ipv6: icmp: convert to dev_net_rcu()

JIRA: https://issues.redhat.com/browse/RHEL-115578

commit 34aef2b
Author: Eric Dumazet <edumazet@google.com>
Date:   Wed Feb 5 15:51:19 2025 +0000

    ipv6: icmp: convert to dev_net_rcu()

    icmp6_send() must acquire rcu_read_lock() sooner to ensure
    the dev_net() call done from a safe context.

    Other ICMPv6 uses of dev_net() seem safe, change them to
    dev_net_rcu() to get LOCKDEP support to catch bugs.

    Fixes: 9a43b70 ("[NETNS][IPV6] icmp6 - make icmpv6_socket per namespace")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Link: https://patch.msgid.link/20250205155120.1676781-12-edumazet@google.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

Author: CKI Backport Bot

net/ipv6/icmp.c

@@ -76,7 +76,7 @@ static int icmpv6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 {
 	/* icmpv6_notify checks 8 bytes can be pulled, icmp6hdr is 8 bytes */
 	struct icmp6hdr *icmp6 = (struct icmp6hdr *) (skb->data + offset);
-	struct net *net = dev_net(skb->dev);
+	struct net *net = dev_net_rcu(skb->dev);
 
 	if (type == ICMPV6_PKT_TOOBIG)
 		ip6_update_pmtu(skb, net, info, skb->dev->ifindex, 0, sock_net_uid(net, NULL));
@@ -473,7 +473,10 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 
 	if (!skb->dev)
 		return;
-	net = dev_net(skb->dev);
+
+	rcu_read_lock();
+
+	net = dev_net_rcu(skb->dev);
 	mark = IP6_REPLY_MARK(net, skb->mark);
 	/*
 	 *	Make sure we respect the rules
@@ -496,7 +499,7 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 		    !(type == ICMPV6_PARAMPROB &&
 		      code == ICMPV6_UNK_OPTION &&
 		      (opt_unrec(skb, info))))
-			return;
+			goto out;
 
 		saddr = NULL;
 	}
@@ -526,7 +529,7 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 	if ((addr_type == IPV6_ADDR_ANY) || (addr_type & IPV6_ADDR_MULTICAST)) {
 		net_dbg_ratelimited("icmp6_send: addr_any/mcast source [%pI6c > %pI6c]\n",
 				    &hdr->saddr, &hdr->daddr);
-		return;
+		goto out;
 	}
 
 	/*
@@ -535,7 +538,7 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 	if (is_ineligible(skb)) {
 		net_dbg_ratelimited("icmp6_send: no reply to icmp error [%pI6c > %pI6c]\n",
 				    &hdr->saddr, &hdr->daddr);
-		return;
+		goto out;
 	}
 
 	/* Needed by both icmpv6_global_allow and icmpv6_xmit_lock */
@@ -582,7 +585,7 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 	np = inet6_sk(sk);
 
 	if (!icmpv6_xrlim_allow(sk, type, &fl6, apply_ratelimit))
-		goto out;
+		goto out_unlock;
 
 	tmp_hdr.icmp6_type = type;
 	tmp_hdr.icmp6_code = code;
@@ -600,7 +603,7 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 
 	dst = icmpv6_route_lookup(net, skb, sk, &fl6);
 	if (IS_ERR(dst))
-		goto out;
+		goto out_unlock;
 
 	ipc6.hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);
 
@@ -616,7 +619,6 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 		goto out_dst_release;
 	}
 
-	rcu_read_lock();
 	idev = __in6_dev_get(skb->dev);
 
 	if (ip6_append_data(sk, icmpv6_getfrag, &msg,
@@ -630,13 +632,15 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 		icmpv6_push_pending_frames(sk, &fl6, &tmp_hdr,
 					   len + sizeof(struct icmp6hdr));
 	}
-	rcu_read_unlock();
+
 out_dst_release:
 	dst_release(dst);
-out:
+out_unlock:
 	icmpv6_xmit_unlock(sk);
 out_bh_enable:
 	local_bh_enable();
+out:
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(icmp6_send);
 
@@ -679,8 +683,8 @@ int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs, int type,
 	skb_pull(skb2, nhs);
 	skb_reset_network_header(skb2);
 
-	rt = rt6_lookup(dev_net(skb->dev), &ipv6_hdr(skb2)->saddr, NULL, 0,
-			skb, 0);
+	rt = rt6_lookup(dev_net_rcu(skb->dev), &ipv6_hdr(skb2)->saddr,
+			NULL, 0, skb, 0);
 
 	if (rt && rt->dst.dev)
 		skb2->dev = rt->dst.dev;
@@ -717,7 +721,7 @@ EXPORT_SYMBOL(ip6_err_gen_icmpv6_unreach);
 
 static enum skb_drop_reason icmpv6_echo_reply(struct sk_buff *skb)
 {
-	struct net *net = dev_net(skb->dev);
+	struct net *net = dev_net_rcu(skb->dev);
 	struct sock *sk;
 	struct inet6_dev *idev;
 	struct ipv6_pinfo *np;
@@ -832,7 +836,7 @@ enum skb_drop_reason icmpv6_notify(struct sk_buff *skb, u8 type,
 				   u8 code, __be32 info)
 {
 	struct inet6_skb_parm *opt = IP6CB(skb);
-	struct net *net = dev_net(skb->dev);
+	struct net *net = dev_net_rcu(skb->dev);
 	const struct inet6_protocol *ipprot;
 	enum skb_drop_reason reason;
 	int inner_offset;
@@ -889,7 +893,7 @@ enum skb_drop_reason icmpv6_notify(struct sk_buff *skb, u8 type,
 static int icmpv6_rcv(struct sk_buff *skb)
 {
 	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
-	struct net *net = dev_net(skb->dev);
+	struct net *net = dev_net_rcu(skb->dev);
 	struct net_device *dev = icmp6_dev(skb);
 	struct inet6_dev *idev = __in6_dev_get(dev);
 	const struct in6_addr *saddr, *daddr;
@@ -921,7 +925,7 @@ static int icmpv6_rcv(struct sk_buff *skb)
 		skb_set_network_header(skb, nh);
 	}
 
-	__ICMP6_INC_STATS(dev_net(dev), idev, ICMP6_MIB_INMSGS);
+	__ICMP6_INC_STATS(dev_net_rcu(dev), idev, ICMP6_MIB_INMSGS);
 
 	saddr = &ipv6_hdr(skb)->saddr;
 	daddr = &ipv6_hdr(skb)->daddr;
@@ -939,7 +943,7 @@ static int icmpv6_rcv(struct sk_buff *skb)
 
 	type = hdr->icmp6_type;
 
-	ICMP6MSGIN_INC_STATS(dev_net(dev), idev, type);
+	ICMP6MSGIN_INC_STATS(dev_net_rcu(dev), idev, type);
 
 	switch (type) {
 	case ICMPV6_ECHO_REQUEST:
@@ -1034,9 +1038,9 @@ static int icmpv6_rcv(struct sk_buff *skb)
 
 csum_error:
 	reason = SKB_DROP_REASON_ICMP_CSUM;
-	__ICMP6_INC_STATS(dev_net(dev), idev, ICMP6_MIB_CSUMERRORS);
+	__ICMP6_INC_STATS(dev_net_rcu(dev), idev, ICMP6_MIB_CSUMERRORS);
 discard_it:
-	__ICMP6_INC_STATS(dev_net(dev), idev, ICMP6_MIB_INERRORS);
+	__ICMP6_INC_STATS(dev_net_rcu(dev), idev, ICMP6_MIB_INERRORS);
 drop_no_count:
 	kfree_skb_reason(skb, reason);
 	return 0;