netdev - 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 16:47:21 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     David Ahern <dsa@...ulusnetworks.com>,
        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 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;