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

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Message-Id: <20170714.105431.403659291323482633.davem@davemloft.net>
Date:   Fri, 14 Jul 2017 10:54:31 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     glider@...gle.com
Cc:     dvyukov@...gle.com, kcc@...gle.com, edumazet@...gle.com,
        lucien.xin@...il.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2] sctp: don't dereference ptr before leaving
 _sctp_walk_{params,errors}()

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.