linux-kernel - Re: [PATCH v2] ACPICA: Replace fake flexible arrays with flexible array members

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Message-ID: <e742a790-5322-666d-5f27-33a51445bd07@roeck-us.net>
Date:   Mon, 13 Feb 2023 12:05:55 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Kees Cook <kees@...nel.org>, Kees Cook <keescook@...omium.org>
Cc:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        devel@...ica.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] ACPICA: Replace fake flexible arrays with flexible
 array members

On 2/13/23 11:51, Kees Cook wrote:
> On February 12, 2023 4:35:46 PM PST, Guenter Roeck <linux@...ck-us.net> wrote:
>> Hi,
>>
>> On Fri, Jan 27, 2023 at 11:16:25AM -0800, Kees Cook wrote:
>>> One-element arrays (and multi-element arrays being treated as
>>> dynamically sized) are deprecated[1] and are being replaced with
>>> flexible array members in support of the ongoing efforts to tighten the
>>> FORTIFY_SOURCE routines on memcpy(), correctly instrument array indexing
>>> with UBSAN_BOUNDS, and to globally enable -fstrict-flex-arrays=3.
>>>
>>> Replace one-element array with flexible-array member in struct
>>> acpi_resource_extended_irq. Replace 4-byte fixed-size array with 4-byte
>>> padding in a union with a flexible-array member in struct
>>> acpi_pci_routing_table.
>>>
>>> This results in no differences in binary output.
>>>
>>> Link: https://github.com/acpica/acpica/pull/813
>>> Signed-off-by: Kees Cook <keescook@...omium.org>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>
>> This patch results in boot failures of 32-bit images.
> 
> Weird -- I didn't see any binary differences. I'll investigate. What compiler and arch?
> 

gcc 11.3, binutils 2.39, x86 (32-bit build). This is pretty much defconfig
with ARCH=i386 and various debug options enabled.

64-bit builds do not have the problem.

Guenter

> -Kees
> 
>> Reverting it fixes the problem.
>>
>> On the failing boot tests, I see messages such as
>>
>> ACPI: \_SB_.GSIA: Enabled at IRQ 117440528
>> ERROR: Unable to locate IOAPIC for GSI 117440528
>> ahci 0000:00:1f.2: PCI INT A: failed to register GSI
>>
>> ACPI: \_SB_.GSIG: Enabled at IRQ 117440534
>> ERROR: Unable to locate IOAPIC for GSI 117440534
>> 8139cp 0000:00:02.0: PCI INT A: failed to register GSI
>>
>> Given that 117440534 == 0x7000016, that looks quite suspicious.
>> Indeed, after reverting this patch, the messages are different.
> 
> Yeah, seems like a high byte not getting cleared. Hmm.
> 
>>
>> ACPI: \_SB_.GSIA: Enabled at IRQ 16
>> ahci 0000:00:1f.2: AHCI 0001.0000 32 slots 6 ports 1.5 Gbps 0x3f impl SATA mode
>>
>> ACPI: \_SB_.GSIG: Enabled at IRQ 22
>> 8139cp 0000:00:02.0 eth0: RTL-8139C+ at 0xd0804000, 52:54:00:12:34:56, IRQ 22
>>
>> Guenter
> 
>