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

[Eric Dumazet]

On Sun, Dec 3, 2023 at 7:58 AM Suman Ghosh <sumang@xxxxxxxxxxx> wrote:
>
> 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?

Adding unlikely() is not needed, it is already done generically from
the inline helpers.

Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>