bareudp: Pull inner IP header in bareudp_udp_encap_recv().

Bareudp reads the inner IP header to get the ECN value. Therefore, it
needs to ensure that it's part of the skb's linear data.

This is similar to the vxlan and geneve fixes for that same problem:
  * commit f7789419137b ("vxlan: Pull inner IP header in vxlan_rcv().")
  * commit 1ca1ba465e55 ("geneve: make sure to pull inner header in
    geneve_rx()")

Fixes: 571912c69f0e ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/5205940067c40218a70fbb888080466b2fc288db.1726046181.git.gnault@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
index 7aca0544fb29c9e78c692bffc43c9a0b1dc0d3e5..b4e820a123caf1e8a157229f233c7107aa021274 100644 (file)
--- a/drivers/net/bareudp.c
+++ b/drivers/net/bareudp.c
@@ -68,6 +68,7 @@ static int bareudp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
        __be16 proto;
        void *oiph;
        int err;
+       int nh;
 
        bareudp = rcu_dereference_sk_user_data(sk);
        if (!bareudp)
@@ -148,10 +149,25 @@ static int bareudp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
        }
        skb_dst_set(skb, &tun_dst->dst);
        skb->dev = bareudp->dev;
-       oiph = skb_network_header(skb);
-       skb_reset_network_header(skb);
        skb_reset_mac_header(skb);
 
+       /* Save offset of outer header relative to skb->head,
+        * because we are going to reset the network header to the inner header
+        * and might change skb->head.
+        */
+       nh = skb_network_header(skb) - skb->head;
+
+       skb_reset_network_header(skb);
+
+       if (!pskb_inet_may_pull(skb)) {
+               DEV_STATS_INC(bareudp->dev, rx_length_errors);
+               DEV_STATS_INC(bareudp->dev, rx_errors);
+               goto drop;
+       }
+
+       /* Get the outer header. */
+       oiph = skb->head + nh;
+
        if (!ipv6_mod_enabled() || family == AF_INET)
                err = IP_ECN_decapsulate(oiph, skb);
        else