netdev - [PATCH net] vxlan: Pull inner IP header in vxlan_xmit

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Date: Wed, 29 May 2024 21:01:12 +0200
From: Guillaume Nault <gnault@...hat.com>
To: David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>
Cc: netdev@...r.kernel.org
Subject: [PATCH net] vxlan: Pull inner IP header in vxlan_xmit_one().

Ensure the inner IP header is part of the skb's linear data before
setting old_iph. Otherwise, on a fragmented skb, old_iph could point
outside of the packet data.

Use skb_vlan_inet_prepare() on classical VXLAN devices to accommodate
for potential VLANs. Use pskb_inet_may_pull() for VXLAN-GPE as there's
no Ethernet header in that case.

Signed-off-by: Guillaume Nault <gnault@...hat.com>
---
 drivers/net/vxlan/vxlan_core.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index f78dd0438843..323308734192 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -2339,7 +2339,7 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 	struct ip_tunnel_key *pkey;
 	struct ip_tunnel_key key;
 	struct vxlan_dev *vxlan = netdev_priv(dev);
-	const struct iphdr *old_iph = ip_hdr(skb);
+	const struct iphdr *old_iph;
 	struct vxlan_metadata _md;
 	struct vxlan_metadata *md = &_md;
 	unsigned int pkt_len = skb->len;
@@ -2355,6 +2355,16 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 	bool xnet = !net_eq(vxlan->net, dev_net(vxlan->dev));
 	__be32 vni = 0;
 
+	if (flags & VXLAN_F_GPE) {
+		if (!pskb_inet_may_pull(skb))
+			goto drop;
+	} else {
+		if (!skb_vlan_inet_prepare(skb))
+			goto drop;
+	}
+
+	old_iph = ip_hdr(skb);
+
 	info = skb_tunnel_info(skb);
 	use_cache = ip_tunnel_dst_cache_usable(skb, info);
 
-- 
2.39.2