netdev - Re: [PATCH v2 net] net: Revert "net: avoid one atomic operation in skb

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Message-Id: <20141121.152707.1184550321197091769.davem@davemloft.net>
Date:	Fri, 21 Nov 2014 15:27:07 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	sd@...asysnail.net, clm@...com, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net] net: Revert "net: avoid one atomic operation in
 skb_clone()"

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 21 Nov 2014 11:47:16 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Not sure what I was thinking, but doing anything after
> releasing a refcount is suicidal or/and embarrassing.
> 
> By the time we set skb->fclone to SKB_FCLONE_FREE, another cpu
> could have released last reference and freed whole skb.
> 
> We potentially corrupt memory or trap if CONFIG_DEBUG_PAGEALLOC is set.
> 
> Reported-by: Chris Mason <clm@...com>
> Fixes: ce1a4ea3f1258 ("net: avoid one atomic operation in skb_clone()")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Sabrina Dubroca <sd@...asysnail.net>
> ---
> v2: the revert went wrong, as SKB_FCLONE_UNAVAILABLE
>     was later replaced by SKB_FCLONE_FREE, spotted by Sabrina Dubroca

Applied, thanks Eric.
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