Bluetooth: Fix NULL pointer deference on eir_get_service_data

The len parameter is considered optional so it can be NULL so it cannot
be used for skipping to next entry of EIR_SERVICE_DATA.

Fixes: 8f9ae5b ("Bluetooth: eir: Add helpers for managing service data")
Signed-off-by: Luiz Augusto von Dentz <[email protected]>

Author: Vudentz

net/bluetooth/eir.c

@@ -366,17 +366,19 @@ u8 eir_create_scan_rsp(struct hci_dev *hdev, u8 instance, u8 *ptr)
 
 void *eir_get_service_data(u8 *eir, size_t eir_len, u16 uuid, size_t *len)
 {
-	while ((eir = eir_get_data(eir, eir_len, EIR_SERVICE_DATA, len))) {
+	size_t dlen;
+
+	while ((eir = eir_get_data(eir, eir_len, EIR_SERVICE_DATA, &dlen))) {
 		u16 value = get_unaligned_le16(eir);
 
 		if (uuid == value) {
 			if (len)
-				*len -= 2;
+				*len = dlen - 2;
 			return &eir[2];
 		}
 
-		eir += *len;
-		eir_len -= *len;
+		eir += dlen;
+		eir_len -= dlen;
 	}
 
 	return NULL;