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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, Tzung-Bi Shih <tzungbi@google.com>,
        Mark Brown <broonie@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.1 35/96] ASoC: core: move DAI pre-links initiation to snd_soc_instantiate_card
Date:   Mon,  8 Jul 2019 17:13:07 +0200
Message-Id: <20190708150528.462560432@linuxfoundation.org>
In-Reply-To: <20190708150526.234572443@linuxfoundation.org>
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[ Upstream commit 70fc53734e71ce51f46dfcfd1a1c319e1cfe080c ]

Kernel crashes when an ASoC component rebinding.

The dai_link->platforms has been reset to NULL by soc_cleanup_platform()
in soc_cleanup_card_resources() when un-registering component.  However,
it has no chance to re-allocate the dai_link->platforms when registering
the component again.

Move the DAI pre-links initiation from snd_soc_register_card() to
snd_soc_instantiate_card() to make sure all DAI pre-links get initiated
when component rebinding.

As an example, by using the following commands:
- echo -n max98357a > /sys/bus/platform/drivers/max98357a/unbind
- echo -n max98357a > /sys/bus/platform/drivers/max98357a/bind

Got the error message:
"Unable to handle kernel NULL pointer dereference at virtual address".

The call trace:
snd_soc_is_matching_component+0x30/0x6c
soc_bind_dai_link+0x16c/0x240
snd_soc_bind_card+0x1e4/0xb10
snd_soc_add_component+0x270/0x300
snd_soc_register_component+0x54/0x6c

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 sound/soc/soc-core.c | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index a4668a788ed5..9df3bdeb5c47 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -2069,6 +2069,16 @@ static int snd_soc_instantiate_card(struct snd_soc_card *card)
 	int ret, i, order;
 
 	mutex_lock(&client_mutex);
+	for_each_card_prelinks(card, i, dai_link) {
+		ret = soc_init_dai_link(card, dai_link);
+		if (ret) {
+			soc_cleanup_platform(card);
+			dev_err(card->dev, "ASoC: failed to init link %s: %d\n",
+				dai_link->name, ret);
+			mutex_unlock(&client_mutex);
+			return ret;
+		}
+	}
 	mutex_lock_nested(&card->mutex, SND_SOC_CARD_CLASS_INIT);
 
 	card->dapm.bias_level = SND_SOC_BIAS_OFF;
@@ -2793,26 +2803,9 @@ static int snd_soc_bind_card(struct snd_soc_card *card)
  */
 int snd_soc_register_card(struct snd_soc_card *card)
 {
-	int i, ret;
-	struct snd_soc_dai_link *link;
-
 	if (!card->name || !card->dev)
 		return -EINVAL;
 
-	mutex_lock(&client_mutex);
-	for_each_card_prelinks(card, i, link) {
-
-		ret = soc_init_dai_link(card, link);
-		if (ret) {
-			soc_cleanup_platform(card);
-			dev_err(card->dev, "ASoC: failed to init link %s\n",
-				link->name);
-			mutex_unlock(&client_mutex);
-			return ret;
-		}
-	}
-	mutex_unlock(&client_mutex);
-
 	dev_set_drvdata(card->dev, card);
 
 	snd_soc_initialize_card_lists(card);
-- 
2.20.1