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

[ Upstream commit d73f4b53aaaea4c95f245e491aa5eeb8a21874ce ]

Call synchronize_rcu() 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 nfnetlink_hook
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
synchronize_rcu().

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 nfnetlink_hook path
when dumping hooks.

BUG=b/500321842
TEST=presubmit
RELEASE_NOTE=Fixed KCTF-7e3955b in the Linux kernel.

Fixes: 3b49e2e94e6e ("netfilter: nf_tables: add flow table netlink frontend")
Reported-by: Yiming Qian <yimingqian591@gmail.com>
Change-Id: Ie828d439c7a56b916c762820ac98e9d1685af437
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/144543
Reviewed-by: Kevin Berry <kpberry@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>