netdev - Re: [PATCH v2] ipvs: Fix panic due to non-linear skb

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Date:	Sun, 25 May 2014 00:16:31 +0300 (EEST)
From:	Julian Anastasov <ja@....bg>
To:	Peter Christensen <pch@...bogen.com>
cc:	Wensong Zhang <wensong@...ux-vs.org>,
	Simon Horman <horms@...ge.net.au>, netdev@...r.kernel.org,
	lvs-devel@...r.kernel.org
Subject: Re: [PATCH v2] ipvs: Fix panic due to non-linear skb


	Hello,

On Sat, 24 May 2014, Peter Christensen wrote:

> Receiving a ICMP response to an IPIP packet in a non-linear skb could
> cause a kernel panic in __skb_pull.
> 
> The problem was introduced in
> commit f2edb9f7706dcb2c0d9a362b2ba849efe3a97f5e ("ipvs: implement
> passive PMTUD for IPIP packets").
> 
> Signed-off-by: Peter Christensen <pch@...bogen.com>

	Thanks!

Acked-by: Julian Anastasov <ja@....bg>

	Simon, please apply to ipvs tree!

> ---
>  net/netfilter/ipvs/ip_vs_core.c |   15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
> index 4f26ee4..3d2d2c8 100644
> --- a/net/netfilter/ipvs/ip_vs_core.c
> +++ b/net/netfilter/ipvs/ip_vs_core.c
> @@ -1392,15 +1392,19 @@ ip_vs_in_icmp(struct sk_buff *skb, int *related, unsigned int hooknum)
>  
>  	if (ipip) {
>  		__be32 info = ic->un.gateway;
> +		__u8 type = ic->type;
> +		__u8 code = ic->code;
>  
>  		/* Update the MTU */
>  		if (ic->type == ICMP_DEST_UNREACH &&
>  		    ic->code == ICMP_FRAG_NEEDED) {
>  			struct ip_vs_dest *dest = cp->dest;
>  			u32 mtu = ntohs(ic->un.frag.mtu);
> +			__be16 frag_off = cih->frag_off;
>  
>  			/* Strip outer IP and ICMP, go to IPIP header */
> -			__skb_pull(skb, ihl + sizeof(_icmph));
> +			if (pskb_pull(skb, ihl + sizeof(_icmph)) == NULL)
> +				goto ignore_ipip;
>  			offset2 -= ihl + sizeof(_icmph);
>  			skb_reset_network_header(skb);
>  			IP_VS_DBG(12, "ICMP for IPIP %pI4->%pI4: mtu=%u\n",
> @@ -1408,7 +1412,7 @@ ip_vs_in_icmp(struct sk_buff *skb, int *related, unsigned int hooknum)
>  			ipv4_update_pmtu(skb, dev_net(skb->dev),
>  					 mtu, 0, 0, 0, 0);
>  			/* Client uses PMTUD? */
> -			if (!(cih->frag_off & htons(IP_DF)))
> +			if (!(frag_off & htons(IP_DF)))
>  				goto ignore_ipip;
>  			/* Prefer the resulting PMTU */
>  			if (dest) {
> @@ -1427,12 +1431,13 @@ ip_vs_in_icmp(struct sk_buff *skb, int *related, unsigned int hooknum)
>  		/* Strip outer IP, ICMP and IPIP, go to IP header of
>  		 * original request.
>  		 */
> -		__skb_pull(skb, offset2);
> +		if (pskb_pull(skb, offset2) == NULL)
> +			goto ignore_ipip;
>  		skb_reset_network_header(skb);
>  		IP_VS_DBG(12, "Sending ICMP for %pI4->%pI4: t=%u, c=%u, i=%u\n",
>  			&ip_hdr(skb)->saddr, &ip_hdr(skb)->daddr,
> -			ic->type, ic->code, ntohl(info));
> -		icmp_send(skb, ic->type, ic->code, info);
> +			type, code, ntohl(info));
> +		icmp_send(skb, type, code, info);
>  		/* ICMP can be shorter but anyways, account it */
>  		ip_vs_out_stats(cp, skb);
>  
> -- 
> 1.7.10.4

Regards

--
Julian Anastasov <ja@....bg>
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