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Date:   Thu, 1 Jun 2023 17:48:17 +0100
From:   Lee Jones <lee@kernel.org>
To:     Eric Dumazet <edumazet@google.com>
Cc:     Jamal Hadi Salim <jhs@mojatatu.com>, xiyou.wangcong@gmail.com,
        jiri@resnulli.us, davem@davemloft.net, kuba@kernel.org,
        pabeni@redhat.com, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, stable@kernel.org
Subject: Re: [PATCH 1/1] net/sched: cls_u32: Fix reference counter leak
 leading to overflow
Message-ID: <20230601164817.GH449117@google.com>
References: <20230531141556.1637341-1-lee@kernel.org>
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On Thu, 01 Jun 2023, Eric Dumazet wrote:

> On Thu, Jun 1, 2023 at 4:06 PM Lee Jones <lee@kernel.org> wrote:
> >
> > On Wed, 31 May 2023, Jamal Hadi Salim wrote:
> >
> > > On Wed, May 31, 2023 at 11:03 AM Eric Dumazet <edumazet@google.com> wrote:
> > > >
> > > > On Wed, May 31, 2023 at 4:16 PM Lee Jones <lee@kernel.org> wrote:
> > > > >
> > > > > In the event of a failure in tcf_change_indev(), u32_set_parms() will
> > > > > immediately return without decrementing the recently incremented
> > > > > reference counter.  If this happens enough times, the counter will
> > > > > rollover and the reference freed, leading to a double free which can be
> > > > > used to do 'bad things'.
> > > > >
> > > > > Cc: stable@kernel.org # v4.14+
> > > >
> > > > Please add a Fixes: tag.
> >
> > Why?
> 
> How have you identified v4.14+ ?
> 
> Probably you did some research/"git archeology".
> 
> By adding the Fixes: tag, you allow us to double check immediately,
> and see if other bugs need to be fixed at the same time.
> 
> You can also CC blamed patch authors, to get some feedback.
> 
> Otherwise, we (people reviewing this patch) have to also do this
> research from scratch.
> 
> In this case, it seems bug was added in
> 
> commit 705c7091262d02b09eb686c24491de61bf42fdb2
> Author: Jiri Pirko <jiri@resnulli.us>
> Date:   Fri Aug 4 14:29:14 2017 +0200
> 
>     net: sched: cls_u32: no need to call tcf_exts_change for newly
> allocated struct
> 
> 
> A nice Fixes: tag would then be
> 
> Fixes: 705c7091262d ("net: sched: cls_u32: no need to call
> tcf_exts_change for newly allocated struct")

Thanks for digging this out.  I will add it.

-- 
Lee Jones [李琼斯]