linux-kernel - Re: bpf-next boot error: KASAN: use-after-free Write in call_usermodehelper_exec

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Message-ID: <CACT4Y+ZzSfCvYaGwbz2Y_5DfpeBOfm621is_hQWik119VGOERg@mail.gmail.com>
Date:   Thu, 7 Jun 2018 20:32:27 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        syzbot <syzbot+2c73319c406f1987d156@...kaller.appspotmail.com>,
        Alexei Starovoitov <ast@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: bpf-next boot error: KASAN: use-after-free Write in call_usermodehelper_exec_work

On Thu, Jun 7, 2018 at 8:12 PM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
>> > <syzbot+2c73319c406f1987d156@...kaller.appspotmail.com> wrote:
>> > > Hello,
>> > >
>> > > syzbot found the following crash on:
>> > >
>> > > HEAD commit:    69b450789136 Merge branch 'misc-BPF-improvements'
>> > > git tree:       bpf-next
>> > > console output: https://syzkaller.appspot.com/x/log.txt?x=1080d1d7800000
>> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=e4078980b886800c
>> > > dashboard link: https://syzkaller.appspot.com/bug?extid=2c73319c406f1987d156
>> > > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>> > >
>> > > Unfortunately, I don't have any reproducer for this crash yet.
>> > >
>> > > IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> > > Reported-by: syzbot+2c73319c406f1987d156@...kaller.appspotmail.com
>> >
>> >
>> > This crash now happens on every other boot of mainline tree. This
>> > prevents syzbot testing of new code, and just boots machine with
>> > corrupted memory. Were there any recent changes in umh? +Alexei, you
>> > seem to touch it last. Could your change cause this?
>>
>> looking into it. I think I see the issue. Trying to reproduce.
>
> And this is why a test driver would be useful ;)

And also testing everything with KASAN and LOCKDEP ;)