linux-kernel - Re: [PATCH v2 1/1] net/sched: cls_u32: Fix reference counter leak leading to overflow

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Message-ID: <CAM0EoM=osXFK7FLzF2QB3PvZ+W4sr=pnPD5jG1FjrzSbw-emWQ@mail.gmail.com>
Date:   Thu, 8 Jun 2023 12:40:09 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Lee Jones <lee@...nel.org>
Cc:     Eric Dumazet <edumazet@...gle.com>, xiyou.wangcong@...il.com,
        jiri@...nulli.us, davem@...emloft.net, kuba@...nel.org,
        pabeni@...hat.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH v2 1/1] net/sched: cls_u32: Fix reference counter leak
 leading to overflow

On Thu, Jun 8, 2023 at 3:47 AM Lee Jones <lee@...nel.org> wrote:
>
> On Thu, 08 Jun 2023, Eric Dumazet wrote:
>
> > On Thu, Jun 8, 2023 at 9:29 AM Lee Jones <lee@...nel.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 the
> > > 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_change for newly allocated struct")
> > > Suggested-by: Eric Dumazet <edumazet@...gle.com>
> > > Signed-off-by: Lee Jones <lee@...nel.org>
> > > ---
> >
> > Thanks Lee !
>
> No problem.  Thanks for your help.
>
> > Reviewed-by: Eric Dumazet <edumazet@...gle.com>

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

cheers,
jamal

> --
> Lee Jones [李琼斯]