------------[ cut here ]------------
WARNING: CPU: 1 PID: 3280 at kernel/signal.c:334 task_participate_group_stop+0x224/0x2d0 kernel/signal.c:334
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3280 Comm: syz-executor0 Not tainted 4.9.57-gf8de76a #68
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801cd207a20 ffffffff81d93cf9 ffffffff83a46b40 ffff8801cd207af8
 ffffffff83a4d600 ffffffff8115d5a4 0000000000000009 ffff8801cd207ae8
 ffffffff8142ecd1 0000000041b58ab3 ffffffff841859b8 ffffffff8142eb15
Call Trace:
 [<ffffffff81d93cf9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d93cf9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8142ecd1>] panic+0x1bc/0x3a8 kernel/panic.c:179
 [<ffffffff811321d4>] __warn+0x1c4/0x1e0 kernel/panic.c:542
 [<ffffffff8113243c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff8115d5a4>] task_participate_group_stop+0x224/0x2d0 kernel/signal.c:334
 [<ffffffff81161bfb>] do_signal_stop+0x19b/0x7b0 kernel/signal.c:2022
 [<ffffffff8116661c>] get_signal+0x4bc/0x1600 kernel/signal.c:2278
 [<ffffffff81052c87>] do_signal+0x87/0x1960 arch/x86/kernel/signal.c:807
 [<ffffffff81003a35>] exit_to_usermode_loop+0xe5/0x130 arch/x86/entry/common.c:156
 [<ffffffff81006350>] prepare_exit_to_usermode arch/x86/entry/common.c:190 [inline]
 [<ffffffff81006350>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
 [<ffffffff838ad166>] entry_SYSCALL_64_fastpath+0xc4/0xc6