netdev - RE: [PATCH] net: Fix skb_under_panic oops in neigh_resolve

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Date:	Fri, 05 Oct 2012 18:59:43 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ramesh Nagappa <ramesh.nagappa@...csson.com>
Cc:	"ramesh.nagappa@...il.com" <ramesh.nagappa@...il.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
	"xemul@...allels.com" <xemul@...allels.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] net: Fix skb_under_panic oops in neigh_resolve_output

On Fri, 2012-10-05 at 12:33 -0400, Ramesh Nagappa wrote:
> Hi Eric,
> 
> Yes, that is a good optimization. neigh_resolve_output() also has the
> __skb_pull() outside the loop, is that required ? The changes would be
> like ...
> 
> neigh_resolve_output()
> ...
> -        __skb_pull(skb, skb_network_offset(skb));
> 
> 
>         if (!neigh_event_send(neigh, skb)) {
>                 int err;
>                 struct net_device *dev = neigh->dev;
>                 unsigned int seq;
> 
>                 if (dev->header_ops->cache && !neigh->hh.hh_len)
>                         neigh_hh_init(neigh, dst);
> 
>                 do {                        
> +			      __skb_pull(skb, skb_network_offset(skb));
>                         seq = read_seqbegin(&neigh->ha_lock);
>                         err = dev_hard_header(skb, dev, ntohs(skb->protocol),
>                                               neigh->ha, NULL, skb->len);
>                 } while (read_seqretry(&neigh->ha_lock, seq));

All similar constructions should be audited.

For example in net/decnet/dn_neigh.c , dn_neigh_output_packet()



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