linux-kernel - Re: [PATCH v2] sctp: don't dereference ptr before leaving _sctp_walk

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Message-ID: <CAG_fn=WX+ahhp8tokB5K59Q-0z4ok4g+8TMOknTENf2yuvn_1g@mail.gmail.com>
Date:   Mon, 17 Jul 2017 11:37:37 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     David Miller <davem@...emloft.net>
Cc:     Dmitriy Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        lucien xin <lucien.xin@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] sctp: don't dereference ptr before leaving _sctp_walk_{params,errors}()

On Fri, Jul 14, 2017 at 7:54 PM, David Miller <davem@...emloft.net> wrote:
> From: Alexander Potapenko <glider@...gle.com>
> Date: Fri, 14 Jul 2017 19:33:54 +0200
>
>> On Fri, Jul 14, 2017 at 7:23 PM, David Miller <davem@...emloft.net> wrote:
>>> From: Alexander Potapenko <glider@...gle.com>
>>> Date: Fri, 14 Jul 2017 18:33:01 +0200
>>>
>>>> On Fri, Jul 14, 2017 at 5:58 PM, David Miller <davem@...emloft.net> wrote:
>>>>> From: Alexander Potapenko <glider@...gle.com>
>>>>> Date: Fri, 14 Jul 2017 12:03:29 +0200
>>>>>
>>>>>>  v2: per comment from David Miller, make sure the whole iterator->length
>>>>>>      fits into the remaining buffer.
>>>>>
>>>>> Please compile and functionally test your changes:
>>>>>
>>>>> In file included from ./include/linux/compiler.h:58:0,
>>>>>                  from ./include/uapi/linux/stddef.h:1,
>>>>>                  from ./include/linux/stddef.h:4,
>>>>>                  from ./include/uapi/linux/posix_types.h:4,
>>>>>                  from ./include/uapi/linux/types.h:13,
>>>>>                  from ./include/linux/types.h:5,
>>>>>                  from net/sctp/sm_statefuns.c:48:
>>>>> net/sctp/sm_statefuns.c: In function ‘sctp_sf_do_reconf’:
>>>>> ./include/net/sctp/sctp.h:472:24: error: unknown type name ‘sctp_paramhdr_t’
>>>>>       (pos.v + offsetof(sctp_paramhdr_t, length) + sizeof(pos.p->length) <\
>>>>>                         ^
>>>> Oops. Fixed.
>>>
>>> Did you functionally test the new version or just do a quick compile
>>> check and resubmit?
>> I've checked that the kernel still works, but unfortunately I couldn't
>> check whether or not this affected the uninit memory, as KMSAN
>> currently works on a fixed kernel revision. The compilation error was
>> actually caused by me failing to test the kernel when porting the fix
>> from that revision to upstream.
>>
>>> I really want you to test this if the logic has been changed.
>> Do you mean any specific tests in addition to, say, running the
>> reproducer on which the uninit use was reported?
>
> I mean the reproducer.
Yes, I've ran the reproducer, and just double-checked that. Sorry for the delay.


-- 
Alexander Potapenko
Software Engineer

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