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 18:12:32 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     David Ahern <dsa@...ulusnetworks.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>,
        Cong Wang <xiyou.wangcong@...il.com>,
        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 6:09 PM, David Ahern <dsa@...ulusnetworks.com> wrote:
> On 4/18/17 2:43 PM, Andrey Konovalov wrote:
>> Hi!
>>
>> I've finally managed to reproduce one of the crashes on commit
>> 4f7d029b9bf009fbee76bb10c0c4351a1870d2f3 (4.11-rc7).
>>
>> I'm not sure if this bug has the same root cause as the first one
>> reported in this thread, but it definitely has to do with ipv6
>> routing.
>>
>> C reproducer, syzkaller program and my .config are attached.
>
> built a kernel with that config. booted the vm. ran the program. nada.
>
> strace is showing:
>
> clone(child_stack=0x72ffb0,
> flags=CLONE_NEWUTS|CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWNET) = -1 EINVAL
> (Invalid argument)
>

That's weird. I usually see this when I have CONFIG_USER_NS disabled.

Anyway, I just finished simplifying the reproducer. Give this one a try.

View attachment "ip6_rt_cache_alloc-crash-poc2.c" of type "text/x-csrc" (1586 bytes)