------------[ 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 4.9.60-gdfe0a9b #81
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d1df7ae0 ffffffff81d91389 ffffffff83a46ba0 ffff8801d1df7bb8
 ffffffff83a4d600 ffffffff8115d564 0000000000000009 ffff8801d1df7ba8
 ffffffff8142e391 0000000041b58ab3 ffffffff84185bc8 ffffffff8142e1d5
Call Trace:
 [<ffffffff81d91389>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d91389>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8142e391>] panic+0x1bc/0x3a8 kernel/panic.c:179
 [<ffffffff811321e4>] __warn+0x1c4/0x1e0 kernel/panic.c:542
 [<ffffffff8113244c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff8115d564>] task_participate_group_stop+0x224/0x2d0 kernel/signal.c:334
 [<ffffffff81161bbb>] do_signal_stop+0x19b/0x7b0 kernel/signal.c:2022
 [<ffffffff81166540>] get_signal+0x430/0x14e0 kernel/signal.c:2278
 [<ffffffff81052c87>] do_signal+0x87/0x1960 arch/x86/kernel/signal.c:807
 [<ffffffff81003a31>] exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:156
 [<ffffffff81006340>] prepare_exit_to_usermode arch/x86/entry/common.c:190 [inline]
 [<ffffffff81006340>] syscall_return_slowpath+0x1a0/0x1e0 arch/x86/entry/common.c:259
 [<ffffffff838aa3a6>] entry_SYSCALL_64_fastpath+0xc4/0xc6