Bluetooth: Fix slab-out-of-bounds read in hci_extended_inquiry_result_evt()

commit 51c19bf upstream.

Check upon `num_rsp` is insufficient. A malformed event packet with a
large `num_rsp` number makes hci_extended_inquiry_result_evt() go out
of bounds. Fix it.

This patch fixes the following syzbot bug:

    https://syzkaller.appspot.com/bug?id=4bf11aa05c4ca51ce0df86e500fce486552dc8d2

Reported-by: [email protected]
Cc: [email protected]
Signed-off-by: Peilin Ye <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Marcel Holtmann <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: peilin-ye

net/bluetooth/hci_event.c

@@ -3826,7 +3826,7 @@ static void hci_extended_inquiry_result_evt(struct hci_dev *hdev,
 
 	BT_DBG("%s num_rsp %d", hdev->name, num_rsp);
 
-	if (!num_rsp)
+	if (!num_rsp || skb->len < num_rsp * sizeof(*info) + 1)
 		return;
 
 	if (hci_dev_test_flag(hdev, HCI_PERIODIC_INQ))