netdev - Re: [PATCH] ip: ip_options_compile() resilient to NULL skb route

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Date:	Thu, 14 Apr 2011 05:37:43 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hiroaki SHIMODA <shimoda.hiroaki@...il.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	David Miller <davem@...emloft.net>, lkml@...tdoyle.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH] ip: ip_options_compile() resilient to NULL skb route

Le jeudi 14 avril 2011 à 12:30 +0900, Hiroaki SHIMODA a écrit :
> On Thu, 14 Apr 2011 05:03:34 +0200
> Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
> > Le mercredi 13 avril 2011 à 19:54 -0700, Stephen Hemminger a écrit :
> > 
> > > I like this because it lets the bridge be transparent.
> > > The existing options code adds entry in record route, and which
> > > is not desirable.
> > 
> > OK then, I realize I should have submitted a full patch, here it is.
> > 
> > Thanks !
> > 
> > [PATCH] ip: ip_options_compile() resilient to NULL skb route
> > 
> > Scot Doyle demonstrated ip_options_compile() could be called with an skb
> > without an attached route, using a setup involving a bridge, netfilter,
> > and forged IP packets.
> > 
> > Let's make ip_options_compile() a bit more robust, instead of changing
> > bridge/netfilter code.
> 
> And ip_options_rcv_srr() in br_parse_ip_options() also 
> expects an skb with attached route, so below patch is needed ?
> 
> diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
> index 28a736f..3af1968 100644
> --- a/net/ipv4/ip_options.c
> +++ b/net/ipv4/ip_options.c
> @@ -603,7 +603,7 @@ int ip_options_rcv_srr(struct sk_buff *skb)
>  	unsigned long orefdst;
>  	int err;
>  
> -	if (!opt->srr)
> +	if (!opt->srr || !rt)
>  		return 0;
>  
>  	if (skb->pkt_type != PACKET_HOST)
> 
> Thanks.

Indeed good catch, but should we return 0 or -EINVAL so that caller can
drop packet ?

@@ -606,7 +606,7 @@ int ip_options_rcv_srr(struct sk_buff *skb)
 	if (!opt->srr)
 		return 0;
 
-	if (skb->pkt_type != PACKET_HOST)
+	if (skb->pkt_type != PACKET_HOST || !rt)
                return -EINVAL;
 	if (rt->rt_type == RTN_UNICAST) {
 		if (!opt->is_strictroute)


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