linux-kernel - Re: [PATCH] gainfar.c : skb_over

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Message-ID: <4C2855D4.5050507@extricom.com>
Date:	Mon, 28 Jun 2010 10:57:08 +0300
From:	Eran Liberty <liberty@...ricom.com>
To:	David Miller <davem@...emloft.net>
CC:	linux-kernel@...r.kernel.org, galak@...nel.crashing.org
Subject: Re: [PATCH] gainfar.c : skb_over_panic (kernel-2.6.32.15)

David Miller wrote:
> From: Eran Liberty <liberty@...ricom.com>
> Date: Thu, 24 Jun 2010 12:53:23 +0300
>
>   
>> Fix possible skb_over_panic event in Freescale's "gianfar" driver. 
>>
>> The skb_over_panic occurs due to calling skb_put() within
>> gfar_clean_rx_ring(). This happens if (and only if) shortly prior to
>> the event and a few lined above the skb_put(), an skb was queued back
>> to the priv->rx_recycle queue due to RXBD_LAST or RXBD_ERR status.
>> The skb is queued without properly re-setting its state.
>>
>> The patch properly reset the skb state.
>>
>> I have tested this patch on MPC8548 based product and asserted it
>> avoided the skb_over_panic event.
>>
>> Signed-off-by: Eran Liberty <liberty@...ricom.com>
>>     
>
> Eran, this seems to be fixed already.  The code in the current
> tree now reads:
>
> 				/*
> 				 * We need to un-reserve() the skb to what it
> 				 * was before gfar_new_skb() re-aligned
> 				 * it to an RXBUF_ALIGNMENT boundary
> 				 * before we put the skb back on the
> 				 * recycle list.
> 				 */
> 				skb_reserve(skb, -GFAR_CB(skb)->alignamount);
> 				__skb_queue_head(&priv->rx_recycle, skb);
>
>
>   
This code has proved to be insufficient and produce skb_over_panic. The 
proposed patch fix this.

-- Liberty

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