netdev - Re: 2.6.38.2, kernel panic, probably related to framentation handling

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Message-Id: <20110504.140533.35050081.davem@davemloft.net>
Date:	Wed, 04 May 2011 14:05:33 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	denys@...p.net.lb, netdev@...r.kernel.org
Subject: Re: 2.6.38.2, kernel panic, probably related to framentation
 handling

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Wed, 04 May 2011 22:02:26 +0200

> [PATCH] net: ip_expire() must revalidate route
> 
> Commit 4a94445c9a5c (net: Use ip_route_input_noref() in input path)
> added a bug in IP defragmentation handling, in case timeout is fired.
> 
> When a frame is defragmented, we use last skb dst field when building
> final skb. Its dst is valid, since we are in rcu read section.
> 
> But if a timeout occurs, we take first queued fragment to build one ICMP
> TIME EXCEEDED message. Problem is all queued skb have weak dst pointers,
> since we escaped RCU critical section after their queueing. icmp_send()
> might dereference a now freed (and possibly reused) part of memory.
> 
> Calling skb_dst_drop() and ip_route_input_noref() to revalidate route is
> the only possible choice.
> 
> Reported-by: Denys Fedoryshchenko <denys@...p.net.lb>
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
> ---

Applied to net-2.6 and queued up for -stable, thanks Eric!
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