panic: fdrop: invalid f_count -1
cpuid = 0
Trace beginning at frame 0xfffff80118c43768
fdrop() at fdrop+0x10e 0xffffffff806314de 
fdrop() at fdrop+0x10e 0xffffffff806314de 
closef() at closef+0x32 0xffffffff80631f22 
fdfree() at fdfree+0x15e 0xffffffff8063351e 
exit1() at exit1+0x13f 0xffffffff8063f85f 
sys_exit() at sys_exit+0xe 0xffffffff8063fdfe 
Debugger("panic")

CPU0 stopping CPUs: 0x0000003e
 stopped
Stopped at      Debugger+0x7c:  movb    $0,0xbdaf09(%rip)
db>