uvm_fault(0xffffffff83a6b120, 0xffff800028964e71, 0, 2) -> d
kernel: page fault trap, code=2
Stopped at      memset+0x49:    repe stosb      %es:(%rdi)
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
*180323  57389      0           0  0x4000001    0  syz-executor
memset() at memset+0x49
ffs_write(ffff80002a7c4c90) at ffs_write+0xb9a sys/ufs/ffs/ffs_vnops.c:401
VOP_WRITE(fffff9006fd2e510,ffff80002a7c4d40,3,fffff90007ffd618) at VOP_WRITE+0x101 sys/kern/vfs_vops.c:245
ktrwriteraw(ffff80002a778540,fffff9006fd2e510,fffff90007ffd618,ffff80002a7c4e10,ffff80002a7c4df0) at ktrwriteraw+0x19b sys/kern/kern_ktrace.c:692
ktrsysret(ffff80002a778540,36,0,ffff80002a7c4ed0) at ktrsysret+0x17f ktrwrite2 sys/kern/kern_ktrace.c:-1 [inline]
ktrsysret(ffff80002a778540,36,0,ffff80002a7c4ed0) at ktrsysret+0x17f sys/kern/kern_ktrace.c:209
syscall(ffff80002a7c4f80) at syscall+0xad9 mi_syscall_return sys/sys/syscall_mi.h:204 [inline]
syscall(ffff80002a7c4f80) at syscall+0xad9 sys/arch/amd64/amd64/trap.c:804
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xc7812db59b0, count: 8
https://www.openbsd.org/ddb.html describes the minimum info required in bug
reports.  Insufficient info makes it difficult to find and fix bugs.
ddb> 
ddb> set $lines = 0
ddb> set $maxwidth = 0
ddb> show panic
*cpu0: uvm_fault(0xffffffff83a6b120, 0xffff800028964e71, 0, 2) -> d
ddb> show kasan
No such command
ddb> trace
memset() at memset+0x49
ffs_write(ffff80002a7c4c90) at ffs_write+0xb9a sys/ufs/ffs/ffs_vnops.c:401
VOP_WRITE(fffff9006fd2e510,ffff80002a7c4d40,3,fffff90007ffd618) at VOP_WRITE+0x101 sys/kern/vfs_vops.c:245
ktrwriteraw(ffff80002a778540,fffff9006fd2e510,fffff90007ffd618,ffff80002a7c4e10,ffff80002a7c4df0) at ktrwriteraw+0x19b sys/kern/kern_ktrace.c:692
ktrsysret(ffff80002a778540,36,0,ffff80002a7c4ed0) at ktrsysret+0x17f ktrwrite2 sys/kern/kern_ktrace.c:-1 [inline]
ktrsysret(ffff80002a778540,36,0,ffff80002a7c4ed0) at ktrsysret+0x17f sys/kern/kern_ktrace.c:209
syscall(ffff80002a7c4f80) at syscall+0xad9 mi_syscall_return sys/sys/syscall_mi.h:204 [inline]
syscall(ffff80002a7c4f80) at syscall+0xad9 sys/arch/amd64/amd64/trap.c:804
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xc7812db59b0, count: -7
ddb> show registers
rdi               0xffff800028964e71
rsi                                0
rbp               0xffff80002a7c4bb0
rbx                           0x2e71    __ALIGN_SIZE+0x1e71
rdx                              0x7
rcx                              0x7
rax                                0
r8                             0x188
r9                0xffff80002a7c4b10
r10               0x43f3df89e346237d
r11               0xffff800028964e71
r12                           0x2e71    __ALIGN_SIZE+0x1e71
r13                           0x3000    __ALIGN_SIZE+0x2000
r14               0xfffff9006fd2e510
r15                              0x1
rip               0xffffffff817ea059    memset+0x49
cs                               0x8
rflags                       0x10206    __ALIGN_SIZE+0xf206
rsp               0xffff80002a7c49a8
ss                              0x10
memset+0x49:    repe stosb      %es:(%rdi)
ddb> show proc
PROC (syz-executor) tid=180323 pid=57389 tcnt=2 stat=onproc
    flags process=0 proc=4000001<INKTR,THREAD>
    runpri=32, usrpri=50, slppri=32, nice=20
    wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
    forw=0xffffffffffffffff, list=0xffff80002a779c98,0xffffffff839c0ed8
    process=0xffff800035cdba98 user=0xffff80002a7c0000, vmspace=0xfffff9007f2382e0
    estcpu=36, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb>