netdev - Re: NULL pointer dereference in rt6_get

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Message-ID: <20151012203116.GC88112@canlin-mbp1.DHCP.thefacebook.com>
Date:	Mon, 12 Oct 2015 13:31:16 -0700
From:	Martin KaFai Lau <kafai@...com>
To:	Phil Sutter <phil@....cc>
CC:	<netdev@...r.kernel.org>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Julian Anastasov <ja@....bg>
Subject: Re: NULL pointer dereference in rt6_get_cookie()

On Sat, Oct 10, 2015 at 03:24:37PM +0200, Phil Sutter wrote:
> Using printk-debugging I could track down the problem to
> rt6_get_cookie() function in include/net/ip6_fib.h:
>
> The conditional at the start of the function evaluates true, since
> 'rt->rt6i_flags & RTF_PCPU' is non-zero. Due to that, 'rt' pointer is
> reassigned:
>
> | rt = (struct rt6_info *)(rt->dst.from);
>
> It appears that this effectively assigns NULL to it, and the following
> dereference causes the bug.
Thanks for the report.  I am looking into it.

--Martin
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