[PATCH] ACPICA: fix UBSAN warning using __builtin_offsetof

From: Nick Desaulniers
Date: Mon Jun 01 2020 - 19:18:22 EST

Will reported UBSAN warnings:
UBSAN: null-ptr-deref in drivers/acpi/acpica/tbfadt.c:459:37
UBSAN: null-ptr-deref in arch/arm64/kernel/smp.c:596:6

Looks like the emulated offsetof macro ACPI_OFFSET is causing these. We
can avoid this by using the compiler builtin, __builtin_offsetof.

The non-kernel runtime of UBSAN would print:
runtime error: member access within null pointer of type
for this macro.

Link: https://lore.kernel.org/lkml/20200521100952.GA5360@willie-the-truck/
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Will Deacon <will@xxxxxxxxxx>
Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
include/acpi/actypes.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
index 4defed58ea33..04359c70b198 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -508,7 +508,7 @@ typedef u64 acpi_integer;

#define ACPI_TO_POINTER(i) ACPI_CAST_PTR (void, (acpi_size) (i))
#define ACPI_TO_INTEGER(p) ACPI_PTR_DIFF (p, (void *) 0)
-#define ACPI_OFFSET(d, f) ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
+#define ACPI_OFFSET(d, f) __builtin_offsetof(d, f)