linux-kernel - Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune

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Date:   Wed, 19 Apr 2017 17:51:44 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Mahesh Bandewar <maheshb@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: net: heap out-of-bounds in
 fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone

On 4/19/17 5:47 PM, Cong Wang wrote:
> On Wed, Apr 19, 2017 at 9:12 AM, Andrey Konovalov <andreyknvl@...gle.com> wrote:
>>
>> Anyway, I just finished simplifying the reproducer. Give this one a try.
> 
> Thanks for providing such a minimal reproducer!
> 
> The following patch could fix this crash, but I am not 100% sure if we should
> just clear these bits or reject them with an errno.
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 9db14189..cf524c2 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2086,7 +2086,7 @@ static struct rt6_info
> *ip6_route_info_create(struct fib6_config *cfg)
>         } else
>                 rt->rt6i_prefsrc.plen = 0;
> 
> -       rt->rt6i_flags = cfg->fc_flags;
> +       rt->rt6i_flags = cfg->fc_flags & ~(RTF_PCPU | RTF_CACHE);
> 
>  install_route:
>         rt->dst.dev = dev;
> 

I sent a patch returning EINVAL if RTF_PCPU is set in fc_flags