ASoC: SOF: core: fix error handling with the probe workqueue

In some configurations, it's a requirement to split the probe in two,
with a second part handled in a workqueue (e.g. for HDMI support
which depends on the DRM modules).

SOF already handles these configurations but the error flow is
incorrect. When an error occurs in the workqueue, the probe has
technically already completed. If we release the resources on errors,
this generates kernel oops/use-after-free when the resources are
released a second time on module removal.

GitHub issue: https://github.com/thesofproject/linux/issues/945
Fixes: c16211d6 ("ASoC: SOF: Add Sound Open Firmware driver core")
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/core.c

@@ -393,6 +393,7 @@ static int sof_probe_continue(struct snd_sof_dev *sdev)
 
 	return 0;
 
+#if !IS_ENABLED(CONFIG_SND_SOC_SOF_PROBE_WORK_QUEUE)
 fw_run_err:
 	snd_sof_fw_unload(sdev);
 fw_load_err:
@@ -401,6 +402,21 @@ static int sof_probe_continue(struct snd_sof_dev *sdev)
 	snd_sof_free_debug(sdev);
 dbg_err:
 	snd_sof_remove(sdev);
+#else
+
+	/*
+	 * when the probe_continue is handled in a work queue, the
+	 * probe does not fail so we don't release resources here.
+	 * They will be released with an explicit call to
+	 * snd_sof_device_remove() when the PCI/ACPI device is removed
+	 */
+
+fw_run_err:
+fw_load_err:
+ipc_err:
+dbg_err:
+
+#endif
 
 	return ret;
 }