linux-kernel - Re: KASAN: use-after-free Read in update_blocked

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Date:   Thu, 21 Mar 2019 07:01:26 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+0dbf864d3b52555e8265@...kaller.appspotmail.com>
Cc:     David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Stefano Brivio <sbrivio@...hat.com>,
        Sabrina Dubroca <sd@...asysnail.net>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: KASAN: use-after-free Read in update_blocked_averages

On Thu, Mar 21, 2019 at 4:34 AM syzbot
<syzbot+0dbf864d3b52555e8265@...kaller.appspotmail.com> wrote:
>
> syzbot has bisected this bug to:
>
> commit b8a51b38e4d4dec3e379d52c0fe1a66827f7cf1e
> Author: Stefano Brivio <sbrivio@...hat.com>
> Date:   Thu Nov 8 11:19:23 2018 +0000
>
>      fou, fou6: ICMP error handlers for FoU and GUE
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11e33c17200000
> start commit:   b8a51b38 fou, fou6: ICMP error handlers for FoU and GUE
> git tree:       net-next
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=13e33c17200000
> console output: https://syzkaller.appspot.com/x/log.txt?x=15e33c17200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=dcbea7daf3ea3e3e
> dashboard link: https://syzkaller.appspot.com/bug?extid=0dbf864d3b52555e8265
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=137ae6d5400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15dbd77b400000
>
> Reported-by: syzbot+0dbf864d3b52555e8265@...kaller.appspotmail.com
> Fixes: b8a51b38 ("fou, fou6: ICMP error handlers for FoU and GUE")

That commit caused lots of crashes that look completely differently.
Now all that is fixed. The last crash for this bugs happened 2+ months
ago. So let's just do:

#syz fix:
fou: Prevent unbounded recursion in GUE error handler also with UDP-Lite