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

netfilter: nftables: release flowtable after rcu grace period on error

Call synchronizercu() after unregistering the hooks from error path, since a hook that already refers to this flowtable can be already registered, exposing this flowtable to packet path and nfnetlinkhook control plane.

This error path is rare, it should only happen by reaching the maximum number hooks or by failing to set up to hardware offload, just call synchronizercu().

There is a check for already used device hooks by different flowtable that could result in EEXIST at this late stage. The hook parser can be updated to perform this check earlier to this error path really becomes rarely exercised.

Uncovered by KASAN reported as use-after-free from nfnetlinkhook path when dumping hooks.