From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	"thomas.petazzoni@bootlin.com, netdev@vger.kernel.org,  linux-kernel@vger.kernel.org, Miguel Gazquez" <miguel.gazquez@bootlin.com>,
	Eric Dumazet <edumazet@google.com>,
	David Ahern <dsahern@kernel.org>,
	Jakub Kicinski <kuba@kernel.org>,
	Miguel Gazquez <miguel.gazquez@bootlin.com>
Subject: [PATCH 6.12 189/220] ipv4: start using dst_dev_rcu()
Date: Thu, 20 Aug 2026 16:56:19 +0200
Message-ID: <20260820145229.195230707@linuxfoundation.org>
In-Reply-To: <20260820145223.480031205@linuxfoundation.org>
References: <20260820145223.480031205@linuxfoundation.org>
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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 6ad8de3cefdb6ffa6708b21c567df0dbf82c43a8 ]

Change icmpv4_xrlim_allow(), ip_defrag() to prevent possible UAF.

Change ipmr_prepare_xmit(), ipmr_queue_fwd_xmit(), ip_mr_output(),
ipv4_neigh_lookup() to use lockdep enabled dst_dev_rcu().

Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20250828195823.3958522-9-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ minor modifications to fix conflict ]
Signed-off-by: Miguel Gazquez <miguel.gazquez@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/icmp.c        |    6 +++---
 net/ipv4/ip_fragment.c |    6 ++++--
 net/ipv4/ipmr.c        |    4 ++--
 net/ipv4/route.c       |    4 ++--
 4 files changed, 11 insertions(+), 9 deletions(-)

--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -320,17 +320,17 @@ static bool icmpv4_xrlim_allow(struct ne
 		return true;
 
 	/* No rate limit on loopback */
-	dev = dst_dev(dst);
+	rcu_read_lock();
+	dev = dst_dev_rcu(dst);
 	if (dev && (dev->flags & IFF_LOOPBACK))
 		goto out;
 
-	rcu_read_lock();
 	peer = inet_getpeer_v4(net->ipv4.peers, fl4->daddr,
 			       l3mdev_master_ifindex_rcu(dev));
 	rc = inet_peer_xrlim_allow(peer,
 				   READ_ONCE(net->ipv4.sysctl_icmp_ratelimit));
-	rcu_read_unlock();
 out:
+	rcu_read_unlock();
 	if (!rc)
 		__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
 	else
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -483,13 +483,15 @@ out_fail:
 /* Process an incoming IP datagram fragment. */
 int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
 {
-	struct net_device *dev = skb->dev ? : skb_dst_dev(skb);
-	int vif = l3mdev_master_ifindex_rcu(dev);
+	struct net_device *dev;
 	struct ipq *qp;
+	int vif;
 
 	__IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);
 
 	/* Lookup (or create) queue header */
+	dev = skb->dev ? : skb_dst_dev_rcu(skb);
+	vif = l3mdev_master_ifindex_rcu(dev);
 	qp = ip_find(net, ip_hdr(skb), user, vif);
 	if (qp) {
 		int ret;
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1906,7 +1906,7 @@ static void ipmr_queue_xmit(struct net *
 		goto out_free;
 	}
 
-	encap += LL_RESERVED_SPACE(dev) + rt->dst.header_len;
+	encap += LL_RESERVED_SPACE(dst_dev_rcu(&rt->dst)) + rt->dst.header_len;
 
 	if (skb_cow(skb, encap)) {
 		ip_rt_put(rt);
@@ -1943,7 +1943,7 @@ static void ipmr_queue_xmit(struct net *
 	 * result in receiving multiple packets.
 	 */
 	NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD,
-		net, NULL, skb, skb->dev, dev,
+		net, NULL, skb, skb->dev, dst_dev_rcu(&rt->dst),
 		ipmr_forward_finish);
 	return;
 
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -413,11 +413,11 @@ static struct neighbour *ipv4_neigh_look
 					   const void *daddr)
 {
 	const struct rtable *rt = container_of(dst, struct rtable, dst);
-	struct net_device *dev = dst_dev(dst);
+	struct net_device *dev;
 	struct neighbour *n;
 
 	rcu_read_lock();
-
+	dev = dst_dev_rcu(dst);
 	if (likely(rt->rt_gw_family == AF_INET)) {
 		n = ip_neigh_gw4(dev, rt->rt_gw4);
 	} else if (rt->rt_gw_family == AF_INET6) {