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From:   Jamal Hadi Salim <jhs@mojatatu.com>
Date:   Thu, 8 Jun 2023 12:40:09 -0400
Message-ID: <CAM0EoM=osXFK7FLzF2QB3PvZ+W4sr=pnPD5jG1FjrzSbw-emWQ@mail.gmail.com>
Subject: Re: [PATCH v2 1/1] net/sched: cls_u32: Fix reference counter leak
 leading to overflow
To:     Lee Jones <lee@kernel.org>
Cc:     Eric Dumazet <edumazet@google.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
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On Thu, Jun 8, 2023 at 3:47=E2=80=AFAM Lee Jones <lee@kernel.org> wrote:
>
> On Thu, 08 Jun 2023, Eric Dumazet wrote:
>
> > On Thu, Jun 8, 2023 at 9:29=E2=80=AFAM 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'.
> > >
> > > In order to prevent this, move the point of possible failure above th=
e
> > > point where the reference counter is incremented.  Also save any
> > > meaningful return values to be applied to the return data at the
> > > appropriate point in time.
> > >
> > > This issue was caught with KASAN.
> > >
> > > Fixes: 705c7091262d ("net: sched: cls_u32: no need to call tcf_exts_c=
hange for newly allocated struct")
> > > Suggested-by: Eric Dumazet <edumazet@google.com>
> > > Signed-off-by: Lee Jones <lee@kernel.org>
> > > ---
> >
> > Thanks Lee !
>
> No problem.  Thanks for your help.
>
> > Reviewed-by: Eric Dumazet <edumazet@google.com>

Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>

cheers,
jamal

> --
> Lee Jones [=E6=9D=8E=E7=90=BC=E6=96=AF]