4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Wu <redacted>

commit ab58d8cc870ef3f0771c197700441936898d1f1d upstream.

register_vga_switcheroo() sets the PM ops from the hda structure which
is freed later in azx_free. Make sure that these ops are cleared.

Caught by KASAN, initially noticed due to a general protection fault.

Fixes: 246efa4a072f ("snd/hda: add runtime suspend/resume on optimus support (v4)")
Signed-off-by: Peter Wu <redacted>
Signed-off-by: Takashi Iwai <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/pci/hda/hda_intel.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c

@@ -1256,8 +1256,10 @@ static int azx_free(struct azx *chip)
 	if (use_vga_switcheroo(hda)) {
 		if (chip->disabled && hda->probe_continued)
 			snd_hda_unlock_devices(&chip->bus);
-		if (hda->vga_switcheroo_registered)
+		if (hda->vga_switcheroo_registered) {
 			vga_switcheroo_unregister_client(chip->pci);
+			vga_switcheroo_fini_domain_pm_ops(chip->card->dev);
+		}
 	}
 
 	if (bus->chip_init) {