netdev - Re: [PATCH] bridge: Reset IPCB on forward non-local packets in br_handle_frame

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Date:	Wed, 2 Nov 2011 12:31:06 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Vasily Averin <vvs@...allels.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
	Herbert Xu <herbert@...dor.hengli.com.au>, devel@...nvz.org
Subject: Re: [PATCH] bridge: Reset IPCB on forward non-local packets in
 br_handle_frame_finish()

On Wed, 02 Nov 2011 23:08:57 +0400
Vasily Averin <vvs@...allels.com> wrote:

> if dst is not local br_handle_frame_finish() does not clone original skb and
> forgets to reset IPCB before return to IP stack. it can lead to stack corruption
> in icmp_send()
> 
> Signed-off-by: Vasily Averin <vvs@...ru>
> ---
>  net/bridge/br_input.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index f06ee39..6be8d00 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -93,10 +93,11 @@ int br_handle_frame_finish(struct sk_buff *skb)
>  			skb2 = skb;
> 
>  		br->dev->stats.multicast++;
> -	} else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
> +	} else if ((dst = __br_fdb_get(br, dest)) != NULL) {
>  		skb2 = skb;
>  		/* Do not forward the packet since it's local. */
> -		skb = NULL;
> +		if (dst->is_local) {
> +			skb = NULL;
>  	}
> 
>  	if (skb) {

What kernel version are you using? There were several previous fixes
in br_netfilter to deal with this type of issue over the last year.


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