The patch titled
Subject: kmsan: another take at fixing memcpy tests
has been added to the -mm mm-unstable branch. Its filename is
kmsan-another-take-at-fixing-memcpy-tests.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kmsan-another-take-at-fixing-memcpy-tests.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: kmsan: another take at fixing memcpy tests
Date: Fri, 3 Mar 2023 15:14:31 +0100
commit 5478afc55a21 ("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@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Helge Deller <deller@xxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/kmsan/kmsan_test.c~kmsan-another-take-at-fixing-memcpy-tests
+++ a/mm/kmsan/kmsan_test.c
@@ -408,6 +408,37 @@ static void test_printk(struct kunit *te
}
/*
+ * 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_align
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_unali
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_unali
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 *arra
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_case
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),
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
x86-kmsan-dont-rename-memintrinsics-in-uninstrumented-files.patch
kmsan-another-take-at-fixing-memcpy-tests.patch
x86-kmsan-use-c-versions-of-memset16-memset32-memset64.patch
kmsan-add-memsetxx-tests.patch
