Re: [patch 29/37] dvb-core: Proper handling ULE SNDU length of 0

Ang Way Chuang
2006-09-08T13:11:18Z

Michael Krufky wrote:
> Greg KH wrote:
>> -stable review patch. If anyone has any objections, please let us know.
>
> Greg,
>
> Can we hold off on this until the 2.6.17.13 review cycle? This patch
> has not been sent to the linux-dvb mailing list, it has not been
> reviewed or tested except for the Author and Marcel.
>
> Please also add me to the cc list for the stable patches review.
>
> DVB maintainers,
>
> Marcel expressed some concerns about this patch on LKML, see thread:
>
> http://lkml.org/lkml/2006/9/6/314
>
> He says that the code in our mercurial tree, and in 2.6.18-rcX does this
> in a much nicer way, but that it involves some major changes. If this
> patch seems acceptable, then we can apply it for 2.6.17.y, and the
> larger, more appropriate change will be seen when 2.6.18 gets released.
>
> I, myself, do not know enough about the internals of dvb_net ... but I
> think that we should agree to this patch before it gets applied to -stable
>
> Regards,
>
> Mike Krufky
>
>

Sorry for not forwarding this patch to linux-dvb mailing list in the first place.
My mistake. If this patch is okay after DVB maintainers have tested it, then
Adrian Bunk may find it useful for his 2.6.16.x tree.

Regards,
Ang Way Chuang

>>
>> ------------------
>> From: Ang Way Chuang <wcang@nrg.cs.usm.my>
>>
>> ULE (Unidirectional Lightweight Encapsulation RFC 4326) decapsulation
>> code has a bug that allows an attacker to send a malformed ULE packet
>> with SNDU length of 0 and bring down the receiving machine. This patch
>> fix the bug and has been tested on version 2.6.17.11. This bug is 100%
>> reproducible and the modified source code (GPL) used to produce this bug
>> will be posted on http://nrg.cs.usm.my/downloads.htm shortly. The
>> kernel will produce a dump during CRC32 checking on faulty ULE packet.
>>
>>
>> Signed-off-by: Ang Way Chuang <wcang@nrg.cs.usm.my>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
>>
>> ---
>> drivers/media/dvb/dvb-core/dvb_net.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> --- linux-2.6.17.11.orig/drivers/media/dvb/dvb-core/dvb_net.c
>> +++ linux-2.6.17.11/drivers/media/dvb/dvb-core/dvb_net.c
>> @@ -492,7 +492,8 @@ static void dvb_net_ule( struct net_devi
>> } else
>> priv->ule_dbit = 0;
>>
>> - if (priv->ule_sndu_len > 32763) {
>> + if (priv->ule_sndu_len > 32763 ||
>> + priv->ule_sndu_len < ((priv->ule_dbit) ? 4 : 4 + ETH_ALEN)) {
>> printk(KERN_WARNING "%lu: Invalid ULE SNDU length %u. "
>> "Resyncing.\n", priv->ts_count, priv->ule_sndu_len);
>> priv->ule_sndu_len = 0;
>>
>> --
>> -
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>
>