[ 199.5218867] panic: kernel diagnostic assertion "vp->v_usecount != 0" failed: file "/syzkaller/managers/netbsd/kernel/sys/kern/vfs_vnode.c", line 869 
[ 199.5420204] cpu0: Begin traceback...
[ 199.5461670] vpanic() at netbsd:vpanic+0x214
[ 199.5552740] _GLOBAL__sub_D_65535_0_cpu_configure() at netbsd:_GLOBAL__sub_D_65535_0_cpu_configure
[ 199.5700647] vref() at netbsd:vref+0x54
[ 199.5775290] getcwd_common() at netbsd:getcwd_common+0x118
[ 199.5886571] vn_isunder() at netbsd:vn_isunder+0x1e
[ 199.6000412] lookup_once() at netbsd:lookup_once+0x23f
[ 199.6220425] namei_tryemulroot() at netbsd:namei_tryemulroot+0xba6
[ 199.6331712] namei() at netbsd:namei+0x67
[ 199.6443005] chdir_lookup() at netbsd:chdir_lookup+0x161
[ 199.6554298] sys_chroot() at netbsd:sys_chroot+0xdb
[ 199.6665560] sys___syscall() at netbsd:sys___syscall+0xe2
[ 199.6776857] syscall() at netbsd:syscall+0x32e
[ 199.6776857] --- syscall (number 198) ---
[ 199.6929473] 7eb05b03f4aa:
[ 199.6929473] cpu0: End traceback...

[ 199.7018035] dumping to dev 4,1 (offset=0, size=0): not possible
[ 199.7018035] rebooting...
SeaBIOS (version 1.8.2-20190122_225043-google)
Total RAM Size = 0x00000001e0000000 = 7680 MiB
CPUs found: 2     Max CPUs supported: 2
found virtio-scsi at 0:3
virtio-scsi vendor='Google' product='PersistentDisk' rev='1' type=0 removable=0
virtio-scsi blksize=512 sectors=4194304 = 2048 MiB
drive 0x000f29c0: PCHS=0/0/0 translation=lba LCHS=520/128/63 s=4194304
Booting from Hard Disk 0...

>> NetBSD/x86 BIOS Boot, Revision 5.10 (Tue Jul 17 14:59:51 UTC 2018) (from NetBSD 8.0)
>> Memory: 639/3144640 k

     1. Boot normally
     2. Boot single user
     3. Disable ACPI
     4. Disable ACPI and SMP
     5. Drop to boot prompt