kasan: test: clean up ksize_uaf

Some KASAN tests use global variables to store function returns values so
that the compiler doesn't optimize away these functions.

ksize_uaf() doesn't call any functions, so it doesn't need to use
kasan_int_result.  Use volatile accesses instead, to be consistent with
other similar tests.

Link: https://lkml.kernel.org/r/a1fc34faca4650f4a6e4dfb3f8d8d82c82eb953a.1628779805.git.andreyknvl@gmail.comSigned-off-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/test_kasan.c

@@ -737,8 +737,8 @@ static void ksize_uaf(struct kunit *test)
 	kfree(ptr);
 
 	KUNIT_EXPECT_KASAN_FAIL(test, ksize(ptr));
-	KUNIT_EXPECT_KASAN_FAIL(test, kasan_int_result = *ptr);
-	KUNIT_EXPECT_KASAN_FAIL(test, kasan_int_result = *(ptr + size));
+	KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[0]);
+	KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
 }
 
 static void kasan_stack_oob(struct kunit *test)