netdev - Re: [PATCH] netlink: fix netlink_change

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Message-Id: <20101024.162623.68142530.davem@davemloft.net>
Date:	Sun, 24 Oct 2010 16:26:23 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, johannes@...solutions.net,
	paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH] netlink: fix netlink_change_ngroups()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sun, 24 Oct 2010 16:27:10 +0200

> commit 6c04bb18ddd633 (netlink: use call_rcu for netlink_change_ngroups)
> used a somewhat convoluted and racy way to perform call_rcu().
> 
> The old block of memory is freed after a grace period, but the rcu_head
> used to track it is located in new block.
> 
> This can clash if we call two times or more netlink_change_ngroups(),
> and a block is freed before another. call_rcu() called on different cpus
> makes no guarantee in order of callbacks.
> 
> Fix this using a more standard way of handling this : Each block of
> memory contains its own rcu_head, so that no 'use after free' can
> happens.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>

Applied, thanks a lot.
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