linux-kernel - Re: general protection fault in __handle_mm

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Date:   Tue, 9 Oct 2018 12:02:58 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     aneesh.kumar@...ux.ibm.com,
        syzbot+1577fbe983d20fe2e88f@...kaller.appspotmail.com,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        LKML <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kirill.shutemov@...ux.intel.com
Subject: Re: general protection fault in __handle_mm_fault

On Tue, Oct 9, 2018 at 11:00 AM Eric Dumazet <eric.dumazet@...il.com> wrote:
>
>
>
> On 10/09/2018 01:53 AM, Aneesh Kumar K.V wrote:
> ...
>
> >>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13cdb67e400000
> ...
>
> >
> > Can you check with this patch

Thanks. With that patch the crash indeed does not occur.

>
> Well, this is a C repro, you can test this yourself instead of asking Willem who
> already did a painful bisection.

Thanks Eric. It does take some effort to get the syzkaller environment
up and running [1] and I happen to have it ready, so I don't mind testing
a few patches.

It just had to wait until I got to the office. Somehow the debug kernel
produces so much output that it consistently locked up my shell over ssh.

[1] for reference:
https://github.com/google/syzkaller/blob/master/docs/linux/setup_ubuntu-host_qemu-vm_x86-64-kernel.md