V4L/DVB: dvb-core: Fix ULE decapsulation bug

Fix ULE decapsulation bug when less than 4 bytes of ULE SNDU is packed
into the remaining bytes of a MPEG2-TS frame

ULE (Unidirectional Lightweight Encapsulation RFC 4326) decapsulation
code has a bug that incorrectly treats ULE SNDU packed into the
remaining 2 or 3 bytes of a MPEG2-TS frame as having invalid pointer
field on the subsequent MPEG2-TS frame.
Signed-off-by: Ang Way Chuang <wcang@nav6.org>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/dvb-core/dvb_net.c

@@ -351,6 +351,7 @@ static void dvb_net_ule( struct net_device *dev, const u8 *buf, size_t buf_len )
 	const u8 *ts, *ts_end, *from_where = NULL;
 	u8 ts_remain = 0, how_much = 0, new_ts = 1;
 	struct ethhdr *ethh = NULL;
+	bool error = false;
 
 #ifdef ULE_DEBUG
 	/* The code inside ULE_DEBUG keeps a history of the last 100 TS cells processed. */
@@ -460,10 +461,16 @@ static void dvb_net_ule( struct net_device *dev, const u8 *buf, size_t buf_len )
 
 						/* Drop partly decoded SNDU, reset state, resync on PUSI. */
 						if (priv->ule_skb) {
-							dev_kfree_skb( priv->ule_skb );
+							error = true;
+							dev_kfree_skb(priv->ule_skb);
+						}
+
+						if (error || priv->ule_sndu_remain) {
 							dev->stats.rx_errors++;
 							dev->stats.rx_frame_errors++;
+							error = false;
 						}
+
 						reset_ule(priv);
 						priv->need_pusi = 1;
 						continue;
@@ -535,6 +542,7 @@ static void dvb_net_ule( struct net_device *dev, const u8 *buf, size_t buf_len )
 				from_where += 2;
 			}
 
+			priv->ule_sndu_remain = priv->ule_sndu_len + 2;
 			/*
 			 * State of current TS:
 			 *   ts_remain (remaining bytes in the current TS cell)
@@ -544,6 +552,7 @@ static void dvb_net_ule( struct net_device *dev, const u8 *buf, size_t buf_len )
 			 */
 			switch (ts_remain) {
 				case 1:
+					priv->ule_sndu_remain--;
 					priv->ule_sndu_type = from_where[0] << 8;
 					priv->ule_sndu_type_1 = 1; /* first byte of ule_type is set. */
 					ts_remain -= 1; from_where += 1;
@@ -557,6 +566,7 @@ static void dvb_net_ule( struct net_device *dev, const u8 *buf, size_t buf_len )
 				default: /* complete ULE header is present in current TS. */
 					/* Extract ULE type field. */
 					if (priv->ule_sndu_type_1) {
+						priv->ule_sndu_type_1 = 0;
 						priv->ule_sndu_type |= from_where[0];
 						from_where += 1; /* points to payload start. */
 						ts_remain -= 1;