VBoxLinuxAddiiotns not install successfully

[yasu]

The display resolution doesn't match the Windows7 hostOS.
So I tried to execute VBoxLinuxAdditions.run in RHEL7.2 Guest OS, the following message appeared.
modprobe vboxsf failed.
And resolution was not improved after reboot.
Does anyone know how to do improve resolution under RHEL7.2 GuestOS?

[yasu]

Vbox revision is 5.2.18.

[yasu]

I rebooted not only guest OS but also host OS. I found this issue has gone away.
Thank you.