CVE-2024-38388: Missing Release of Memory after Effective Lifetime

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

ALSA: hda/cs_dsp_ctl: Use private_free for control cleanup

Use the control private_free callback to free the associated data block. This ensures that the memory won't leak, whatever way the control gets destroyed.

The original implementation didn't actually remove the ALSA controls in hda_cs_dsp_control_remove(). It only freed the internal tracking structure. This meant it was possible to remove/unload the amp driver while leaving its ALSA controls still present in the soundcard. Obviously attempting to access them could cause segfaults or at least dereferencing stale pointers.