netbsd boot error: panic: UBSan: Undefined Behavior in /syzkaller/managers/netbsd-kubsan/kernel/sys/kern/init_main.c:LINE, left shift of AD

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: add389a7 Use fork() rather than vfork() when forking to ru..
git tree: netbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=172d1e71e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=824b23e1f4b6c76b
dashboard link: https://syzkaller.appspot.com/bug?extid=f02ca5f83ac7196b8afd
compiler: g++ (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f02ca5...@syzkaller.appspotmail.com

[ 1.0000000] panic: UBSan: Undefined Behavior in
/syzkaller/managers/netbsd-kubsan/kernel/sys/kern/init_main.c:1177:35, left
shift of 1888145 by 12 places cannot be represented in type 'int'

[ 1.0000000] cpu0: Begin traceback...
[ 1.0000000] vpanic() at netbsd:vpanic+0x2aa sys/kern/subr_prf.c:336
[ 1.0000000] isAlreadyReported() at netbsd:isAlreadyReported
[ 1.0000000] HandleShiftOutOfBounds() at
netbsd:HandleShiftOutOfBounds+0x28b sys/../common/lib/libc/misc/ubsan.c:470
[ 1.0000000] banner() at netbsd:banner+0x117 sys/kern/init_main.c:1177
[ 1.0000000] cpu_startup() at netbsd:cpu_startup+0x2d6
sys/arch/amd64/amd64/machdep.c:410
[ 1.0000000] main() at netbsd:main+0x16a sys/kern/init_main.c:339
[ 1.0000000] cpu0: End traceback...
[ 1.0000000] fatal breakpoint trap in supervisor mode
[ 1.0000000] trap type 1 code 0 rip 0xffffffff8021dd9d cs 0x8 rflags
0x202 cr2 0 ilevel 0x8 rsp 0xffffffff8625d710
[ 1.0000000] curlwp 0xffffffff85344aa0 pid 0.1 lowest kstack
0xffffffff862592c0
Stopped in pid 0.1 (system) at netbsd:breakpoint+0x5: leave
db{0}>


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.