linux-kernel - RE: [PATCH] ACPICA: fix UBSAN warning using __builtin

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Message-ID: <BYAPR11MB30969737340044437013BF44F08B0@BYAPR11MB3096.namprd11.prod.outlook.com>
Date:   Tue, 2 Jun 2020 00:02:57 +0000
From:   "Kaneda, Erik" <erik.kaneda@...el.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        "Moore, Robert" <robert.moore@...el.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>
CC:     Ard Biesheuvel <ardb@...nel.org>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "glider@...gle.com" <glider@...gle.com>,
        "guohanjun@...wei.com" <guohanjun@...wei.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "pcc@...gle.com" <pcc@...gle.com>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "will@...nel.org" <will@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>
Subject: RE: [PATCH] ACPICA: fix UBSAN warning using __builtin_offsetof



> -----Original Message-----
> From: Nick Desaulniers <ndesaulniers@...gle.com>
> Sent: Monday, June 1, 2020 4:18 PM
> To: Moore, Robert <robert.moore@...el.com>; Kaneda, Erik
> <erik.kaneda@...el.com>; Wysocki, Rafael J <rafael.j.wysocki@...el.com>;
> Len Brown <lenb@...nel.org>
> Cc: Ard Biesheuvel <ardb@...nel.org>; dvyukov@...gle.com;
> glider@...gle.com; guohanjun@...wei.com; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> lorenzo.pieralisi@....com; mark.rutland@....com;
> ndesaulniers@...gle.com; pcc@...gle.com; rjw@...ysocki.net;
> will@...nel.org; stable@...r.kernel.org; linux-acpi@...r.kernel.org;
> devel@...ica.org
> Subject: [PATCH] ACPICA: fix UBSAN warning using __builtin_offsetof
>
Hi,
 
> 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.

I'll take a look at this tomorrow
> 
> The non-kernel runtime of UBSAN would print:
> runtime error: member access within null pointer of type for this macro.

actypes.h is owned by ACPICA so we typically do not allow compiler-specific
extensions because the code is intended to be compiled using the C99 standard
without compiler extensions. We could allow this sort of thing in a Linux-specific
header file like include/acpi/platform/aclinux.h but I'll take a look at the error as well..

Erik
> 
> Link: https://lore.kernel.org/lkml/20200521100952.GA5360@willie-the-truck/
> Cc: stable@...r.kernel.org
> Reported-by: Will Deacon <will@...nel.org>
> Suggested-by: Ard Biesheuvel <ardb@...nel.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
>  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)
>  #define ACPI_PHYSADDR_TO_PTR(i)         ACPI_TO_POINTER(i)
>  #define ACPI_PTR_TO_PHYSADDR(i)         ACPI_TO_INTEGER(i)
> 
> --
> 2.27.0.rc2.251.g90737beb825-goog