uvm_fault(0xffffffff839859e8, 0xffff80001fff2038, 0, 1) -> d
kernel: page fault trap, code=0
Stopped at      ffs2_balloc+0xa0a:      movq    0(%rcx,%rax,8),%r14
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
*239254  79675      0           0  0x4000000    0  syz-executor
ffs2_balloc(fffffd806fd42100,840002ffff,1,fffffd8007ffd548,3,ffff80002a787a88) at ffs2_balloc+0xa0a sys/ufs/ffs/ffs_balloc.c:614
ffs_write(ffff80002a787b10) at ffs_write+0x4f9 sys/ufs/ffs/ffs_vnops.c:345
VOP_WRITE(fffffd806c3a30e0,ffff80002a787cc8,17,fffffd8007ffd548) at VOP_WRITE+0x101 sys/kern/vfs_vops.c:245
vn_write(fffffd8079c70e18,ffff80002a787cc8,0) at vn_write+0x1c2 sys/kern/vfs_vnops.c:414
dofilewritev(ffff80002f0c1240,5,ffff80002a787cc8,0,ffff80002a787d70) at dofilewritev+0x2bd sys/kern/sys_generic.c:384
sys_write(ffff80002f0c1240,ffff80002a787e20,ffff80002a787d70) at sys_write+0xa2 sys/kern/sys_generic.c:300
syscall(ffff80002a787e20) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002a787e20) at syscall+0x962 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x692641a61e0, count: 7
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(0xffffffff839859e8, 0xffff80001fff2038, 0, 1) -> d
ddb> trace
ffs2_balloc(fffffd806fd42100,840002ffff,1,fffffd8007ffd548,3,ffff80002a787a88) at ffs2_balloc+0xa0a sys/ufs/ffs/ffs_balloc.c:614
ffs_write(ffff80002a787b10) at ffs_write+0x4f9 sys/ufs/ffs/ffs_vnops.c:345
VOP_WRITE(fffffd806c3a30e0,ffff80002a787cc8,17,fffffd8007ffd548) at VOP_WRITE+0x101 sys/kern/vfs_vops.c:245
vn_write(fffffd8079c70e18,ffff80002a787cc8,0) at vn_write+0x1c2 sys/kern/vfs_vnops.c:414
dofilewritev(ffff80002f0c1240,5,ffff80002a787cc8,0,ffff80002a787d70) at dofilewritev+0x2bd sys/kern/sys_generic.c:384
sys_write(ffff80002f0c1240,ffff80002a787e20,ffff80002a787d70) at sys_write+0xa2 sys/kern/sys_generic.c:300
syscall(ffff80002a787e20) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff80002a787e20) at syscall+0x962 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x692641a61e0, count: -8
ddb> show registers
rdi                                0
rsi                              0x2
rbp               0xffff80002a787a30
rbx               0xfffffd806fd42100
rdx               0xffff8000015abe00
rcx               0xffff80001fff2000
rax                              0x7
r8                0xffffffffffffffff
r9                0xffff80002a787a88
r10                                0
r11               0x999ef8f51cddce82
r12                              0x1
r13               0xffff800000c47800
r14               0xffff80002a7878d0
r15               0xfffffd80709a0578
rip               0xffffffff8319cc2a    ffs2_balloc+0xa0a
cs                               0x8
rflags                       0x10246    __ALIGN_SIZE+0xf246
rsp               0xffff80002a7878c0
ss                              0x10
ffs2_balloc+0xa0a:      movq    0(%rcx,%rax,8),%r14
ddb> show proc
PROC (syz-executor) tid=239254 pid=79675 tcnt=2 stat=onproc
    flags process=0 proc=4000000<THREAD>
    runpri=32, usrpri=50, slppri=32, nice=20
    wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
    forw=0xffffffffffffffff, list=0xffff80002f0c0a78,0xffff80003c90aa98
    process=0xffff80002a760920 user=0xffff80002a782000, vmspace=0xfffffd806cb292f0
    estcpu=1, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb>