netdev - Re: net: Clone skb before setting peeked flag

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Message-Id: <20150715.161343.936469507696734723.davem@davemloft.net>
Date:	Wed, 15 Jul 2015 16:13:43 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	khlebnikov@...dex-team.ru, netdev@...r.kernel.org,
	edumazet@...gle.com
Subject: Re: net: Clone skb before setting peeked flag

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Mon, 13 Jul 2015 16:04:13 +0800

> Shared skbs must not be modified and this is crucial for broadcast
> and/or multicast paths where we use it as an optimisation to avoid
> unnecessary cloning.
> 
> The function skb_recv_datagram breaks this rule by setting peeked
> without cloning the skb first.  This causes funky races which leads
> to double-free.
> 
> This patch fixes this by cloning the skb and replacing the skb
> in the list when setting skb->peeked.
> 
> Fixes: a59322be07c9 ("[UDP]: Only increment counter on first peek/recv")
> Reported-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

Applied and queued up for -stable.
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