------------[ cut here ]------------
!valid_signal(sig)
WARNING: kernel/signal.c:2174 at do_notify_parent+0xea8/0x10b0 kernel/signal.c:2174, CPU#0: syz.3.20/5978
Modules linked in:
CPU: 0 UID: 0 PID: 5978 Comm: syz.3.20 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:do_notify_parent+0xea8/0x10b0 kernel/signal.c:2174
Code: f4 ff ff e8 ba de 3d 00 41 c1 ff 08 c7 84 24 90 00 00 00 01 00 00 00 44 89 bc 24 a0 00 00 00 e9 92 f8 ff ff e8 99 de 3d 00 90 <0f> 0b 90 45 31 f6 e9 f5 f9 ff ff e8 88 de 3d 00 90 0f 0b 90 e9 43
RSP: 0000:ffffc9000386faa8 EFLAGS: 00010093
RAX: 0000000000000000 RBX: ffff888035940000 RCX: ffffffff81ca9f1b
RDX: ffff888035940000 RSI: ffffffff81caad07 RDI: ffff888035940000
RBP: 0000000000000080 R08: 0000000000000007 R09: 0000000000000040
R10: 0000000000000080 R11: 0000000000000000 R12: 1ffff9200070df58
R13: dffffc0000000000 R14: 0000000000000080 R15: ffff888035e5ca00
FS:  0000000000000000(0000) GS:ffff8880d6379000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000300 CR3: 000000000e596000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 exit_notify kernel/exit.c:757 [inline]
 do_exit+0x1b05/0x2a60 kernel/exit.c:987
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1117
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3037
 arch_do_signal_or_restart+0x91/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:98 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:252 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:323 [inline]
 irqentry_exit+0x403/0x790 kernel/entry/common.c:162
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 002b:0000200000000108 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007fdc23815fa0 RCX: 00007fdc2359cdd9
RDX: 0000200000000200 RSI: 0000200000000100 RDI: 0000000081000080
RBP: 00007fdc23632d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007fdc23815fac R14: 00007fdc23815fa0 R15: 00007fdc23815fa0
 </TASK>