syzbot

panic: Bad entry start/end for new stack entry
cpuid = 0
time = 1561515515
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe0016ae3370
vpanic() at vpanic+0x1e0/frame 0xfffffe0016ae33d0
panic() at panic+0x43/frame 0xfffffe0016ae3430
vm_map_stack_locked() at vm_map_stack_locked+0x364/frame 0xfffffe0016ae34a0
vm_map_stack() at vm_map_stack+0x11f/frame 0xfffffe0016ae3500
exec_new_vmspace() at exec_new_vmspace+0x4bd/frame 0xfffffe0016ae3570
exec_elf64_imgact() at exec_elf64_imgact+0x1262/frame 0xfffffe0016ae3670
kern_execve() at kern_execve+0x7d8/frame 0xfffffe0016ae39c0
start_init() at start_init+0x249/frame 0xfffffe0016ae3a60
fork_exit() at fork_exit+0xb0/frame 0xfffffe0016ae3ab0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe0016ae3ab0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
KDB: enter: panic
[ thread pid 1 tid 100002 ]
Stopped at      kdb_enter+0x6a: movq    $0,kdb_why
db>