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

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Message-ID: <CAKwvOdmsCmPFiDOq7AYUyEx=60B=qo8u9yhnJDQ6nd6Ew7xDkQ@mail.gmail.com>
Date:   Tue, 2 Jun 2020 11:46:31 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     "Kaneda, Erik" <erik.kaneda@...el.com>
Cc:     "Moore, Robert" <robert.moore@...el.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>, 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

On Mon, Jun 1, 2020 at 5:03 PM Kaneda, Erik <erik.kaneda@...el.com> wrote:
>
>
> 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..

If I'm not allowed to touch that header, it looks like I can include
<linux/stddef.h> (rather than my host's <stddef.h>) to get a
definition of `offsetof` thats implemented in terms of
`__builtin_offsetof`.  I should be able to use that to replace uses of
ACPI_OFFSET.  Are any of these off limits?

$ grep -rn ACPI_OFFSET
arch/arm64/include/asm/acpi.h:34:#define ACPI_MADT_GICC_MIN_LENGTH
ACPI_OFFSET(  \
arch/arm64/include/asm/acpi.h:41:#define ACPI_MADT_GICC_SPE
(ACPI_OFFSET(struct acpi_madt_generic_interrupt, \
include/acpi/actbl.h:376:#define ACPI_FADT_OFFSET(f)             (u16)
ACPI_OFFSET (struct acpi_table_fadt, f)
drivers/acpi/acpica/acresrc.h:84:#define ACPI_RS_OFFSET(f)
  (u8) ACPI_OFFSET (struct acpi_resource,f)
drivers/acpi/acpica/acresrc.h:85:#define AML_OFFSET(f)
  (u8) ACPI_OFFSET (union aml_resource,f)
drivers/acpi/acpica/acinterp.h:17:#define ACPI_EXD_OFFSET(f)
(u8) ACPI_OFFSET (union acpi_operand_object,f)
drivers/acpi/acpica/acinterp.h:18:#define ACPI_EXD_NSOFFSET(f)
(u8) ACPI_OFFSET (struct acpi_namespace_node,f)
drivers/acpi/acpica/rsdumpinfo.c:16:#define ACPI_RSD_OFFSET(f)
 (u8) ACPI_OFFSET (union acpi_resource_data,f)
drivers/acpi/acpica/rsdumpinfo.c:17:#define ACPI_PRT_OFFSET(f)
 (u8) ACPI_OFFSET (struct acpi_pci_routing_table,f)

-- 
Thanks,
~Nick Desaulniers