From: Eric Dumazet <edumazet@google.com>
Date: Fri, 7 Feb 2025 13:58:36 +0000 (+0000)
Subject: arp: use RCU protection in arp_xmit()
X-Git-Tag: v6.14-rc3~37^2~21^2~4
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=a42b69f692165ec39db42d595f4f65a4c8f42e44;p=linux-2.6-block.git

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@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250207135841.1948589-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index cb9a7ed8abd3..f23a1ec6694c 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);