------------[ cut here ]------------
!valid_signal(sig)
WARNING: kernel/signal.c:2174 at do_notify_parent+0xea8/0x10b0 kernel/signal.c:2174, CPU#3: syz.0.17/5928
Modules linked in:
CPU: 3 UID: 0 PID: 5928 Comm: syz.0.17 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: 0018:ffffc90004647ce8 EFLAGS: 00010093
RAX: 0000000000000000 RBX: ffff88802b1fa500 RCX: ffffffff81ca9f1b
RDX: ffff88802b1fa500 RSI: ffffffff81caad07 RDI: ffff88802b1fa500
RBP: 0000000000000080 R08: 0000000000000007 R09: 0000000000000040
R10: 0000000000000080 R11: 0000000000000000 R12: 1ffff920008c8fa0
R13: dffffc0000000000 R14: 0000000000000080 R15: ffff888032528000
FS:  0000000000000000(0000) GS:ffff8880d6679000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbccf6dbff8 CR3: 000000000e596000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 exit_notify kernel/exit.c:757 [inline]
 do_exit+0x1b05/0x2a60 kernel/exit.c:987
 __do_sys_exit kernel/exit.c:1084 [inline]
 __se_sys_exit kernel/exit.c:1082 [inline]
 __x64_sys_exit+0x42/0x50 kernel/exit.c:1082
 x64_sys_call+0x152e/0x1530 arch/x86/include/generated/asm/syscalls_64.h:61
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbcce79cdd9
Code: Unable to access opcode bytes at 0x7fbcce79cdaf.
RSP: 002b:00007fbccf6fcfd8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 00007fbccea15fa0 RCX: 00007fbcce79cdd9
RDX: 00007fbccf6fd9c8 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fbcce832d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbccea16038 R14: 00007fbccea15fa0 R15: 00007ffef0acc708
 </TASK>