kmsan: core: kmsan_in_runtime() should return true in NMI context

Without that, every call to __msan_poison_alloca() in NMI may end up
allocating memory, which is NMI-unsafe.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Alexander Potapenko <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: ramosian-glider

mm/kmsan/kmsan.h

@@ -124,6 +124,8 @@ static __always_inline bool kmsan_in_runtime(void)
 {
 	if ((hardirq_count() >> HARDIRQ_SHIFT) > 1)
 		return true;
+	if (in_nmi())
+		return true;
 	return kmsan_get_context()->kmsan_in_runtime;
 }