netdev - Re: KASAN: use-after-free Read in fib6

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Message-ID: <20180119131949.GA19786@splinter>
Date:   Fri, 19 Jan 2018 15:19:50 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     syzbot <syzbot+22b2e8ffdc35d97b5942@...kaller.appspotmail.com>
Cc:     davem@...emloft.net, kuznet@....inr.ac.ru,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, yoshfuji@...ux-ipv6.org,
        weiwan@...gle.com
Subject: Re: KASAN: use-after-free Read in fib6_ifup (2)

On Thu, Jan 18, 2018 at 09:58:01PM -0800, syzbot wrote:
> Hello,
> 
> syzbot hit the following crash on net-next commit
> 564737f981fb4b4b3266901508bb9b90d9d43de8
> 
> So far this crash happened 18 times on mmots, net-next.
> C reproducer is attached.
> syzkaller reproducer is attached.
> Raw console output is attached.
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+22b2e8ffdc35d97b5942@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
> 
> device lo entered promiscuous mode
> device lo left promiscuous mode
> device lo entered promiscuous mode
> ==================================================================
> BUG: KASAN: use-after-free in fib6_ifup+0x212/0x220 net/ipv6/route.c:3573

After applying Wei's recent commit 7f8e6b09f32d ("ipv6: don't let
tb6_root node share routes with other node") on top of net-next I can no
longer reproduce the issue with the provided reproducer (repro.syz.txt).

Will try to understand the exact reason for the bug before marking this
as fixed.