linux-kernel - Re: [PATCH 25/26] isdn: eicon: mark divascapi incompatible with kasan

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Date:   Fri, 3 Mar 2017 16:37:20 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     kasan-dev <kasan-dev@...glegroups.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Networking <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-media@...r.kernel.org,
        linux-wireless <linux-wireless@...r.kernel.org>,
        kernel-build-reports@...ts.linaro.org,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH 25/26] isdn: eicon: mark divascapi incompatible with kasan

On Fri, Mar 3, 2017 at 4:22 PM, Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:
> On 03/03/2017 05:54 PM, Arnd Bergmann wrote:
>> On Fri, Mar 3, 2017 at 3:20 PM, Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:
>>> On 03/02/2017 07:38 PM, Arnd Bergmann wrote:
>>>
>>> This is kinda radical solution.
>>> Wouldn't be better to just increase -Wframe-larger-than for this driver through Makefile?
>>
>> I thought about it too, and decided for disabling the driver entirely
>> since I suspected that
>> not only the per-function stack frame is overly large here but also
>> depth of the call chain,
>> which would then lead us to hiding an actual stack overflow.
>>
>
> No one complained so far ;)
> Disabling the driver like you did will throw it out from allmodconfig so it will receive less compile-testing.

Good point, I'll add a driver specific flag then and leave it there.

>> Note that this driver is almost certainly broken, it hasn't seen any
>> updates other than
>> style and compile-warning fixes in 10 years and doesn't support any of
>> the hardware
>> introduced since 2002 (the company still makes PCIe ISDN adapters, but
>> the driver
>> only supports legacy PCI versions and older buses).
>
> Which means that it's unlikely that someone will run this driver with KASAN
and trigger stack overflow (if it's really possible).

True.

   Arnd