diff mbox series

[net] ip_gre: validate csum_start only if CHECKSUM_PARTIAL

Message ID 20210902193447.94039-2-willemdebruijn.kernel@gmail.com
State New
Headers show
Series [net] ip_gre: validate csum_start only if CHECKSUM_PARTIAL | expand

Commit Message

Willem de Bruijn Sept. 2, 2021, 7:34 p.m. UTC 
From: Willem de Bruijn <willemb@google.com>

Only test integrity of csum_start if checksum offload is configured.

With checksum offload and GRE tunnel checksum, gre_build_header will
cheaply build the GRE checksum using local checksum offload. This
depends on inner packet csum offload, and thus that csum_start points
behind GRE. But validate this condition only with checksum offload.

Link: https://lore.kernel.org/netdev/YS+h%2FtqCJJiQei+W@shredder/
Fixes: 1d011c4803c7 ("ip_gre: add validation for csum_start")
Signed-off-by: Willem de Bruijn <willemb@google.com>
---
 net/ipv4/ip_gre.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 177d26d8fb9c..09311992a617 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -473,8 +473,11 @@  static void __gre_xmit(struct sk_buff *skb, struct net_device *dev,
 
 static int gre_handle_offloads(struct sk_buff *skb, bool csum)
 {
-	if (csum && skb_checksum_start(skb) < skb->data)
+	/* Local checksum offload requires csum offload of the inner packet */
+	if (csum && skb->ip_summed == CHECKSUM_PARTIAL &&
+	    skb_checksum_start(skb) < skb->data)
 		return -EINVAL;
+
 	return iptunnel_handle_offloads(skb, csum ? SKB_GSO_GRE_CSUM : SKB_GSO_GRE);
 }