netdev - Re: [PATCH net] net: sched: fix use-after-free in tc_new

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Message-ID: <CANn89iL7_FtnUmTxY=tN5dQuB82QL=LANXKxo+vwO90yu1fcJg@mail.gmail.com>
Date:   Mon, 31 Jan 2022 11:31:26 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Vlad Buslov <vladbu@...dia.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Vlad Buslov <vladbu@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] net: sched: fix use-after-free in tc_new_tfilter()

On Mon, Jan 31, 2022 at 11:28 AM Vlad Buslov <vladbu@...dia.com> wrote:
>
> Yeah, but I also didn't get how the "chain" variable can get reused in
> that other function (tcf_new_tfilter()). It seems to always be
> unconditionally assigned with return value of tcf_chain_get().
>

This is why I removed the chain=NULL initialization which is not needed.

The potential issue about replay was really about @q variable.