syzbot

uvm_fault(fffffd806bec4018,19baf543000,0,1) at uvm_fault+0x159 sys/uvm/uvm_fault.c:673
upageflttrap(ffff80003c547af0,19baf543128) at upageflttrap+0xa9 sys/arch/amd64/amd64/trap.c:188
usertrap(ffff80003c547af0) at usertrap+0x2d8 sys/arch/amd64/amd64/trap.c:436
recall_trap() at recall_trap+0x8
end of kernel
end trace frame: 0x7e8a0466b860, count: -12
ddb{0}> machine ddbcpu 1
Stopped at      db_enter+0x25:  addq    $0x8,%rsp
ddb{1}> trace
db_enter() at db_enter+0x25 sys/arch/amd64/amd64/db_interface.c:438
witness_checkorder(fffffd8073728cb8,9,0) at witness_checkorder+0x1047
rw_do_enter_write(fffffd8073728ca0,1) at rw_do_enter_write+0xb7 sys/kern/kern_rwlock.c:233
rrw_enter(fffffd8073728ca0,1) at rrw_enter+0xc6 sys/kern/kern_rwlock.c:616
VOP_LOCK(fffffd807852a870,2001) at VOP_LOCK+0xa6 sys/kern/vfs_vops.c:524
vn_lock(fffffd807852a870,2001) at vn_lock+0xa4 sys/kern/vfs_vnops.c:570
vfs_getcwd_common(fffffd807852a870,fffffd807852a360,0,0,200,0,361a1be5df84eca4) at vfs_getcwd_common+0xd1 sys/kern/vfs_getcwd.c:287
vn_isunder(fffffd807852a870,fffffd807852a360,ffff8000ffff6020) at vn_isunder+0x56 sys/kern/vfs_vnops.c:694
unp_externalize(fffffd80675f0400,33,0) at unp_externalize+0x286 sys/kern/uipc_usrreq.c:1086
soreceive(ffff800010fd52e0,ffff80003c513c48,ffff80003c513bf8,0,ffff80003c513c38,ffff80003c513dbc,86bf4f76ca0638cc) at soreceive+0xc73 sys/kern/uipc_socket.c:1021
recvit(ffff8000ffff6020,4,ffff80003c513d90,0,ffff80003c513e40) at recvit+0x40a sys/kern/uipc_syscalls.c:1072
sys_recvmsg(ffff8000ffff6020,ffff80003c513ef0,ffff80003c513e40) at sys_recvmsg+0x1bf sys/kern/uipc_syscalls.c:872
syscall(ffff80003c513ef0) at syscall+0xbc6 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003c513ef0) at syscall+0xbc6 sys/arch/amd64/amd64/trap.c:577
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xe41993812f0, count: -14