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kmsan: another take at fixing memcpy tests 

commit 5478afc55a ("kmsan: fix memcpy tests") uses OPTIMIZER_HIDE_VAR()
to hide the uninitialized var from the compiler optimizations.

However OPTIMIZER_HIDE_VAR(uninit) enforces an immediate check of @uninit,
so memcpy tests did not actually check the behavior of memcpy(), because
they always contained a KMSAN report.

Replace OPTIMIZER_HIDE_VAR() with a file-local macro that just clobbers
the memory with a barrier(), and add a test case for memcpy() that does
not expect an error report.

Also reflow kmsan_test.c with clang-format.

Link: https://lkml.kernel.org/r/20230303141433.3422671-2-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alexander Potapenko 2023-03-03 15:14:31 +01:00 committed by Andrew Morton
parent 6dc4bd4e2f
commit d340292553
1 changed files with 38 additions and 6 deletions
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44
mm/kmsan/kmsan_test.c
View File

@ -407,6 +407,37 @@ static void test_printk(struct kunit *test)
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
/*
* Prevent the compiler from optimizing @var away. Without this, Clang may
* notice that @var is uninitialized and drop memcpy() calls that use it.
*
* There is OPTIMIZER_HIDE_VAR() in linux/compier.h that we cannot use here,
* because it is implemented as inline assembly receiving @var as a parameter
* and will enforce a KMSAN check. Same is true for e.g. barrier_data(var).
*/
#define DO_NOT_OPTIMIZE(var) barrier()
/*
* Test case: ensure that memcpy() correctly copies initialized values.
* Also serves as a regression test to ensure DO_NOT_OPTIMIZE() does not cause
* extra checks.
*/
static void test_init_memcpy(struct kunit *test)
{
EXPECTATION_NO_REPORT(expect);
volatile int src;
volatile int dst = 0;
DO_NOT_OPTIMIZE(src);
src = 1;
kunit_info(
test,
"memcpy()ing aligned initialized src to aligned dst (no reports)\n");
memcpy((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`.
@ -420,7 +451,7 @@ static void test_memcpy_aligned_to_aligned(struct kunit *test)
kunit_info(
test,
"memcpy()ing aligned uninit src to aligned dst (UMR report)\n");
OPTIMIZER_HIDE_VAR(uninit_src);
DO_NOT_OPTIMIZE(uninit_src);
memcpy((void *)&dst, (void *)&uninit_src, sizeof(uninit_src));
kmsan_check_memory((void *)&dst, sizeof(dst));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
@ -443,7 +474,7 @@ static void test_memcpy_aligned_to_unaligned(struct kunit *test)
kunit_info(
test,
"memcpy()ing aligned uninit src to unaligned dst (UMR report)\n");
OPTIMIZER_HIDE_VAR(uninit_src);
DO_NOT_OPTIMIZE(uninit_src);
memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src));
kmsan_check_memory((void *)dst, 4);
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
@ -467,13 +498,14 @@ static void test_memcpy_aligned_to_unaligned2(struct kunit *test)
kunit_info(
test,
"memcpy()ing aligned uninit src to unaligned dst - part 2 (UMR report)\n");
OPTIMIZER_HIDE_VAR(uninit_src);
DO_NOT_OPTIMIZE(uninit_src);
memcpy((void *)&dst[1], (void *)&uninit_src, sizeof(uninit_src));
kmsan_check_memory((void *)&dst[4], sizeof(uninit_src));
KUNIT_EXPECT_TRUE(test, report_matches(&expect));
}
static noinline void fibonacci(int *array, int size, int start) {
static noinline void fibonacci(int *array, int size, int start)
{
if (start < 2 || (start == size))
return;
array[start] = array[start - 1] + array[start - 2];
@ -482,8 +514,7 @@ static noinline void fibonacci(int *array, int size, int start) {
static void test_long_origin_chain(struct kunit *test)
{
EXPECTATION_UNINIT_VALUE_FN(expect,
"test_long_origin_chain");
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;
@ -515,6 +546,7 @@ static struct kunit_case kmsan_test_cases[] = {
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_aligned_to_unaligned2),