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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Takashi Iwai <tiwai@suse.de>
Subject: [PATCH 4.4 084/143] ALSA: hda - Serialize codec registrations
Date:   Mon, 18 Feb 2019 14:43:32 +0100
Message-Id: <20190218133532.140094760@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Takashi Iwai <tiwai@suse.de>

commit 305a0ade180981686eec1f92aa6252a7c6ebb1cf upstream.

In the current code, the codec registration may happen both at the
codec bind time and the end of the controller probe time.  In a rare
occasion, they race with each other, leading to Oops due to the still
uninitialized card device.

This patch introduces a simple flag to prevent the codec registration
at the codec bind time as long as the controller probe is going on.
The controller probe invokes snd_card_register() that does the whole
registration task, and we don't need to register each piece
beforehand.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/pci/hda/hda_bind.c  |    3 ++-
 sound/pci/hda/hda_codec.h |    1 +
 sound/pci/hda/hda_intel.c |    2 ++
 3 files changed, 5 insertions(+), 1 deletion(-)

--- a/sound/pci/hda/hda_bind.c
+++ b/sound/pci/hda/hda_bind.c
@@ -109,7 +109,8 @@ static int hda_codec_driver_probe(struct
 	err = snd_hda_codec_build_controls(codec);
 	if (err < 0)
 		goto error_module;
-	if (codec->card->registered) {
+	/* only register after the bus probe finished; otherwise it's racy */
+	if (!codec->bus->bus_probing && codec->card->registered) {
 		err = snd_card_register(codec->card);
 		if (err < 0)
 			goto error_module;
--- a/sound/pci/hda/hda_codec.h
+++ b/sound/pci/hda/hda_codec.h
@@ -68,6 +68,7 @@ struct hda_bus {
 	unsigned int response_reset:1;	/* controller was reset */
 	unsigned int in_reset:1;	/* during reset operation */
 	unsigned int no_response_fallback:1; /* don't fallback at RIRB error */
+	unsigned int bus_probing :1;	/* during probing process */
 
 	int primary_dig_out_type;	/* primary digital out PCM type */
 	unsigned int mixer_assigned;	/* codec addr for mixer name */
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -2100,6 +2100,7 @@ static int azx_probe_continue(struct azx
 	int val;
 	int err;
 
+	to_hda_bus(bus)->bus_probing = 1;
 	hda->probe_continued = 1;
 
 	/* Request display power well for the HDA controller or codec. For
@@ -2200,6 +2201,7 @@ i915_power_fail:
 	if (err < 0)
 		hda->init_failed = 1;
 	complete_all(&hda->probe_wait);
+	to_hda_bus(bus)->bus_probing = 0;
 	return err;
 }