netdev - Re: [PATCH 3/5] net: sched: taprio: Fix null pointer deref bug

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Message-ID: <CAM_iQpVCvdbiuHpeskFyJJmHMZdmPuf4G1QAVntUu_FjNK6vVg@mail.gmail.com>
Date:   Mon, 22 Apr 2019 11:07:04 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Andre Guedes <andre.guedes@...el.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>
Subject: Re: [PATCH 3/5] net: sched: taprio: Fix null pointer deref bug

On Mon, Apr 22, 2019 at 11:04 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Fri, Apr 19, 2019 at 6:06 PM Andre Guedes <andre.guedes@...el.com> wrote:
> >
> > If 'entry' is NULL we WARN_ON() but dereference the pointer anyway,
> > generating a null pointer dereference bug. This patch fixes should_
> > restart_cycle() so we return if the pointer is NULL.
>
> Hmm, while you are on it, how is it possible to have entry==NULL
> for should_restart_cycle(). It is only called in advance_sched()
> where entry is already checked against NULL right before it,
> so for me, entry is always NULL at the point of calling
> should_restart_cycle().

I meant, 'entry' is always non-NULL here... I typed too fast.