Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address	= 0x30
fault code		= supervisor read data  , page not present
instruction pointer	= 0x20:0xffffffff8156d3aa
stack pointer	        = 0x28:0xfffffe002121d7a0
frame pointer	        = 0x28:0xfffffe002121d7e0
code segment		= base 0x0, limit 0xfffff, type 0x1b
			= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags	= interrupt enabled, resume, IOPL = 0
current process		= 3109 (syz-executor.0)
trap number		= 12
panic: page fault
cpuid = 1
time = 1552943071
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe002121d400
vpanic() at vpanic+0x1e0/frame 0xfffffe002121d460
panic() at panic+0x43/frame 0xfffffe002121d4c0
trap_fatal() at trap_fatal+0x4c6/frame 0xfffffe002121d540
trap_pfault() at trap_pfault+0x9f/frame 0xfffffe002121d5b0
trap() at trap+0x44d/frame 0xfffffe002121d6d0
calltrap() at calltrap+0x8/frame 0xfffffe002121d6d0
--- trap 0xc, rip = 0xffffffff8156d3aa, rsp = 0xfffffe002121d7a0, rbp = 0xfffffe002121d7e0 ---
vm_page_unhold_pages() at vm_page_unhold_pages+0x5a/frame 0xfffffe002121d7e0
pipe_write() at pipe_write+0x16d8/frame 0xfffffe002121d8b0
dofilewrite() at dofilewrite+0xfd/frame 0xfffffe002121d910
kern_writev() at kern_writev+0x66/frame 0xfffffe002121d950
sys_writev() at sys_writev+0x50/frame 0xfffffe002121d980
amd64_syscall() at amd64_syscall+0x436/frame 0xfffffe002121dab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe002121dab0
--- syscall (198, FreeBSD ELF64, nosys), rip = 0x412e5a, rsp = 0x7fffdfffdf38, rbp = 0x3 ---
KDB: enter: panic
[ thread pid 3109 tid 100568 ]
Stopped at      kdb_enter+0x6a: movq    $0,kdb_why