In the Linux kernel, the following vulnerability has been resolved:

netfilter: flowtable: hold reference on ct until flow is released

nf ct put() releases the ct->ext area inmediately, the rcu typesafe semantics also allow to refer to the wrong conntrack from the flowtable datapath. Hold reference on ct until flow is released after rcu grace period.

Add rcu barrier() on module exit path, to ensure pending flow entries are release before module goes away.