Merge branch 'net-ipv4-fix-circular-list-infinite-loop'

Florian Westphal says:

====================
net: ipv4: fix circular-list infinite loop

Tariq and Ran reported a regression caused by net-next commit
2638eb8b

 ("net: ipv4: provide __rcu annotation for ifa_list").

This happens when net.ipv4.conf.$dev.promote_secondaries sysctl is
enabled -- we can arrange for ifa->next to point at ifa, so next
process that tries to walk the list loops forever.

Fix this and extend rtnetlink.sh with a small test case for this.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>