syzbot

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

CPU: 0 PID: 1 Comm: init Not tainted 4.9.73-gf3f3457 #11
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801da217ae0 ffffffff81d922b9 ffffffff83a46d00 ffff8801da217bb8
 ffffffff83a4d800 ffffffff8115a9c4 0000000000000009 ffff8801da217ba8
 ffffffff8142d741 0000000041b58ab3 ffffffff84189000 ffffffff8142d585
Call Trace:
 [<ffffffff81d922b9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d922b9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8142d741>] panic+0x1bc/0x3a8 kernel/panic.c:179
 [<ffffffff8112f404>] __warn+0x1c4/0x1e0 kernel/panic.c:542
 [<ffffffff8112f66c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff8115a9c4>] task_participate_group_stop+0x224/0x2d0 kernel/signal.c:334
 [<ffffffff8115f01b>] do_signal_stop+0x19b/0x7b0 kernel/signal.c:2022
 [<ffffffff811639a0>] get_signal+0x430/0x14e0 kernel/signal.c:2278
 [<ffffffff81052c87>] do_signal+0x87/0x1a00 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
 [<ffffffff838af626>] entry_SYSCALL_64_fastpath+0xc4/0xc6
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..