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

[Guenter Roeck]

On 2/13/23 11:51, Kees Cook wrote:
> On February 12, 2023 4:35:46 PM PST, Guenter Roeck <linux@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >
> > 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