Re: [PATCH v2] acpi: acpica: fix acpi operand cache leak

[Seunghun Han]

Hi, Rafael.

I added my opinion below.

2017-02-24 20:50 GMT+09:00 Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>:
> On Friday, February 24, 2017 08:52:42 PM Seunghun Han wrote:
>> Hi, Lv Zheng.
>>
>> I added my handcrafted ACPI table under your request, because
>> "acpidump -c on" and "acpidump -c off" doesn't work.
>>
>> 2017-02-21 19:36 GMT+09:00 Seunghun Han <kkamagui@xxxxxxxxx>:
>> > Hello,
>> >
>> > I attached the test results below,
>> >
>> > 2017-02-21 9:53 GMT+09:00 Rowafael J. Wysocki <rjw@xxxxxxxxxxxxx>:
>> >> On Tuesday, February 21, 2017 12:33:08 AM Zheng, Lv wrote:
>> >>> Hi,
>> >>>
>> >>> > From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi-owner@xxxxxxxxxxxxxxx] On Behalf Of Seunghun
>> >>> > Han
>> >>> > Subject: [PATCH v2] acpi: acpica: fix acpi operand cache leak
>> >>> >
>> >>> > I'm Seunghun Han, and I work for National Security Research Institute of
>> >>> > South Korea.
>> >>> >
>> >>> > I have been doing a research on ACPI and making a handcrafted ACPI table
>> >>> > for my research.
>> >>> > Errors of handcrafted ACPI tables are handled well in Linux kernel while boot
>> >>> > process, and Linux kernel goes well without critical problems.
>> >>> > But I found some ACPI operand cache leaks in ACPI early abort cases.
>> >>> >
>> >>> > Boot log of ACPI operand cache leak is as follows:
>> >>> > >[    0.174332] ACPI: Added _OSI(Module Device)
>> >>> > >[    0.175504] ACPI: Added _OSI(Processor Device)
>> >>> > >[    0.176010] ACPI: Added _OSI(3.0 _SCP Extensions)
>> >>> > >[    0.177032] ACPI: Added _OSI(Processor Aggregator Device)
>> >>> > >[    0.178284] ACPI: SCI (IRQ16705) allocation failed
>> >>> > >[    0.179352] ACPI Exception: AE_NOT_ACQUIRED, Unable to install System Control Interrupt handler
>> >>> > (20160930/evevent-131)
>> >>> > >[    0.180008] ACPI: Unable to start the ACPI Interpreter
>> >>> > >[    0.181125] ACPI Error: Could not remove SCI handler (20160930/evmisc-281)
>> >>> > >[    0.184068] kmem_cache_destroy Acpi-Operand: Slab cache still has objects
>> >>> > >[    0.185358] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.10.0-rc3 #2
>> >>> > >[    0.186820] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
>> >>> > >[    0.188000] Call Trace:
>> >>> > >[    0.188000]  ? dump_stack+0x5c/0x7d
>> >>> > >[    0.188000]  ? kmem_cache_destroy+0x224/0x230
>> >>> > >[    0.188000]  ? acpi_sleep_proc_init+0x22/0x22
>> >>> > >[    0.188000]  ? acpi_os_delete_cache+0xa/0xd
>> >>> > >[    0.188000]  ? acpi_ut_delete_caches+0x3f/0x7b
>> >>> > >[    0.188000]  ? acpi_terminate+0x5/0xf
>> >>> > >[    0.188000]  ? acpi_init+0x288/0x32e
>> >>> > >[    0.188000]  ? __class_create+0x4c/0x80
>> >>> > >[    0.188000]  ? video_setup+0x7a/0x7a
>> >>> > >[    0.188000]  ? do_one_initcall+0x4e/0x1b0
>> >>> > >[    0.188000]  ? kernel_init_freeable+0x194/0x21a
>> >>> > >[    0.188000]  ? rest_init+0x80/0x80
>> >>> > >[    0.188000]  ? kernel_init+0xa/0x100
>> >>> > >[    0.188000]  ? ret_from_fork+0x25/0x30
>> >>>
>> >>> I'm more interested in the way of triggering AE_NOT_ACQUIRED error.
>> >>> So could you send us the handcrafted ACPI table or both the "acpidump -c on" and "acpidump -c off" output?
>>
>> I modified FACP, FACS, APIC table in VirtualBox for Linux.
>> Here are raw dumps of table.
>
> So, excuse me, but what's the security issue here?
>
> You hacked your ACPI tables into pieces which requires root privileges anyway.
>
> Thanks,
> Rafael
>

As you mentioned earlier, I hacked my ACPI table for research, so it seems that
it is not a security issue.

But, if new mainboard are released and they have a vendor-specific ACPI table
which has invalid data, the old version of kernel (<=4.9) will possibly expose
kernel address and KASLR will be neutralized unintentionally.

I know the vendors collaborate with Linux kernel developers, but the problem
can still occur.

Hardware vendors release so many kinds of mainboard in a year, and the major
Linux distros (Ubuntu, Fedora, etc.) will have 4.8 kernel for a long time.

For this reason, I think this issue has a security aspect.

Thank you.

Best regards.