------------[ cut here ]------------
!valid_signal(sig)
WARNING: kernel/signal.c:2174 at do_notify_parent+0xd18/0xe30, CPU#0: syz.9.3714/18728
Modules linked in:
CPU: 0 UID: 0 PID: 18728 Comm: syz.9.3714 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:do_notify_parent+0xd18/0xe30
Code: c6 05 10 1d 90 0e 01 48 c7 c7 e0 3a cb 8b be a3 08 00 00 48 c7 c2 60 3c cb 8b e8 83 8d 17 00 e9 2e fa ff ff e8 19 51 3b 00 90 <0f> 0b 90 45 31 e4 e9 1c ff ff ff e8 08 51 3b 00 90 0f 0b 90 e9 db
RSP: 0018:ffffc90009d0fbe0 EFLAGS: 00010093
RAX: ffffffff818a5bd7 RBX: dffffc0000000000 RCX: ffff8881ab211d80
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 0000000000000040
RBP: ffffc90009d0fd30 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520013a1f98 R12: ffff88816b400790
R13: ffff8881ab211d80 R14: 0000000000000080 R15: 1ffff920013a1f84
FS:  0000200000004d80(0000) GS:ffff88818dc90000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff8a1c52870 CR3: 000000000e74a000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 do_exit+0x13f1/0x22c0
 do_group_exit+0x21b/0x2d0
 __x64_sys_exit_group+0x3f/0x40
 x64_sys_call+0x221a/0x2240
 do_syscall_64+0x15f/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff8a1d9cdd9
Code: Unable to access opcode bytes at 0x7ff8a1d9cdaf.
RSP: 002b:0000200000004838 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 000000000000000b RCX: 00007ff8a1d9cdd9
RDX: 00007ff8a1d9cdd9 RSI: 0000000000000000 RDI: 000000000000000b
RBP: 00007ff8a1e32d69 R08: 0000200000004d80 R09: 000000000000000b
R10: 0000200000004d80 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff8a2016038 R14: 00007ff8a2015fa0 R15: 00007fffed841718
 </TASK>
