data struct is used in KUnit tests for KASAN expected failures */

struct kunit_kasan_expectation {

	bool report_expected;

	bool report_found;

};

lib/test_kasan.c

+5 −6
Original line number Diff line number Diff line
@@ -55,7 +55,6 @@ static int kasan_test_init(struct kunit *test) 
	multishot = kasan_save_enable_multi_shot();

	kasan_set_tagging_report_once(false);

	fail_data.report_found = false;

	fail_data.report_expected = false;

	kunit_add_named_resource(test, NULL, NULL, &resource,

					"kasan_data", &fail_data);

	return 0;
@@ -94,20 +93,20 @@ static void kasan_test_exit(struct kunit *test) 
	    !kasan_async_mode_enabled())				\

		migrate_disable();					\

	KUNIT_EXPECT_FALSE(test, READ_ONCE(fail_data.report_found));	\

	WRITE_ONCE(fail_data.report_expected, true);			\

	barrier();							\

	expression;							\

	barrier();							\

	KUNIT_EXPECT_EQ(test,						\

			READ_ONCE(fail_data.report_expected),		\

			READ_ONCE(fail_data.report_found));		\

	if (!READ_ONCE(fail_data.report_found)) {			\

		KUNIT_FAIL(test, KUNIT_SUBTEST_INDENT "KASAN failure "	\

				"expected in \"" #expression		\

				 "\", but none occurred");		\

	}								\

	if (IS_ENABLED(CONFIG_KASAN_HW_TAGS)) {				\

		if (READ_ONCE(fail_data.report_found))			\

			kasan_enable_tagging_sync();			\

		migrate_enable();					\

	}								\

	WRITE_ONCE(fail_data.report_found, false);			\

	WRITE_ONCE(fail_data.report_expected, false);			\

} while (0)



#define KASAN_TEST_NEEDS_CONFIG_ON(test, config) do {			\