Re: [PATCH] ipv4/mptcp: fix divide error

[Mat Martineau]

On Tue, 24 Aug 2021, Jiang Biao wrote:

> Hi,
>
> On Tue, 24 Aug 2021 at 15:36, Matthieu Baerts
> <matthieu.baerts@xxxxxxxxxxxx> 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


Thanks!

--
Mat Martineau
Intel