netdev - Re: [PATCH] netfilter: fix race in conntrack between dump

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Message-ID: <20101130092803.53fde6af@nehalam>
Date:	Tue, 30 Nov 2010 09:28:03 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	David Miller <davem@...emloft.net>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Patrick McHardy <kaber@...sh.net>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH] netfilter:  fix  race in conntrack between dump_table
 and destroy

On Fri, 26 Nov 2010 13:51:01 -0800
Stephen Hemminger <shemminger@...tta.com> wrote:

> The netlink interface to dump the connection tracking table has a race
> when entries are deleted at the same time. A customer reported a crash 
> and the backtrace showed thatctnetlink_dump_table was running while a 
> conntrack entry wasbeing destroyed.
> (see https://bugzilla.vyatta.com/show_bug.cgi?id=6402).
> 
> According to RCU documentation, when using hlist_nulls the reader
> must handle the case of seeing a deleted entry and not proceed
> further down the linked list.  The old code would continue
> which caused the scan to walk into the free list. 
> 
> This patch uses locking (rather than RCU) for this operation which
> is guaranteed safe, and no longer requires getting reference while
> doing dump operation.
> 
> Signed-off-by: Stephen Hemminger <shemminger@...tta.com>

This should go in net-2.6 and stable for 2.6.32, 2.6.35, and 2.6.36



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