bareudp: Pull inner IP header in bareudp_udp_encap_recv().

[ Upstream commit 45fa29c85117170b0508790f878b13ec6593c888 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c
index 43d038a5123e7ca82122dc613149606f138827b5..3fcd3b84a066e556fcffd0d57813613ae3e0cde1 100644 (file)
--- a/drivers/net/bareudp.c
+++ b/drivers/net/bareudp.c
@@ -60,6 +60,7 @@ 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)
@@ -137,10 +138,25 @@ 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