diff --git a/drivers/media/dvb-frontends/dib9000.c b/drivers/media/dvb-frontends/dib9000.c
index e540cfb13bac4b15dbfa06d1c050e0ad1246fcd0..f75dec4437835efd4e42c54496e9eb6a4f29b96d 100644
--- a/drivers/media/dvb-frontends/dib9000.c
+++ b/drivers/media/dvb-frontends/dib9000.c
@@ -1040,13 +1040,18 @@ static int dib9000_risc_apb_access_write(struct dib9000_state *state, u32 addres
 	if (address >= 1024 || !state->platform.risc.fw_is_running)
 		return -EINVAL;
 
+	if (len > 18)
+		return -EINVAL;
+
 	/* dprintk( "APB access thru wr fw %d %x", address, attribute); */
 
-	mb[0] = (unsigned short)address;
-	for (i = 0; i < len && i < 20; i += 2)
-		mb[1 + (i / 2)] = (b[i] << 8 | b[i + 1]);
+	mb[0] = (u16)address;
+	for (i = 0; i + 1 < len; i += 2)
+		mb[1 + i / 2] = b[i] << 8 | b[i + 1];
+	if (len & 1)
+		mb[1 + len / 2] = b[len - 1] << 8;
 
-	dib9000_mbx_send_attr(state, OUT_MSG_BRIDGE_APB_W, mb, 1 + len / 2, attribute);
+	dib9000_mbx_send_attr(state, OUT_MSG_BRIDGE_APB_W, mb, (3 + len) / 2, attribute);
 	return dib9000_mbx_get_message_attr(state, IN_MSG_END_BRIDGE_APB_RW, mb, &s, attribute) == 1 ? 0 : -EINVAL;
 }