Bluetooth: eir: Fix possible crashes on eir_create_adv_data

eir_create_adv_data may attempt to add EIR_FLAGS and EIR_TX_POWER
without checking if that would fit.

Link: https://github.com/bluez/bluez/issues/1117#issuecomment-2958244066
Fixes: 01ce70b0a274 ("Bluetooth: eir: Move EIR/Adv Data functions to its own file")
Signed-off-by: Luiz Augusto von Dentz <[e-mail]>

net/bluetooth/eir.c

···
 	return ad_len;
 }
 
-u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr)
+u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr, u8 size)
 {
 	struct adv_info *adv = NULL;
 	u8 ad_len = 0, flags = 0;
···
 		/* If flags would still be empty, then there is no need to
 		 * include the "Flags" AD field".
 		 */
-		if (flags) {
+		if (flags && (ad_len + eir_precalc_len(1) <= size)) {
 			ptr[0] = 0x02;
 			ptr[1] = EIR_FLAGS;
 			ptr[2] = flags;
···
 		}
 
 		/* Provide Tx Power only if we can provide a valid value for it */
-		if (adv_tx_power != HCI_TX_POWER_INVALID) {
+		if (adv_tx_power != HCI_TX_POWER_INVALID &&
+		    (ad_len + eir_precalc_len(1) <= size)) {
 			ptr[0] = 0x02;
 			ptr[1] = EIR_TX_POWER;
 			ptr[2] = (u8)adv_tx_power;

net/bluetooth/eir.h

···
 
 void eir_create(struct hci_dev *hdev, u8 *data);
 
-u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr);
+u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr, u8 size);
 u8 eir_create_scan_rsp(struct hci_dev *hdev, u8 instance, u8 *ptr);
 u8 eir_create_per_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr);
 

net/bluetooth/hci_sync.c

···
 			return 0;
 	}
 
-	len = eir_create_adv_data(hdev, instance, pdu->data);
+	len = eir_create_adv_data(hdev, instance, pdu->data,
+				  HCI_MAX_EXT_AD_LENGTH);
 
 	pdu->length = len;
 	pdu->handle = adv ? adv->handle : instance;
···
 
 	memset(&cp, 0, sizeof(cp));
 
-	len = eir_create_adv_data(hdev, instance, cp.data);
+	len = eir_create_adv_data(hdev, instance, cp.data, sizeof(cp.data));
 
 	/* There's nothing to do if the data hasn't changed */
 	if (hdev->adv_data_len == len &&