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

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Date:   Tue, 27 Jun 2017 10:49:50 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     gfree.wind@....163.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: [net PATCH] net: sched: Fix one possible panic when no destroy
 callback

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.
> >
> > 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.