From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <shemminger@vyatta.com>
Subject: Re: [PATCH] netem: fix possible skb leak
Date: Mon, 30 Apr 2012 09:25:09 -0700
Message-ID: <20120430092509.54b89ae6@nehalam.linuxnetplumber.net>
References: <1335726502.3897.8.camel@edumazet-glaptop>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Cc: David Miller <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>,
	Stephen Hemminger <shemminger@osdl.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail.vyatta.com ([76.74.103.46]:34888 "EHLO mail.vyatta.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1756251Ab2D3QZS (ORCPT <rfc822;netdev@vger.kernel.org>);
	Mon, 30 Apr 2012 12:25:18 -0400
In-Reply-To: <1335726502.3897.8.camel@edumazet-glaptop>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Sun, 29 Apr 2012 21:08:22 +0200
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> From: Eric Dumazet <edumazet@google.com>
> 
> skb_checksum_help(skb) can return an error, we must free skb in this
> case. qdisc_drop(skb, sch) can also be feeded with a NULL skb (if
> skb_unshare() failed), so lets use this generic helper.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Stephen Hemminger <shemminger@osdl.org>
> ---
>  net/sched/sch_netem.c |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
> index 5da548f..ebd2296 100644
> --- a/net/sched/sch_netem.c
> +++ b/net/sched/sch_netem.c
> @@ -408,10 +408,8 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
>  	if (q->corrupt && q->corrupt >= get_crandom(&q->corrupt_cor)) {
>  		if (!(skb = skb_unshare(skb, GFP_ATOMIC)) ||
>  		    (skb->ip_summed == CHECKSUM_PARTIAL &&
> -		     skb_checksum_help(skb))) {
> -			sch->qstats.drops++;
> -			return NET_XMIT_DROP;
> -		}
> +		     skb_checksum_help(skb)))
> +			return qdisc_drop(skb, sch);
>  
>  		skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8);
>  	}
> 
> 

This would crater if skb_unshare() returned NULL. I think the conditional
needs to be split into two paths.