netdev - Re: net-next kernel NULL pointer dereference at fib_rules

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Date:	Tue, 10 Jul 2012 19:25:01 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	ogerlitz@...lanox.com, netdev@...r.kernel.org,
	shlomop@...lanox.com, amirv@...lanox.com, erezsh@...lanox.com
Subject: Re: net-next kernel NULL pointer dereference at fib_rules_tclass

On Tue, 2012-07-10 at 09:44 -0700, David Miller wrote:
> From: Or Gerlitz <ogerlitz@...lanox.com>
> Date: Tue, 10 Jul 2012 10:16:55 +0300
> 
> > Starting system logger: BUG: unable to handle kernel NULL pointer dereference at 00000000000000ac
> > IP: [<ffffffff81320393>] fib_rules_tclass+0xf/0x17
> 
> Ok, fib_rules_tclass() checks for res->r being NULL and only
> dereferences it if it is not.
> 
> fib4_rule->tclassid has offset ~0x8c on x86-64, and this fault
> address is 0x10 bytes off.
> 
> Does this patch fix the problem?
> 
> diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
> index 539c672..000c467 100644
> --- a/include/net/ip_fib.h
> +++ b/include/net/ip_fib.h
> @@ -230,6 +230,7 @@ static inline int fib_lookup(struct net *net, struct flowi4 *flp,
>  			     struct fib_result *res)
>  {
>  	if (!net->ipv4.fib_has_custom_rules) {
> +		res->r = NULL;
>  		if (net->ipv4.fib_local &&
>  		    !fib_table_lookup(net->ipv4.fib_local, flp, res,
>  				      FIB_LOOKUP_NOREF))

It does here, thanks


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