[alsa-devel] Applied "ASoC: core: move DAI pre-links initiation to snd_soc_instantiate_card" to the asoc tree

[Mark Brown]

The patch

   ASoC: core: move DAI pre-links initiation to snd_soc_instantiate_card

has been applied to the asoc tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-5.2

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

>From 70fc53734e71ce51f46dfcfd1a1c319e1cfe080c Mon Sep 17 00:00:00 2001
From: Tzung-Bi Shih <tzungbi at google.com>
Date: Tue, 4 Jun 2019 11:31:02 +0800
Subject: [PATCH] ASoC: core: move DAI pre-links initiation to
 snd_soc_instantiate_card

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 at google.com>
Signed-off-by: Mark Brown <broonie at 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 46042d41b79b..3fecd957995e 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -2072,6 +2072,16 @@ 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;
@@ -2796,26 +2806,9 @@ 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