netdev - Re:Re: [net PATCH] net: sched: Fix one possible panic when no destroy callback

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Date:   Wed, 28 Jun 2017 08:54:53 +0800 (CST)
From:   "Gao Feng" <gfree.wind@....163.com>
To:     "Eric Dumazet" <eric.dumazet@...il.com>
Cc:     "Cong Wang" <xiyou.wangcong@...il.com>,
        "Jamal Hadi Salim" <jhs@...atatu.com>,
        "Jiri Pirko" <jiri@...nulli.us>,
        "David Miller" <davem@...emloft.net>,
        "Linux Kernel Network Developers" <netdev@...r.kernel.org>
Subject: Re:Re: [net PATCH] net: sched: Fix one possible panic when no
 destroy callback

At 2017-06-28 01:49:50, "Eric Dumazet" <eric.dumazet@...il.com> wrote:
>On Tue, 2017-06-27 at 10:08 -0700, Cong Wang wrote:
>> On Tue, Jun 27, 2017 at 9:50 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> > On Tue, 2017-06-27 at 09:30 -0700, Cong Wang wrote:
>> >> On Mon, Jun 26, 2017 at 6:35 PM,  <gfree.wind@....163.com> wrote:
>> >> > From: Gao Feng <gfree.wind@....163.com>
>> >> >
>> >> > When qdisc fail to init, qdisc_create would invoke the destroy callback
>> >> > to cleanup. But there is no check if the callback exists really. So it
>> >> > would cause the panic if there is no real destroy callback like these
>> >> > qdisc codel, pfifo, pfifo_fast, and so on.
>> >> >
>> >> > Now add one the check for destroy to avoid the possible panic.
>> >> >
>> >> > Signed-off-by: Gao Feng <gfree.wind@....163.com>
>> >>
>> >> Looks good,
>> >>
>> >> Acked-by: Cong Wang <xiyou.wangcong@...il.com>
>> >>
>> >> This is introduced by commit 87b60cfacf9f17cf71933c6e33b.
>> >> Please add proper Fixes tag next time.

OK. Actually I didn't know it is introduced by this commit before :)
Need I send an update patch again ?

>> >
>> > Given that pfifo, pfifo_fast or codel can not fail their init,
>> 
>> 
>> How about codel_init() -> codel_change() -> nla_parse_nested() ?
>
>
>Yeah, with a malicious user space then (iproute2/tc is fine), codel
>could be problematic.
>
>pfifo and pfifo_fast can definitely not hit this bug.
>
>changelog needs a bit of attention, even if the bug is real.
>
>Thanks.
>
>

Yes, the codel could fail to init, and the fifo/pfifo could failed When "nla_len(opt) < sizeof(*ctl)".

Best Regards
Feng