[media] firewire: firedtv-avc: potential buffer overflow

"program_info_length" is user controlled and can go up to 4095.  The
operand[] array has 509 bytes so we need to add a limit here to prevent
buffer overflows.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/firewire/firedtv-avc.c

@@ -1157,6 +1157,10 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
 		if (pmt_cmd_id != 1 && pmt_cmd_id != 4)
 			dev_err(fdtv->device,
 				"invalid pmt_cmd_id %d\n", pmt_cmd_id);
+		if (program_info_length > sizeof(c->operand) - write_pos) {
+			ret = -EINVAL;
+			goto out;
+		}
 
 		memcpy(&c->operand[write_pos], &msg[read_pos],
 		       program_info_length);
@@ -1180,6 +1184,11 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
 				dev_err(fdtv->device, "invalid pmt_cmd_id %d "
 					"at stream level\n", pmt_cmd_id);
 
+			if (es_info_length > sizeof(c->operand) - write_pos) {
+				ret = -EINVAL;
+				goto out;
+			}
+
 			memcpy(&c->operand[write_pos], &msg[read_pos],
 			       es_info_length);
 			read_pos += es_info_length;