From: Guillaume Nault <g.na...@alphalink.fr> Date: Mon, 14 Mar 2016 18:59:40 +0100
> Testing ->private_data without lock in ppp_ioctl() before calling > ppp_unattached_ioctl() is fine, because either ->private_data is > not NULL and thus is stable, or it is and ppp_unattached_ioctl() > takes care of not overriding ->private_data, should its value get > modified before taking the mutex. This is exactly the ambiguous behavior I want you to avoid. The decision should be atomic from ppp_ioctl()'s test all the way until ppp_unattached_ioctl() does it's work.
