netfilter: nf_tables: mark newset as dead on transaction abort

If a transaction is aborted, we should mark the to-be-released NEWSET dead,
just like commit path does for DEL and DESTROYSET commands.

In both cases all remaining elements will be released via
set->ops->destroy().

The existing abort code does NOT post the actual release to the work queue.
Also the entire __nf_tables_abort() function is wrapped in gc_seq
begin/end pair.

Therefore, async gc worker will never try to release the pending set
elements, as gc sequence is always stale.

It might be possible to speed up transaction aborts via work queue too,
this would result in a race and a possible use-after-free.

So fix this before it becomes an issue.

Fixes: 5f68718 ("netfilter: nf_tables: GC transaction API to avoid race with control plane")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -10464,6 +10464,7 @@ static int __nf_tables_abort(struct net *net, enum nfnl_abort_action action)
  nft_trans_destroy(trans);
  break;
  }
+ nft_trans_set(trans)->dead = 1;
  list_del_rcu(&nft_trans_set(trans)->list);
  break;
  case NFT_MSG_DELSET: