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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Wed, 16 Sep 2020 07:49:30 +0200
Message-ID: <CACT4Y+aW9DNE0_vcPypMHE9osLLyo9XxbDBxzSvLKdZSPwOe4w@mail.gmail.com>
Subject: Re: WARNING in batadv_iv_send_outstanding_bat_ogm_packet
To:     Anant Thazhemadam <anant.thazhemadam@gmail.com>
Cc:     syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        syzkaller <syzkaller@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Sep 16, 2020 at 7:43 AM Anant Thazhemadam
<anant.thazhemadam@gmail.com> wrote:
>
>
> On 16/09/20 10:25 am, Dmitry Vyukov wrote:
> > On Tue, Sep 15, 2020 at 8:34 PM Anant Thazhemadam
> > <anant.thazhemadam@gmail.com> wrote:
> >> On Monday, October 14, 2019 at 2:25:08 AM UTC+5:30 syzbot wrote:
> >>> Hello,
> >>>
> >>> syzbot found the following crash on:
> >>>
> >>> HEAD commit: da940012 Merge tag 'char-misc-5.4-rc3' of git://git.kernel..
> >>> git tree: upstream
> >>> console output: https://syzkaller.appspot.com/x/log.txt?x=13ffd808e00000
> >>> kernel config: https://syzkaller.appspot.com/x/.config?x=2d2fd92a28d3e50
> >>> dashboard link: https://syzkaller.appspot.com/bug?extid=c0b807de416427ff3dd1
> >>> compiler: clang version 9.0.0 (/home/glider/llvm/clang
> >>> 80fee25776c2fb61e74c1ecb1a523375c2500b69)
> >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=141ffd77600000
> >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11edd580e00000
> >>>
> >>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> >>> Reported-by: syzbot+c0b807...@syzkaller.appspotmail.com
> >>>
> >>> ------------[ cut here ]------------
> >>> WARNING: CPU: 1 PID: 30 at net/batman-adv/bat_iv_ogm.c:382
> >>> batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:382 [inline]
> >>> WARNING: CPU: 1 PID: 30 at net/batman-adv/bat_iv_ogm.c:382
> >>> batadv_iv_send_outstanding_bat_ogm_packet+0x6b4/0x770
> >>> net/batman-adv/bat_iv_ogm.c:1663
> >>> Kernel panic - not syncing: panic_on_warn set ...
> >>> CPU: 1 PID: 30 Comm: kworker/u4:2 Not tainted 5.4.0-rc2+ #0
> >>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> >>> Google 01/01/2011
> >>> Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
> >>> Call Trace:
> >>> __dump_stack lib/dump_stack.c:77 [inline]
> >>> dump_stack+0x1d8/0x2f8 lib/dump_stack.c:113
> >>> panic+0x264/0x7a9 kernel/panic.c:221
> >>> __warn+0x20e/0x210 kernel/panic.c:582
> >>> report_bug+0x1b6/0x2f0 lib/bug.c:195
> >>> fixup_bug arch/x86/kernel/traps.c:179 [inline]
> >>> do_error_trap+0xd7/0x440 arch/x86/kernel/traps.c:272
> >>> do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:291
> >>> invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
> >>> RIP: 0010:batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:382 [inline]
> >>> RIP: 0010:batadv_iv_send_outstanding_bat_ogm_packet+0x6b4/0x770
> >>> net/batman-adv/bat_iv_ogm.c:1663
> >>> Code: 66 05 00 eb 05 e8 9c 48 23 fa 48 83 c4 68 5b 41 5c 41 5d 41 5e 41 5f
> >>> 5d c3 e8 88 48 23 fa 0f 0b e9 34 ff ff ff e8 7c 48 23 fa <0f> 0b e9 28 ff
> >>> ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c c1 f9 ff
> >>> RSP: 0018:ffff8880a9abfc48 EFLAGS: 00010293
> >>> RAX: ffffffff874fe8a4 RBX: ffff888094160870 RCX: ffff8880a9ab2080
> >>> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
> >>> RBP: ffff8880a9abfcd8 R08: ffffffff874fe28e R09: ffffed10123e6969
> >>> R10: ffffed10123e6969 R11: 0000000000000000 R12: ffff888091f34000
> >>> R13: dffffc0000000000 R14: ffff8880a80c5000 R15: ffff8880a4481400
> >>> process_one_work+0x7ef/0x10e0 kernel/workqueue.c:2269
> >>> worker_thread+0xc01/0x1630 kernel/workqueue.c:2415
> >>> kthread+0x332/0x350 kernel/kthread.c:255
> >>> ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> >>> Kernel Offset: disabled
> >>> Rebooting in 86400 seconds..
> >>>
> >>>
> >>> ---
> >>> This bug is generated by a bot. It may contain errors.
> >>> See https://goo.gl/tpsmEJ for more information about syzbot.
> >>> syzbot engineers can be reached at syzk...@googlegroups.com.
> >>>
> >>> syzbot will keep track of this bug report. See:
> >>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >>> syzbot can test patches for this bug, for details see:
> >>> https://goo.gl/tpsmEJ#testing-patches
> >>
> >> For this bug, syzbot does not seem to be able to build the kernel anymore.
> >> Can bugs like these be considered and closed as invalid?
> >>
> >> Thanks,
> >> Anant
> > Hi Anant,
> >
> > +syzkaler, lkml (nobody is generally reading syzkaller-bugs).
> >
> > What do you mean by "not able to build a kernel for this bug"?
> > Building a kernel is not related to a particular bug. It's the same
> > for all bugs...
>
> Hi,
>
> I thought this might be a query that's better suited for the syzkaller groups,
> and hence posted it on there.
>
> I wanted to check if this bug was still present and relevant, so I tried to check
> by sending a syz test request for the upstream kernel (the dashboard shows
> that the error was found in the upstream kernel).
>
> However, I was notified later that the build/boot had failed.
> Feel free to correct me if I'm wrong, but I doubt that the reason build/boot
> had failed, was because of the bug itself (the error report is visible on the
> bug's dashboard page itself).
>
> I wanted to know what was the typical protocol in cases like this. Would this be
> a valid reason enough to close the bug as invalid? Or is there something else
> that can be done, to indicate that the upstream kernel doesn't even build/boot
> for this bug to be tested anymore?
> If nothing else, how else can I try and get syzbot to test if this bug still exists or
> not?
>
> Thanks,
> Anant


I see that config is not building anymore:

BTF: .tmp_vmlinux.btf: pahole version v1.9 is too old, need at least v1.16
Failed to generate BTF for vmlinux
Try to disable CONFIG_DEBUG_INFO_BTF
Makefile:1162: recipe for target 'vmlinux' failed

This is not anyhow top the bug itself, if it still happens or not. So
this does not look like a valid reason to close the bug.

There are two options:
1. Attach a patch for testing that disables CONFIG_DEBUG_INFO_BTF
(e.g. delete it, or make it dependent on some disabled config, not
sure what's the easiest working option).
2. Test locally with the config disabled.