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

[Greg KH]

-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Ang Way Chuang <wcang@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 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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