[PATCH] ASoC: SOF: Intel: fix page fault at probe if i915 init fails

[Kai Vehmanen]

The earlier commit to fix runtime PM in case i915 init fails,
introduces a possibility to hit a page fault.

snd_hdac_ext_bus_device_exit() is designed to be called from
dev.release(). Calling it outside device reference counting, is
not safe and may lead to calling the device_exit() function
twice. Additionally, as part of ext_bus_device_init(), the device
is also registered with snd_hdac_device_register(). Thus before
calling device_exit(), the device must be removed from device
hierarchy first.

Fix the issue by rolling back init actions by calling
hdac_device_unregister() and then releasing device with put_device().
This matches with existing code in hdac-ext module.

To complete the fix, add handling for the case where
hda_codec_load_module() returns -ENODEV, and clean up the hdac_ext
resources also in this case.

In future work, hdac-ext interface should be extended to allow clients
more flexibility to handle the life-cycle of individual devices, beyond
just the current snd_hdac_ext_bus_device_remove(), which removes all
devices.

BugLink: https://github.com/thesofproject/linux/issues/2646
Reported-by: Jaroslav Kysela <perex at perex.cz>
Fixes: 6c63c954e1c5 ("ASoC: SOF: fix a runtime pm issue in SOF when HDMI codec doesn't work")
Signed-off-by: Kai Vehmanen <kai.vehmanen at linux.intel.com>
Reviewed-by: Rander Wang <rander.wang at intel.com>
Reviewed-by: Libin Yang <libin.yang at intel.com>
Reviewed-by: Bard Liao <bard.liao at intel.com>
---
 sound/soc/sof/intel/hda-codec.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/sound/soc/sof/intel/hda-codec.c b/sound/soc/sof/intel/hda-codec.c
index 6875fa570c2c..8b0ddc4b8227 100644
--- a/sound/soc/sof/intel/hda-codec.c
+++ b/sound/soc/sof/intel/hda-codec.c
@@ -156,7 +156,8 @@ static int hda_codec_probe(struct snd_sof_dev *sdev, int address,
 		if (!hdev->bus->audio_component) {
 			dev_dbg(sdev->dev,
 				"iDisp hw present but no driver\n");
-			goto error;
+			ret = -ENOENT;
+			goto out;
 		}
 		hda_priv->need_display_power = true;
 	}
@@ -173,24 +174,23 @@ static int hda_codec_probe(struct snd_sof_dev *sdev, int address,
 		 * other return codes without modification
 		 */
 		if (ret == 0)
-			goto error;
+			ret = -ENOENT;
 	}
 
-	return ret;
-
-error:
-	snd_hdac_ext_bus_device_exit(hdev);
-	return -ENOENT;
-
+out:
+	if (ret < 0) {
+		snd_hdac_device_unregister(hdev);
+		put_device(&hdev->dev);
+	}
 #else
 	hdev = devm_kzalloc(sdev->dev, sizeof(*hdev), GFP_KERNEL);
 	if (!hdev)
 		return -ENOMEM;
 
 	ret = snd_hdac_ext_bus_device_init(&hbus->core, address, hdev, HDA_DEV_ASOC);
+#endif
 
 	return ret;
-#endif
 }
 
 /* Codec initialization */
-- 
2.29.2