在Python中启用seccomp后如何干净地退出？

我在项目中通过python-prctl启用了seccomp.我无法弄清楚如何彻底退出 – 结果总是杀人.

我看到一些使用ctypes或ffi来尝试引用libc的例子,但如果我期望它们使用WIFEXITED,它们似乎也有同样的问题.

示例代码如下.结果总是“我们被杀死了”.

def main():
  pid = os.fork()
  if not pid:
    prctl.set_seccomp(True)
    os.write(0, 'Hi\n')

#    os._exit(0)
#    _exit(0)
#    sys._exit(0)
#    return
#    ?!@#(*!  What do?

  endpid, status = os.waitpid(pid, 0)
  print 'Child forked as %d and returned with %d' % (endpid, status)
  if not os.WIFEXITED(status):
    print 'Exitted abnormally'
    if os.WIFSIGNALED:
      if os.WTERMSIG(status) == signal.SIGKILL:
        print 'We were killed to death'
  else:
    print 'Returned with %d' % (os.WEXITSTATUS(status))

快速更新,因为我忘记了libc的东西：

使用其中任何一个定义上面的_exit()仍会导致kill.

# FFI Method
ffi = cffi.FFI()
# Use _exit, which avoids atexit(), etc
ffi.cdef('void _exit(int);')
libc = ffi.dlopen(None)
_exit = libc._exit

…. 要么 ….

# ctypes method
libc = cdll.LoadLibrary('libc-2.18.so')
_exit = libc._exit

解决方法:

有人帮我找到了答案：

In glibc up to version 2.3, the _exit() wrapper function invoked the kernel system
call of the same name.  Since glibc 2.3, the wrapper function invokes
exit_group(2), in order to terminate all of the threads in a process.

由于_exit包含exit_group并且exit_group不在seccomp过滤器中….它会被杀死. python执行的strace显示exit_group调用.

标签：python,seccomp
来源： https://codeday.me/bug/20190624/1277426.html