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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>,
	Daniel Bristot de Oliveira <bristot@kernel.org>,
	Boqun Feng <boqun.feng@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Eric Dumazet <edumazet@google.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Waiman Long <longman@redhat.com>,
	Will Deacon <will@kernel.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Florian Westphal <fw@strlen.de>,
	Jozsef Kadlecsik <kadlec@netfilter.org>,
	Nikolay Aleksandrov <razor@blackwall.org>,
	Pablo Neira Ayuso <pablo@netfilter.org>,
	Roopa Prabhu <roopa@nvidia.com>,
	bridge@lists.linux.dev,
	coreteam@netfilter.org,
	netfilter-devel@vger.kernel.org
Subject: [PATCH v6 net-next 07/15] netfilter: br_netfilter: Use nested-BH locking for brnf_frag_data_storage.
Date: Wed, 12 Jun 2024 18:44:33 +0200
Message-ID: <20240612170303.3896084-8-bigeasy@linutronix.de>
In-Reply-To: <20240612170303.3896084-1-bigeasy@linutronix.de>
References: <20240612170303.3896084-1-bigeasy@linutronix.de>
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brnf_frag_data_storage is a per-CPU variable and relies on disabled BH
for its locking. Without per-CPU locking in local_bh_disable() on
PREEMPT_RT this data structure requires explicit locking.

Add a local_lock_t to the data structure and use local_lock_nested_bh()
for locking. This change adds only lockdep coverage and does not alter
the functional behaviour for !PREEMPT_RT.

Cc: Florian Westphal <fw@strlen.de>
Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
Cc: Nikolay Aleksandrov <razor@blackwall.org>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Roopa Prabhu <roopa@nvidia.com>
Cc: bridge@lists.linux.dev
Cc: coreteam@netfilter.org
Cc: netfilter-devel@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 net/bridge/br_netfilter_hooks.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hook=
s.c
index bf30c50b56895..3c9f6538990ea 100644
--- a/net/bridge/br_netfilter_hooks.c
+++ b/net/bridge/br_netfilter_hooks.c
@@ -137,6 +137,7 @@ static inline bool is_pppoe_ipv6(const struct sk_buff *=
skb,
 #define NF_BRIDGE_MAX_MAC_HEADER_LENGTH (PPPOE_SES_HLEN + ETH_HLEN)
=20
 struct brnf_frag_data {
+	local_lock_t bh_lock;
 	char mac[NF_BRIDGE_MAX_MAC_HEADER_LENGTH];
 	u8 encap_size;
 	u8 size;
@@ -144,7 +145,9 @@ struct brnf_frag_data {
 	__be16 vlan_proto;
 };
=20
-static DEFINE_PER_CPU(struct brnf_frag_data, brnf_frag_data_storage);
+static DEFINE_PER_CPU(struct brnf_frag_data, brnf_frag_data_storage) =3D {
+	.bh_lock =3D INIT_LOCAL_LOCK(bh_lock),
+};
=20
 static void nf_bridge_info_free(struct sk_buff *skb)
 {
@@ -850,6 +853,7 @@ static int br_nf_dev_queue_xmit(struct net *net, struct=
 sock *sk, struct sk_buff
 {
 	struct nf_bridge_info *nf_bridge =3D nf_bridge_info_get(skb);
 	unsigned int mtu, mtu_reserved;
+	int ret;
=20
 	mtu_reserved =3D nf_bridge_mtu_reduction(skb);
 	mtu =3D skb->dev->mtu;
@@ -882,6 +886,7 @@ static int br_nf_dev_queue_xmit(struct net *net, struct=
 sock *sk, struct sk_buff
=20
 		IPCB(skb)->frag_max_size =3D nf_bridge->frag_max_size;
=20
+		local_lock_nested_bh(&brnf_frag_data_storage.bh_lock);
 		data =3D this_cpu_ptr(&brnf_frag_data_storage);
=20
 		if (skb_vlan_tag_present(skb)) {
@@ -897,7 +902,9 @@ static int br_nf_dev_queue_xmit(struct net *net, struct=
 sock *sk, struct sk_buff
 		skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
 						 data->size);
=20
-		return br_nf_ip_fragment(net, sk, skb, br_nf_push_frag_xmit);
+		ret =3D br_nf_ip_fragment(net, sk, skb, br_nf_push_frag_xmit);
+		local_unlock_nested_bh(&brnf_frag_data_storage.bh_lock);
+		return ret;
 	}
 	if (IS_ENABLED(CONFIG_NF_DEFRAG_IPV6) &&
 	    skb->protocol =3D=3D htons(ETH_P_IPV6)) {
@@ -909,6 +916,7 @@ static int br_nf_dev_queue_xmit(struct net *net, struct=
 sock *sk, struct sk_buff
=20
 		IP6CB(skb)->frag_max_size =3D nf_bridge->frag_max_size;
=20
+		local_lock_nested_bh(&brnf_frag_data_storage.bh_lock);
 		data =3D this_cpu_ptr(&brnf_frag_data_storage);
 		data->encap_size =3D nf_bridge_encap_header_len(skb);
 		data->size =3D ETH_HLEN + data->encap_size;
@@ -916,8 +924,12 @@ static int br_nf_dev_queue_xmit(struct net *net, struc=
t sock *sk, struct sk_buff
 		skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
 						 data->size);
=20
-		if (v6ops)
-			return v6ops->fragment(net, sk, skb, br_nf_push_frag_xmit);
+		if (v6ops) {
+			ret =3D v6ops->fragment(net, sk, skb, br_nf_push_frag_xmit);
+			local_unlock_nested_bh(&brnf_frag_data_storage.bh_lock);
+			return ret;
+		}
+		local_unlock_nested_bh(&brnf_frag_data_storage.bh_lock);
=20
 		kfree_skb(skb);
 		return -EMSGSIZE;
--=20
2.45.1