Commit 6a33d8b7 authored by Pablo Neira Ayuso's avatar Pablo Neira Ayuso Committed by Florian Westphal
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netfilter: nf_tables: fix GC transaction races with netns and netlink event exit path 



Netlink event path is missing a synchronization point with GC
transactions. Add GC sequence number update to netns release path and
netlink event path, any GC transaction losing race will be discarded.

Fixes: 5f68718b ("netfilter: nf_tables: GC transaction API to avoid race with control plane")
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
parent 5310760a

net/netfilter/nf_tables_api.c

+32 −4
Original line number Diff line number Diff line
@@ -9739,6 +9739,22 @@ static void nft_set_commit_update(struct list_head *set_update_list) 
	}

}



static unsigned int nft_gc_seq_begin(struct nftables_pernet *nft_net)

{

	unsigned int gc_seq;



	/* Bump gc counter, it becomes odd, this is the busy mark. */

	gc_seq = READ_ONCE(nft_net->gc_seq);

	WRITE_ONCE(nft_net->gc_seq, ++gc_seq);



	return gc_seq;

}



static void nft_gc_seq_end(struct nftables_pernet *nft_net, unsigned int gc_seq)

{

	WRITE_ONCE(nft_net->gc_seq, ++gc_seq);

}



static int nf_tables_commit(struct net *net, struct sk_buff *skb)

{

	struct nftables_pernet *nft_net = nft_pernet(net);
@@ -9824,9 +9840,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb) 


	WRITE_ONCE(nft_net->base_seq, base_seq);



	/* Bump gc counter, it becomes odd, this is the busy mark. */

	gc_seq = READ_ONCE(nft_net->gc_seq);

	WRITE_ONCE(nft_net->gc_seq, ++gc_seq);

	gc_seq = nft_gc_seq_begin(nft_net);



	/* step 3. Start new generation, rules_gen_X now in use. */

	net->nft.gencursor = nft_gencursor_next(net);
@@ -10039,7 +10053,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb) 
	nf_tables_gen_notify(net, skb, NFT_MSG_NEWGEN);

	nf_tables_commit_audit_log(&adl, nft_net->base_seq);



	WRITE_ONCE(nft_net->gc_seq, ++gc_seq);

	nft_gc_seq_end(nft_net, gc_seq);

	nf_tables_commit_release(net);



	return 0;
@@ -11040,6 +11054,7 @@ static int nft_rcv_nl_event(struct notifier_block *this, unsigned long event, 
	struct net *net = n->net;

	unsigned int deleted;

	bool restart = false;

	unsigned int gc_seq;



	if (event != NETLINK_URELEASE || n->protocol != NETLINK_NETFILTER)

		return NOTIFY_DONE;
@@ -11047,6 +11062,9 @@ static int nft_rcv_nl_event(struct notifier_block *this, unsigned long event, 
	nft_net = nft_pernet(net);

	deleted = 0;

	mutex_lock(&nft_net->commit_mutex);



	gc_seq = nft_gc_seq_begin(nft_net);



	if (!list_empty(&nf_tables_destroy_list))

		rcu_barrier();

again:
@@ -11069,6 +11087,8 @@ static int nft_rcv_nl_event(struct notifier_block *this, unsigned long event, 
		if (restart)

			goto again;

	}

	nft_gc_seq_end(nft_net, gc_seq);



	mutex_unlock(&nft_net->commit_mutex);



	return NOTIFY_DONE;
@@ -11106,12 +11126,20 @@ static void __net_exit nf_tables_pre_exit_net(struct net *net) 
static void __net_exit nf_tables_exit_net(struct net *net)

{

	struct nftables_pernet *nft_net = nft_pernet(net);

	unsigned int gc_seq;



	mutex_lock(&nft_net->commit_mutex);



	gc_seq = nft_gc_seq_begin(nft_net);



	if (!list_empty(&nft_net->commit_list) ||

	    !list_empty(&nft_net->module_list))

		__nf_tables_abort(net, NFNL_ABORT_NONE);



	__nft_release_tables(net);



	nft_gc_seq_end(nft_net, gc_seq);



	mutex_unlock(&nft_net->commit_mutex);

	WARN_ON_ONCE(!list_empty(&nft_net->tables));

	WARN_ON_ONCE(!list_empty(&nft_net->module_list));