xfrm: Fix the usage of skb->sk

JIRA: https://issues.redhat.com/browse/RHEL-84576

commit 1620c88
Author: Steffen Klassert <steffen.klassert@secunet.com>
Date:   Thu Jan 16 11:46:03 2025 +0100

    xfrm: Fix the usage of skb->sk

    xfrm assumed to always have a full socket at skb->sk.
    This is not always true, so fix it by converting to a
    full socket before it is used.

    Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
    Reviewed-by: Eric Dumazet <edumazet@google.com>

Signed-off-by: Sabrina Dubroca <sdubroca@redhat.com>

Author: Sabrina Dubroca

net/ipv4/esp4.c

@@ -280,7 +280,7 @@ static void esp_output_done(struct crypto_async_request *base, int err)
 		    x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
 			esp_output_tail_tcp(x, skb);
 		else
-			xfrm_output_resume(skb->sk, skb, err);
+			xfrm_output_resume(skb_to_full_sk(skb), skb, err);
 	}
 }
 

net/ipv6/esp6.c

@@ -315,7 +315,7 @@ static void esp_output_done(struct crypto_async_request *base, int err)
 		    x->encap && x->encap->encap_type == TCP_ENCAP_ESPINTCP)
 			esp_output_tail_tcp(x, skb);
 		else
-			xfrm_output_resume(skb->sk, skb, err);
+			xfrm_output_resume(skb_to_full_sk(skb), skb, err);
 	}
 }
 

net/ipv6/xfrm6_output.c

@@ -82,14 +82,14 @@ static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 
 	toobig = skb->len > mtu && !skb_is_gso(skb);
 
-	if (toobig && xfrm6_local_dontfrag(skb->sk)) {
+	if (toobig && xfrm6_local_dontfrag(sk)) {
 		xfrm6_local_rxpmtu(skb, mtu);
 		kfree_skb(skb);
 		return -EMSGSIZE;
 	} else if (toobig && xfrm6_noneed_fragment(skb)) {
 		skb->ignore_df = 1;
 		goto skip_frag;
-	} else if (!skb->ignore_df && toobig && skb->sk) {
+	} else if (!skb->ignore_df && toobig && sk) {
 		xfrm_local_error(skb, mtu);
 		kfree_skb(skb);
 		return -EMSGSIZE;

net/xfrm/xfrm_interface_core.c

@@ -461,7 +461,7 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
 	skb_dst_set(skb, dst);
 	skb->dev = tdev;
 
-	err = dst_output(xi->net, skb->sk, skb);
+	err = dst_output(xi->net, skb_to_full_sk(skb), skb);
 	if (net_xmit_eval(err) == 0) {
 		dev_sw_netstats_tx_add(dev, 1, length);
 	} else {

net/xfrm/xfrm_output.c

@@ -796,7 +796,7 @@ static int xfrm4_tunnel_check_size(struct sk_buff *skb)
 	     !skb_gso_validate_network_len(skb, ip_skb_dst_mtu(skb->sk, skb)))) {
 		skb->protocol = htons(ETH_P_IP);
 
-		if (skb->sk)
+		if (skb->sk && sk_fullsock(skb->sk))
 			xfrm_local_error(skb, mtu);
 		else
 			icmp_send(skb, ICMP_DEST_UNREACH,
@@ -832,6 +832,7 @@ static int xfrm6_tunnel_check_size(struct sk_buff *skb)
 {
 	int mtu, ret = 0;
 	struct dst_entry *dst = skb_dst(skb);
+	struct sock *sk = skb_to_full_sk(skb);
 
 	if (skb->ignore_df)
 		goto out;
@@ -846,9 +847,9 @@ static int xfrm6_tunnel_check_size(struct sk_buff *skb)
 		skb->dev = dst->dev;
 		skb->protocol = htons(ETH_P_IPV6);
 
-		if (xfrm6_local_dontfrag(skb->sk))
+		if (xfrm6_local_dontfrag(sk))
 			ipv6_stub->xfrm6_local_rxpmtu(skb, mtu);
-		else if (skb->sk)
+		else if (sk)
 			xfrm_local_error(skb, mtu);
 		else
 			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);

net/xfrm/xfrm_policy.c

@@ -2910,7 +2910,7 @@ static void xfrm_policy_queue_process(struct timer_list *t)
 		skb_dst_drop(skb);
 		skb_dst_set(skb, dst);
 
-		dst_output(net, skb->sk, skb);
+		dst_output(net, skb_to_full_sk(skb), skb);
 	}
 
 out: