linux-kernel - [PATCH AUTOSEL 5.10 03/13] ALSA: hda: Do not unset preset when cleaning up codec

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Date:   Thu,  9 Feb 2023 06:18:21 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Cezary Rojewski <cezary.rojewski@...el.com>,
        Takashi Iwai <tiwai@...e.com>, Takashi Iwai <tiwai@...e.de>,
        Sasha Levin <sashal@...nel.org>, perex@...ex.cz,
        pierre-louis.bossart@...ux.intel.com, kai.vehmanen@...ux.intel.com,
        mkumard@...dia.com, alsa-devel@...a-project.org
Subject: [PATCH AUTOSEL 5.10 03/13] ALSA: hda: Do not unset preset when cleaning up codec

From: Cezary Rojewski <cezary.rojewski@...el.com>

[ Upstream commit 87978e6ad45a16835cc58234451111091be3c59a ]

Several functions that take part in codec's initialization and removal
are re-used by ASoC codec drivers implementations. Drivers mimic the
behavior of hda_codec_driver_probe/remove() found in
sound/pci/hda/hda_bind.c with their component->probe/remove() instead.

One of the reasons for that is the expectation of
snd_hda_codec_device_new() to receive a valid pointer to an instance of
struct snd_card. This expectation can be met only once sound card
components probing commences.

As ASoC sound card may be unbound without codec device being actually
removed from the system, unsetting ->preset in
snd_hda_codec_cleanup_for_unbind() interferes with module unload -> load
scenario causing null-ptr-deref. Preset is assigned only once, during
device/driver matching whereas ASoC codec driver's module reloading may
occur several times throughout the lifetime of an audio stack.

Suggested-by: Takashi Iwai <tiwai@...e.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@...el.com>
Link: https://lore.kernel.org/r/20230119143235.1159814-1-cezary.rojewski@intel.com
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/pci/hda/hda_bind.c  | 2 ++
 sound/pci/hda/hda_codec.c | 1 -
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/sound/pci/hda/hda_bind.c b/sound/pci/hda/hda_bind.c
index 4efbcc41fdfb7..0a83afa5f373c 100644
--- a/sound/pci/hda/hda_bind.c
+++ b/sound/pci/hda/hda_bind.c
@@ -143,6 +143,7 @@ static int hda_codec_driver_probe(struct device *dev)
 
  error:
 	snd_hda_codec_cleanup_for_unbind(codec);
+	codec->preset = NULL;
 	return err;
 }
 
@@ -159,6 +160,7 @@ static int hda_codec_driver_remove(struct device *dev)
 	if (codec->patch_ops.free)
 		codec->patch_ops.free(codec);
 	snd_hda_codec_cleanup_for_unbind(codec);
+	codec->preset = NULL;
 	module_put(dev->driver->owner);
 	return 0;
 }
diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
index 39281106477eb..fc4a64a83ff2f 100644
--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -784,7 +784,6 @@ void snd_hda_codec_cleanup_for_unbind(struct hda_codec *codec)
 	snd_array_free(&codec->cvt_setups);
 	snd_array_free(&codec->spdif_out);
 	snd_array_free(&codec->verbs);
-	codec->preset = NULL;
 	codec->follower_dig_outs = NULL;
 	codec->spdif_status_reset = 0;
 	snd_array_free(&codec->mixers);
-- 
2.39.0