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

[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@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@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Libin Yang <libin.yang@intel.com>
Reviewed-by: Bard Liao <bard.liao@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

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

[Mark Brown]

On Wed, 13 Jan 2021 17:07:15 +0200, Kai Vehmanen wrote:
> 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.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[1/1] ASoC: SOF: Intel: fix page fault at probe if i915 init fails
      commit: 9c25af250214e45f6d1c21ff6239a1ffeeedf20e

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark