netdev - Re: [PATCH] netpoll: fix netpoll_send

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Message-Id: <20120613.155802.1121407188815452311.davem@davemloft.net>
Date:	Wed, 13 Jun 2012 15:58:02 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, bogdan.hamciuc@...escale.com,
	herbert@...dor.apana.org.au, nhorman@...driver.com
Subject: Re: [PATCH] netpoll: fix netpoll_send_udp() bugs

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 13 Jun 2012 07:30:21 +0200

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Bogdan Hamciuc diagnosed and fixed following bug in netpoll_send_udp() :
> 
> "skb->len += len;" instead of "skb_put(skb, len);"
> 
> Meaning that _if_ a network driver needs to call skb_realloc_headroom(),
> only packet headers would be copied, leaving garbage in the payload.
> 
> However the skb_realloc_headroom() must be avoided as much as possible
> since it requires memory and netpoll tries hard to work even if memory
> is exhausted (using a pool of preallocated skbs)
> 
> It appears netpoll_send_udp() reserved 16 bytes for the ethernet header,
> which happens to work for typicall drivers but not all.
> 
> Right thing is to use LL_RESERVED_SPACE(dev)
> (And also add dev->needed_tailroom of tailroom)
> 
> This patch combines both fixes.
> 
> Many thanks to Bogdan for raising this issue.
> 
> Reported-by: Bogdan Hamciuc <bogdan.hamciuc@...escale.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Tested-by: Bogdan Hamciuc <bogdan.hamciuc@...escale.com>

Applied and queued up for -stable, thanks Eric.
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