[PATCH] Bluetooth: hci_event: fix out-of-bounds read in LE PA report reassembly

hci_le_per_adv_report_evt() is dispatched with a minimum length of
sizeof(struct hci_ev_le_per_adv_report), which only covers the fixed
part of the event and not the trailing data[] array:

	struct hci_ev_le_per_adv_report {
		__le16   sync_handle;
		__u8     tx_power;
		__u8     rssi;
		__u8     cte_type;
		__u8     data_status;
		__u8     length;
		__u8     data[];
	} __packed;

The handler notifies the ISO layer via hci_proto_connect_ind(), which
reaches iso_connect_ind(). That function retrieves the stored event with
hci_recv_event_data() and, while reassembling the periodic advertising
data, does:

	memcpy(hcon->le_per_adv_data + hcon->le_per_adv_data_offset,
	       ev->data, ev->length);

ev->length is taken directly from the event and is never validated
against the amount of data the event actually carries.  A controller
that reports a length larger than the received event therefore causes
the memcpy() to read past the end of the event buffer.  The leaked bytes
are stored in hcon->le_per_adv_data and can subsequently be read back
from user space via getsockopt(BT_ISO_BASE).

Validate that the event contains ev->length data bytes before it is
consumed, mirroring the check already performed by
hci_le_ext_adv_report_evt() and hci_le_adv_report_evt().

Signed-off-by: Laxman Acharya <[email protected]>
---
 net/bluetooth/hci_event.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 741d658e9..727545e0c 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -6604,6 +6604,13 @@ static void hci_le_per_adv_report_evt(struct hci_dev *hdev, void *data,
 
 	bt_dev_dbg(hdev, "sync_handle 0x%4.4x", le16_to_cpu(ev->sync_handle));
 
+	/* The reassembly in iso_connect_ind() copies ev->length bytes from the
+	 * stored event, so make sure the event actually carries that many data
+	 * bytes before it is consumed.
+	 */
+	if (!hci_le_ev_skb_pull(hdev, skb, HCI_EV_LE_PER_ADV_REPORT, ev->length))
+		return;
+
 	hci_dev_lock(hdev);
 
 	mask |= hci_proto_connect_ind(hdev, BDADDR_ANY, PA_LINK, &flags);
-- 
2.51.2