RE: [EXT] [PATCH net v2] ipv4: ip_gre: Avoid skb_pull() failure in ipgre_xmit()

[Suman Ghosh]

Hi Shigeru,

>diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index
>22a26d1d29a0..5169c3c72cff 100644
>--- a/net/ipv4/ip_gre.c
>+++ b/net/ipv4/ip_gre.c
>@@ -635,15 +635,18 @@ static netdev_tx_t ipgre_xmit(struct sk_buff *skb,
> 	}
>
> 	if (dev->header_ops) {
>+		int pull_len = tunnel->hlen + sizeof(struct iphdr);
>+
> 		if (skb_cow_head(skb, 0))
> 			goto free_skb;
>
> 		tnl_params = (const struct iphdr *)skb->data;
>
>-		/* Pull skb since ip_tunnel_xmit() needs skb->data pointing
>-		 * to gre header.
>-		 */
>-		skb_pull(skb, tunnel->hlen + sizeof(struct iphdr));
>+		if (!pskb_network_may_pull(skb, pull_len))
[Suman] Since this is transmit path, should we add unlikely() here?
>+			goto free_skb;
>+
>+		/* ip_tunnel_xmit() needs skb->data pointing to gre header. */
>+		skb_pull(skb, pull_len);
> 		skb_reset_mac_header(skb);
>
> 		if (skb->ip_summed == CHECKSUM_PARTIAL &&
>--
>2.41.0
>