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From:   Jiang Biao <benbjiang@gmail.com>
Date:   Mon, 30 Aug 2021 11:32:12 +0800
Message-ID: <CAPJCdBmqPgbxYTvViRQrzLgmNjQWc4PRmw_yScLgp0ktt-dVCQ@mail.gmail.com>
Subject: Re: [PATCH] ipv4/mptcp: fix divide error
To:     Mat Martineau <mathew.j.martineau@linux.intel.com>
Cc:     Matthieu Baerts <matthieu.baerts@tessares.net>,
        davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org,
        mptcp@lists.linux.dev, linux-kernel <linux-kernel@vger.kernel.org>,
        Jiang Biao <benbjiang@tencent.com>,
        Jiang Biao <tcs_robot@tencent.com>,
        Paolo Abeni <pabeni@redhat.com>
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On Thu, 26 Aug 2021 at 01:56, Mat Martineau
<mathew.j.martineau@linux.intel.com> wrote:
>
>
> On Tue, 24 Aug 2021, Jiang Biao wrote:
>
> > Hi,
> >
> > On Tue, 24 Aug 2021 at 15:36, Matthieu Baerts
> > <matthieu.baerts@tessares.net> wrote:
> >>
> >> Hi Jiang,
> >>
> >> On 24/08/2021 09:19, Jiang Biao wrote:
> >>
> >> (...)
> >>
> >>> There is a fix divide error reported,
> >>> divide error: 0000 [#1] PREEMPT SMP KASAN
> >>> RIP: 0010:tcp_tso_autosize build/../net/ipv4/tcp_output.c:1975 [inline]
> >>> RIP: 0010:tcp_tso_segs+0x14f/0x250 build/../net/ipv4/tcp_output.c:1992
> >>
> >> Thank you for this patch and validating MPTCP on your side!
> >>
> >> This issue is actively tracked on our Github project [1] and a patch is
> >> already in our tree [2] but still under validation.
> >>> It's introduced by non-initialized info->mss_now in __mptcp_push_pending.
> >>> Fix it by adding protection in mptcp_push_release.
> >>
> >> Indeed, you are right, info->mss_now can be set to 0 in some cases but
> >> that's not normal.
> >>
> >> Instead of adding a protection here, we preferred fixing the root cause,
> >> see [2]. Do not hesitate to have a look at the other patch and comment
> >> there if you don't agree with this version.
> >> Except if [2] is difficult to backport, I think we don't need your extra
> >> protection. WDYT?
> >>
> > Agreed, fixing the root cause is much better.
> > Thanks for the reply.
> >
>
> Hi Jiang -
>
> Could you try cherry-picking this commit to see if it eliminates the error
> in your system?
>
> https://github.com/multipath-tcp/mptcp_net-next/commit/9ef5aea5a794f4a369e26ed816e9c80cdc5a5f86
>
Errors' gone with the patch.:)

Regards,
Jiang
>
> Thanks!
>
> --
> Mat Martineau
> Intel