kmsan: introduce test_unpoison_memory()

Add a regression test to ensure that kmsan_unpoison_memory() works the
same as an unpoisoning operation added by the instrumentation.

The test has two subtests: one that checks the instrumentation, and one
that checks kmsan_unpoison_memory().  Each subtest initializes the first
byte of a 4-byte buffer, then checks that the other 3 bytes are
uninitialized.

[glider@google.com: change description, remove comment about failing test case]
Link: https://lkml.kernel.org/r/20240528104807.738758-2-glider@google.com
Signed-off-by: Brian Johannesmeyer <bjohannesmeyer@gmail.com>
Link: https://lore.kernel.org/lkml/20240524232804.1984355-1-bjohannesmeyer@gmail.com/T/
Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/kmsan/kmsan_test.c b/mm/kmsan/kmsan_test.c
index 07d3a3a5a9c520b4596a4fdc454e2d8e6c748809..018069aba92bec3fd1156461444a66ab90b5a1ff 100644 (file)
--- a/mm/kmsan/kmsan_test.c
+++ b/mm/kmsan/kmsan_test.c
@@ -614,6 +614,32 @@ static void test_stackdepot_roundtrip(struct kunit *test)
        KUNIT_EXPECT_TRUE(test, report_matches(&expect));
 }
 
+/*
+ * Test case: ensure that kmsan_unpoison_memory() and the instrumentation work
+ * the same.
+ */
+static void test_unpoison_memory(struct kunit *test)
+{
+       EXPECTATION_UNINIT_VALUE_FN(expect, "test_unpoison_memory");
+       volatile char a[4], b[4];
+
+       kunit_info(
+               test,
+               "unpoisoning via the instrumentation vs. kmsan_unpoison_memory() (2 UMR reports)\n");
+
+       /* Initialize a[0] and check a[1]--a[3]. */
+       a[0] = 0;
+       kmsan_check_memory((char *)&a[1], 3);
+       KUNIT_EXPECT_TRUE(test, report_matches(&expect));
+
+       report_reset();
+
+       /* Initialize b[0] and check b[1]--b[3]. */
+       kmsan_unpoison_memory((char *)&b[0], 1);
+       kmsan_check_memory((char *)&b[1], 3);
+       KUNIT_EXPECT_TRUE(test, report_matches(&expect));
+}
+
 static struct kunit_case kmsan_test_cases[] = {
        KUNIT_CASE(test_uninit_kmalloc),
        KUNIT_CASE(test_init_kmalloc),
@@ -637,6 +663,7 @@ static struct kunit_case kmsan_test_cases[] = {
        KUNIT_CASE(test_memset64),
        KUNIT_CASE(test_long_origin_chain),
        KUNIT_CASE(test_stackdepot_roundtrip),
+       KUNIT_CASE(test_unpoison_memory),
        {},
 };