media: dvb-net: fix OOB access in ULE extension header tables

The ule_mandatory_ext_handlers[] and ule_optional_ext_handlers[] tables
in handle_one_ule_extension() are declared with 255 elements (valid
indices 0-254), but the index htype is derived from network-controlled
data as (ule_sndu_type & 0x00FF), giving a range of 0-255. When
htype equals 255, an out-of-bounds read occurs on the function pointer
table, and the OOB value may be called as a function pointer.

Add a bounds check on htype against the array size before either table
is accessed. Out-of-range values now cause the SNDU to be discarded.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Reported-by: Ariel Silver <[email protected]>
Signed-off-by: Ariel Silver <[email protected]>
Cc: [email protected]
Signed-off-by: Mauro Carvalho Chehab <[email protected]>

Author: SilverPlate3

drivers/media/dvb-core/dvb_net.c

@@ -228,6 +228,9 @@ static int handle_one_ule_extension( struct dvb_net_priv *p )
 	unsigned char hlen = (p->ule_sndu_type & 0x0700) >> 8;
 	unsigned char htype = p->ule_sndu_type & 0x00FF;
 
+	if (htype >= ARRAY_SIZE(ule_mandatory_ext_handlers))
+		return -1;
+
 	/* Discriminate mandatory and optional extension headers. */
 	if (hlen == 0) {
 		/* Mandatory extension header */