[ovs-dev] [PATCH 1/2] flow: Fix buffer overread for crafted IPv6 packets.

Darrell Ball dlu998 at gmail.com
Tue Jul 10 03:13:16 UTC 2018


Acked-by: Darrell Ball <dlu998 at gmail.com>

I never read the contents of that function; just assumed it was sanitizing
the packet :-)

On Mon, Jul 9, 2018 at 1:04 PM, Ben Pfaff <blp at ovn.org> wrote:

> The ipv6_sanity_check() function implemented a check for IPv6 payload
> length wrong: ip6_plen is the payload length but this function checked
> whether it was longer than the total length of IPv6 header plus payload.
> This meant that a packet with a crafted ip6_plen could result in a buffer
> overread of up to the length of an IPv6 header (40 bytes).
>
> The kernel datapath flow extraction code does not obviously have a similar
> problem.
>
> Reported-at: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9287
> Signed-off-by: Ben Pfaff <blp at ovn.org>
> ---
>  lib/flow.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/flow.c b/lib/flow.c
> index a785e63a82f3..76a8b9aaeaae 100644
> --- a/lib/flow.c
> +++ b/lib/flow.c
> @@ -677,7 +677,7 @@ ipv6_sanity_check(const struct ovs_16aligned_ip6_hdr
> *nh, size_t size)
>      }
>
>      plen = ntohs(nh->ip6_plen);
> -    if (OVS_UNLIKELY(plen > size)) {
> +    if (OVS_UNLIKELY(plen + IPV6_HEADER_LEN > size)) {
>          return false;
>      }
>      /* Jumbo Payload option not supported yet. */
> --
> 2.16.1
>
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