netdev - [PATCH net 4/8] arp: use RCU protection in arp

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Message-ID: <20250207135841.1948589-5-edumazet@google.com>
Date: Fri,  7 Feb 2025 13:58:36 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, David Ahern <dsahern@...nel.org>, 
	Kuniyuki Iwashima <kuniyu@...zon.com>, Simon Horman <horms@...nel.org>, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net 4/8] arp: use RCU protection in arp_xmit()

arp_xmit() can be called without RTNL or RCU protection.

Use RCU protection to avoid potential UAF.

Fixes: 29a26a568038 ("netfilter: Pass struct net into the netfilter hooks")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/arp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index cb9a7ed8abd3ab17403f226ea7e31ea2bae52a9f..f23a1ec6694cb2f1bd60f28faa357fcad83c165a 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -659,10 +659,12 @@ static int arp_xmit_finish(struct net *net, struct sock *sk, struct sk_buff *skb
  */
 void arp_xmit(struct sk_buff *skb)
 {
+	rcu_read_lock();
 	/* Send it off, maybe filter it using firewalling first.  */
 	NF_HOOK(NFPROTO_ARP, NF_ARP_OUT,
-		dev_net(skb->dev), NULL, skb, NULL, skb->dev,
+		dev_net_rcu(skb->dev), NULL, skb, NULL, skb->dev,
 		arp_xmit_finish);
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(arp_xmit);
 
-- 
2.48.1.502.g6dc24dfdaf-goog