GPF due to NULL pointer dereference in rt6_ifdown was reported allowing local attacker to cause system denia-of-service. Bug report (reproducer included): https://marc.info/?l=linux-kernel&m=149806759923073&w=2
Created kernel tracking bugs for this issue: Affects: fedora-all [bug 1492641]
this is not a security flaw, so closing this bz as not-a-security-bug. fixing this as a regular bugfix is handled in bz1491465.
This was fixed for Fedora with the 4.13 rebases.