------------[ cut here ]------------
!valid_signal(sig)
WARNING: kernel/signal.c:2174 at do_notify_parent+0xd0e/0xe20, CPU#0: syz.8.1977/13832
Modules linked in:
CPU: 0 UID: 0 PID: 13832 Comm: syz.8.1977 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+0xd0e/0xe20
Code: c6 05 72 51 8f 0e 01 48 c7 c7 e0 3a cb 8b be a3 08 00 00 48 c7 c2 60 3c cb 8b e8 cd 7b 17 00 e9 2d fa ff ff e8 23 30 3b 00 90 <0f> 0b 90 45 31 e4 e9 1c ff ff ff e8 12 30 3b 00 90 0f 0b 90 e9 e5
RSP: 0018:ffffc9000393fc20 EFLAGS: 00010093
RAX: ffffffff818a10ad RBX: dffffc0000000000 RCX: ffff88816943d940
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 0000000000000040
RBP: ffffc9000393fd90 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000727fa4 R12: ffff888177702d10
R13: ffff88816943d940 R14: 0000000000000080 R15: 1ffff92000727f90
FS:  00007fc8207176c0(0000) GS:ffff88818dcb8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc81f757f70 CR3: 0000000101770000 CR4: 00000000000006f0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 do_exit+0x13f8/0x2360
 __x64_sys_exit+0x40/0x40
 x64_sys_call+0x2231/0x2240
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc81f79ce59
Code: Unable to access opcode bytes at 0x7fc81f79ce2f.
RSP: 002b:00007fc820716fd8 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 00007fc81fa15fa0 RCX: 00007fc81f79ce59
RDX: 00007fc8207179c8 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fc81f832e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc81fa16038 R14: 00007fc81fa15fa0 R15: 00007fffa62a3df8
 </TASK>
