WARNING in batadv_iv_send_outstanding_bat_ogm_packet

[syzbot]

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..


---
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[syzbot]

syzbot has bisected this bug to:

commit 26d051e301f67cdd2ea3404abb43902f13214efa
Author: Arvind Yadav <arvind....@gmail.com>
Date: Thu Jun 29 08:21:35 2017 +0000

media: exynos4-is: fimc-is-i2c: constify dev_pm_ops structures

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10a0aff0e00000
start commit: da940012 Merge tag 'char-misc-5.4-rc3' of git://git.kernel..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=12a0aff0e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14a0aff0e00000

kernel config: https://syzkaller.appspot.com/x/.config?x=2d2fd92a28d3e50
dashboard link: https://syzkaller.appspot.com/bug?extid=c0b807de416427ff3dd1

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=141ffd77600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11edd580e00000

Reported-by: syzbot+c0b807...@syzkaller.appspotmail.com
Fixes: 26d051e301f6 ("media: exynos4-is: fimc-is-i2c: constify dev_pm_ops
structures")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Anant Thazhemadam]

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

[Dmitry Vyukov]

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...

[Anant Thazhemadam]

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

[Dmitry Vyukov]

On Wed, Sep 16, 2020 at 7:43 AM Anant Thazhemadam

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.