netdev - Re: [PATCH v2 ipsec-next 1/2] xfrm: introduce forwarding of ICMP Error messages

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Date: Fri, 17 Nov 2023 10:13:15 +0100
From: Steffen Klassert <steffen.klassert@...unet.com>
To: Antony Antony <antony.antony@...unet.com>
CC: Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller"
	<davem@...emloft.net>, <devel@...ux-ipsec.org>, Jakub Kicinski
	<kuba@...nel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 ipsec-next 1/2] xfrm: introduce forwarding of ICMP
 Error messages

On Fri, Oct 27, 2023 at 10:16:29AM +0200, Antony Antony wrote:
> +
> +static struct sk_buff *xfrm_icmp_flow_decode(struct sk_buff *skb,
> +					     unsigned short family,
> +					     struct flowi *fl,
> +					     struct flowi *fl1)
> +{
> +	struct net *net = dev_net(skb->dev);
> +	struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
> +	int hl = family == AF_INET ? (sizeof(struct iphdr) +  sizeof(struct icmphdr)) :
> +		 (sizeof(struct ipv6hdr) + sizeof(struct icmp6hdr));
> +	skb_reset_network_header(newskb);

This is not needed there.

> +
> +	if (!pskb_pull(newskb, hl))
> +		return NULL;

This leaks newskb.

> +	skb_reset_network_header(newskb);
> +
> +	if (xfrm_decode_session_reverse(net, newskb, fl1, family) < 0) {
> +		kfree_skb(newskb);

The newskb is not dropped because of an error, maybe better use
consume_skb().

> +		XFRM_INC_STATS(net, LINUX_MIB_XFRMINHDRERROR);

This might bump a second stat counter for this packet. Also
this is not really an error, because you just can't parse
the payload of the icmp packet.

> +		return NULL;
> +	}
> +
> +	fl1->flowi_oif = fl->flowi_oif;
> +	fl1->flowi_mark = fl->flowi_mark;
> +	fl1->flowi_tos = fl->flowi_tos;
> +	nf_nat_decode_session(newskb, fl1, family);
> +
> +	return newskb;

Why do you return newskb here? It is not used in all
of the calling functions.

The rest looks good, thanks!