Subject: Re: [PATCH] ipv4: fix the rcu race between free_fib_info and
 ip_route_output_slow
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Cc: David Miller <davem@davemloft.net>, kunx.jiang@intel.com,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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Date: Wed, 23 May 2012 08:43:33 +0200
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On Wed, 2012-05-23 at 08:37 +0200, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>

> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index ffcb3b0..b56b91e 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -2127,7 +2127,7 @@ static int __mkroute_input(struct sk_buff *skb,
>  	u32 itag;
>  
>  	/* get a working reference to the output device */
> -	out_dev = __in_dev_get_rcu(FIB_RES_DEV(*res));
> +	out_dev = __in_dev_get_rcu(rcu_dereference(FIB_RES_DEV(*res)));

This part might need additional fix (if FIB_RES_DEV(*res) is NULL),
because __in_dev_get_rcu() could crash dereferencing NULL pointer.


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