netdev - Re: [v4.12 regression] netns: NULL deref in fib_sync_down

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Message-ID: <20170728180437.s4pwdyguihmgjrjp@qmqm.qmqm.pl>
Date:   Fri, 28 Jul 2017 20:04:37 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [v4.12 regression] netns: NULL deref in fib_sync_down_dev()

On Fri, Jul 28, 2017 at 08:36:02PM +0300, Ido Schimmel wrote:
> On Fri, Jul 28, 2017 at 10:28:16AM -0700, Cong Wang wrote:
> > On Fri, Jul 28, 2017 at 9:43 AM, Ido Schimmel <idosch@...sch.org> wrote:
> > > On Fri, Jul 28, 2017 at 06:00:47PM +0200, Michał Mirosław wrote:
> > >> Dear NetDevs,
> > >>
> > >> Before I go to bisecting, have you seen a following NULL dereference,
> > >> yet?  Where should I start looking?  It is triggered by deleting netns
> > >> (cut-down script attached - triggers every time).  This was working
> > >> correctly under v4.11.x.
> > > Thanks for the report. I just reproduced this on my system. I believe
> > > the problem is a missing NULL check for 'in_dev' in
> > > call_fib_nh_notifiers(). I'll test a fix.
> > But your commit 982acb97560c8118c2109504a22b0d78a580547d
> > is merged in v4.11-rc1. How could 4.11.x work correctly?
> It doesn't. I just reproduced this on v4.11.

Thanks for looking into this.  I was sure that I ran v4.11.7 last time,
but it turns out I worked on this earlier than that.  I'll be glad to
test patches for this issue when you have it.

Best Regards,
Michał Mirosław