Merge "even more O_CLOEXECs!" am: bb5b6454 am: 6130adad

// Utility to close down the Zygote socket file descriptors while

// the child is still running as root with Zygote's privileges.  Each

// descriptor (if any) is closed via dup2(), replacing it with a valid

// descriptor (if any) is closed via dup3(), replacing it with a valid

// (open) descriptor to /dev/null.

static void DetachDescriptors(JNIEnv* env,

                              fail_fn_t fail_fn) {

  if (fds_to_close.size() > 0) {

    android::base::unique_fd devnull_fd(open("/dev/null", O_RDWR));

    android::base::unique_fd devnull_fd(open("/dev/null", O_RDWR | O_CLOEXEC));

    if (devnull_fd == -1) {

      fail_fn(std::string("Failed to open /dev/null: ").append(strerror(errno)));

    }

    for (int fd : fds_to_close) {

      ALOGV("Switching descriptor %d to /dev/null", fd);

      if (dup2(devnull_fd, fd) == -1) {

        fail_fn(StringPrintf("Failed dup2() on descriptor %d: %s", fd, strerror(errno)));

      if (dup3(devnull_fd, fd, O_CLOEXEC) == -1) {

        fail_fn(StringPrintf("Failed dup3() on descriptor %d: %s", fd, strerror(errno)));

      }

    }

  }