[PATCH -stable,5.15 07/17] netfilter: nf_tables: fix GC transaction races with netns and netlink event exit path

[Pablo Neira Ayuso <pablo@netfilter.org>]

commit 6a33d8b73dfac0a41f3877894b38082bd0c9a5bc upstream.

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: 5f68718b34a5 ("netfilter: nf_tables: GC transaction API to avoid race with control plane")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 36 +++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 194b78900bd3..aadcb2a5dc81 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -9207,6 +9207,22 @@ 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);
@@ -9292,9 +9308,7 @@ 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);
@@ -9485,7 +9499,7 @@ 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;
@@ -10468,6 +10482,7 @@ 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;
@@ -10475,6 +10490,9 @@ 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))
 		nf_tables_trans_destroy_flush_work();
 again:
@@ -10497,6 +10515,8 @@ 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;
@@ -10535,12 +10555,20 @@ 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));
-- 
2.30.2