syzbot

uvm_fault(fffffd806eabc3e0,95821d65000,0,2) at uvm_fault+0x106 sys/uvm/uvm_fault.c:627
upageflttrap(ffff80003c405d80,95821d65c18) at upageflttrap+0xa9 sys/arch/amd64/amd64/trap.c:192
usertrap(ffff80003c405d80) at usertrap+0x42f sys/arch/amd64/amd64/trap.c:632
recall_trap() at recall_trap+0x8
end trace frame: 0x0, count: -14
ddb{0}> machine ddbcpu 1
Stopped at      done_flush+0x38:        movl    %eax,%dr6
ddb{1}> trace
end trace frame: 0x0, count: -1