[ 148.4306115] panic: kernel diagnostic assertion "!ff->ff_exclose" failed: file "/syzkaller/managers/netbsd/kernel/sys/kern/kern_descrip.c", line 1571 
[ 148.4557256] cpu0: Begin traceback...
[ 148.4557256] vpanic() at netbsd:vpanic+0x214
[ 148.4642990] _GLOBAL__sub_D_65535_0_cpu_configure() at netbsd:_GLOBAL__sub_D_65535_0_cpu_configure
[ 148.4856983] fd_free() at netbsd:fd_free+0x2f6
[ 148.4967091] exit1() at netbsd:exit1+0x265
[ 148.5077253] sys_exit() at netbsd:sys_exit+0x6c
[ 148.5187414] syscall() at netbsd:syscall+0x32e
[ 148.5187414] --- syscall (number 1) ---
[ 148.5333149] 7b53672fe47a:
[ 148.5333149] cpu0: End traceback...

[ 148.5422083] dumping to dev 4,1 (offset=0, size=0): not possible
[ 148.5422083] rebooting...
SeaBIOS (version 1.8.2-20190322_093631-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