Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone

From	Dmitry Vyukov <dvyukov@google.com>
Newsgroups	linux.kernel
Subject	Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone
Date	2017-03-05 12:00 +0100
Message-ID	<thC3n-7vd-1@gated-at.bofh.it> (permalink)
References	<tgZlo-4ue-29@gated-at.bofh.it> <th0U9-5DA-11@gated-at.bofh.it> <thn4l-51S-5@gated-at.bofh.it> <thojL-630-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Sat, Mar 4, 2017 at 9:15 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>> > On 3/3/17 6:39 AM, Dmitry Vyukov wrote:
>> >> I am getting heap out-of-bounds reports in
>> >> fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone while running
>> >> syzkaller fuzzer on 86292b33d4b79ee03e2f43ea0381ef85f077c760. They all
>> >> follow the same pattern: an object of size 216 is allocated from
>> >> ip_dst_cache slab, and then accessed at offset 272/276 withing
>> >> fib6_walk. Looks like type confusion. Unfortunately this is not
>> >> reproducible.
>> >
>> > I'll take a look this weekend or Monday at the latest.
>>
>>
>> I've got some additional useful info on this. I think this is
>> use-after-free rather than out-of-bounds. I've collected stack where
>> the route was disposed with call_rcu, see the last "Disposed" stack.
>> The crash happens when cmpxchg in rt_cache_route replaces an existing
>> route. And that route seems to have some existing pointers to it
>> (rt->dst.rt6_next) which fib6_walk uses to get to it after its
>> deletion.
>
> rt_cache_route() deals with IPv4 routes.
>
> We somehow mix IPv4 and IPv6 dsts in IPv6 tree.
>
> We need to add type safety at IPV6 route insertions to catch the
> offender.


If you suggest additional checks, I will collect stacks.

Thread

net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-03 18:40 +0100
  Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-03 20:20 +0100
  Re: net: heap out-of-bounds in  fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone David Ahern <dsa@cumulusnetworks.com> - 2017-03-03 20:50 +0100
    Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-04 20:00 +0100
      Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-04 20:10 +0100
      Re: net: heap out-of-bounds in  fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-04 21:20 +0100
        Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-05 12:00 +0100
        Re: net: heap out-of-bounds in  fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone David Ahern <dsa@cumulusnetworks.com> - 2017-03-06 18:40 +0100
          Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-06 20:00 +0100
            Re: net: heap out-of-bounds in  fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone David Ahern <dsa@cumulusnetworks.com> - 2017-03-07 01:00 +0100
              Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 09:50 +0100
                Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 11:30 +0100
                Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 19:20 +0100
                Re: net: heap out-of-bounds in  fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone David Ahern <dsa@cumulusnetworks.com> - 2017-03-07 19:50 +0100
                Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 20:20 +0100
                Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 20:50 +0100
                Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 21:10 +0100
                Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-08 13:30 +0100
                Re: net: heap out-of-bounds in  fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone David Ahern <dsa@cumulusnetworks.com> - 2017-03-08 05:50 +0100
                Re: net: heap out-of-bounds in fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone Dmitry Vyukov <dvyukov@google.com> - 2017-03-07 18:50 +0100
                Re: net: heap out-of-bounds in  fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone David Ahern <dsa@cumulusnetworks.com> - 2017-03-07 18:50 +0100
                Re: net: heap out-of-bounds in  fib6_clean_node/rt6_fill_node/fib6_age/fib6_prune_clone David Ahern <dsa@cumulusnetworks.com> - 2017-03-07 19:30 +0100

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