linux-kernel - RE: [EXT] [PATCH net v2] ipv4: ip_gre: Avoid skb_pull() failure in ipgre

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Message-ID: <SJ0PR18MB5216A25BD74AE376FB1E536BDB87A@SJ0PR18MB5216.namprd18.prod.outlook.com>
Date:   Sun, 3 Dec 2023 06:58:19 +0000
From:   Suman Ghosh <sumang@...vell.com>
To:     Shigeru Yoshida <syoshida@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "dsahern@...nel.org" <dsahern@...nel.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] [PATCH net v2] ipv4: ip_gre: Avoid skb_pull() failure in
 ipgre_xmit()

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
>