CVE-2026-90254

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: hci_sync: free the advertising instance on the failure and cancel paths

adv_timeout_expire() hands a kmalloc()ed instance byte to
hci_cmd_sync_queue() with a NULL destroy callback, and only
adv_timeout_expire_sync() frees it. That leaks on two paths:

 - the return value is not checked, and hci_cmd_sync_queue() does not
   take ownership when it fails (-ENETDOWN, -ENODEV, -ENOMEM);

 - a cancelled entry is not released, as _hci_cmd_sync_cancel_entry()
   does not free entry->data when there is no destroy callback.
   hci_cmd_sync_clear() cancels every pending entry when the controller
   is unregistered.

Free the buffer from a destroy callback, and in the caller when the entry
could not be queued at all.