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kmsan: introduce test_memcpy_initialized_gap()

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Add a regression test for the special case where memcpy() previously
failed to correctly set the origins: if upon memcpy() four aligned
initialized bytes with a zero origin value ended up split between two
aligned four-byte chunks, one of those chunks could've received the zero
origin value even despite it contained uninitialized bytes from other
writes.

Link: https://lkml.kernel.org/r/20230911145702.2663753-4-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Marco Elver <elver@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alexander Potapenko 2023-09-11 16:57:02 +02:00 committed by Andrew Morton
parent c3ab4873c8
commit 46fa84a2b9
1 changed files with 53 additions and 0 deletions
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53
mm/kmsan/kmsan_test.c
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@ -486,6 +486,58 @@ static void test_memcpy_aligned_to_unaligned(struct kunit *test)
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) \
@ -579,6 +631,7 @@ static struct kunit_case kmsan_test_cases[] = {
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),