Commit 767d1216 authored by Pablo Neira Ayuso's avatar Pablo Neira Ayuso
Browse files

netfilter: nftables: fix possible UAF over chains from packet path in netns 



Although hooks are released via call_rcu(), chain and rule objects are
immediately released while packets are still walking over these bits.

This patch adds the .pre_exit callback which is invoked before
synchronize_rcu() in the netns framework to stay safe.

Remove a comment which is not valid anymore since the core does not use
synchronize_net() anymore since 8c873e21 ("netfilter: core: free
hooks with call_rcu").

Suggested-by: default avatarFlorian Westphal <fw@strlen.de>
Fixes: df05ef87 ("netfilter: nf_tables: release objects on netns destruction")
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent a3005b0f

net/netfilter/nf_tables_api.c

+19 −6
Original line number Diff line number Diff line
@@ -8949,6 +8949,17 @@ int __nft_release_basechain(struct nft_ctx *ctx) 
}

EXPORT_SYMBOL_GPL(__nft_release_basechain);



static void __nft_release_hooks(struct net *net)

{

	struct nft_table *table;

	struct nft_chain *chain;



	list_for_each_entry(table, &net->nft.tables, list) {

		list_for_each_entry(chain, &table->chains, list)

			nf_tables_unregister_hook(net, table, chain);

	}

}



static void __nft_release_tables(struct net *net)

{

	struct nft_flowtable *flowtable, *nf;
@@ -8964,10 +8975,6 @@ static void __nft_release_tables(struct net *net) 


	list_for_each_entry_safe(table, nt, &net->nft.tables, list) {

		ctx.family = table->family;



		list_for_each_entry(chain, &table->chains, list)

			nf_tables_unregister_hook(net, table, chain);

		/* No packets are walking on these chains anymore. */

		ctx.table = table;

		list_for_each_entry(chain, &table->chains, list) {

			ctx.chain = chain;
@@ -9016,6 +9023,11 @@ static int __net_init nf_tables_init_net(struct net *net) 
	return 0;

}



static void __net_exit nf_tables_pre_exit_net(struct net *net)

{

	__nft_release_hooks(net);

}



static void __net_exit nf_tables_exit_net(struct net *net)

{

	mutex_lock(&net->nft.commit_mutex);
@@ -9030,6 +9042,7 @@ static void __net_exit nf_tables_exit_net(struct net *net) 


static struct pernet_operations nf_tables_net_ops = {

	.init		= nf_tables_init_net,

	.pre_exit	= nf_tables_pre_exit_net,

	.exit		= nf_tables_exit_net,

};