kernel panic: stack is corrupted in trace_hardirqs_off

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: e1ef035d272e Merge tag 'armsoc-defconfig' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15d59880c00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9c6a26e22579190b
dashboard link: https://syzkaller.appspot.com/bug?extid=febe5a53f698ed18109c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [linux-...@vger.kernel.org mi...@redhat.com
ros...@goodmis.org]

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+febe5a...@syzkaller.appspotmail.com

Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in:
trace_hardirqs_off+0x2cd/0x310 kernel/trace/trace_preemptirq.c:44
CPU: 1 PID: 12489 Comm: syz-executor4 Not tainted 4.20.0+ #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Dmitry Vyukov]

On Wed, Jan 2, 2019 at 12:11 PM syzbot
<syzbot+febe5a...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: e1ef035d272e Merge tag 'armsoc-defconfig' of git://git.ker..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15d59880c00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=9c6a26e22579190b
> dashboard link: https://syzkaller.appspot.com/bug?extid=febe5a53f698ed18109c
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> CC: [linux-...@vger.kernel.org mi...@redhat.com
> ros...@goodmis.org]
>
> 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+febe5a...@syzkaller.appspotmail.com

Presumably a random manifestation of the stack overflow/corruption:

#syz dup: kernel panic: stack is corrupted in udp4_lib_lookup2

See https://groups.google.com/forum/#!msg/syzkaller-bugs/vr87kmG5qRI/31nOcuVsFgAJ