Re: [PATCH] net/ipv6/exthdrs.c et al: Optional strict PadN option checking

[Eldad Zack]

On 12 April 2012 22:00, David Miller <davem@xxxxxxxxxxxxx> wrote:
>> Added strict checking of PadN. PadN can be used to increase header
>> size and thus push the protocol header into the 2nd fragment.
>>
>> PadN is used to align the options within the Hop-by-Hop or
>> Destination Options header to 64-bit boundaries. The maximum valid
>> size is thus 7 bytes.
>> RFC 4942 recommends to actively check the "payload" itself and
>> ensure that it contains only zeroes.
> I think you should do away with the sysctl and always perform these
> checks.
>
> At the very leat, the optlen > 7 check should always be performed.
> And frankly the pad byte being zero check makes sense to do all the
> time as far as I can tell too.

That's the way I see it, as was my initial intent. Then I got
concerned with the possibility that a communication with
slightly-broken stack implementation (e.g., unsanitized buffers) would
fail without the user being able to control it at runtime.
Do you consider this a non-issue?

If not, please apply the (soon to be sent) patch.

Thanks,
Eldad
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/