[alsa-devel] Applied "ASoC: soc-core: fix init platform memory handling" to the asoc tree

[Mark Brown]

The patch

   ASoC: soc-core: fix init platform memory handling

has been applied to the asoc tree at

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

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 09ac6a817bd687e7f5dac00470262efdd72f9319 Mon Sep 17 00:00:00 2001
From: Curtis Malainey <cujomalainey at chromium.org>
Date: Thu, 10 Jan 2019 16:21:04 -0800
Subject: [PATCH] ASoC: soc-core: fix init platform memory handling

snd_soc_init_platform initializes pointers to snd_soc_dai_link which is
statically allocated and it does this by devm_kzalloc. In the event of
an EPROBE_DEFER the memory will be freed and the pointers are left
dangling. snd_soc_init_platform sees the dangling pointers and assumes
they are pointing to initialized memory and does not reallocate them on
the second probe attempt which results in a use after free bug since
devm has freed the memory from the first probe attempt.

Since the intention for snd_soc_dai_link->platform is that it can be set
statically by the machine driver we need to respect the pointer in the
event we did not set it but still catch dangling pointers. The solution
is to add a flag to track whether the pointer was dynamically allocated
or not.

Signed-off-by: Curtis Malainey <cujomalainey at chromium.org>
Signed-off-by: Mark Brown <broonie at kernel.org>
---
 include/sound/soc.h  |  6 ++++++
 sound/soc/soc-core.c | 11 ++++++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 8ec1de856ee7..e665f111b0d2 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -985,6 +985,12 @@ struct snd_soc_dai_link {
 	/* Do not create a PCM for this DAI link (Backend link) */
 	unsigned int ignore:1;
 
+	/*
+	 * This driver uses legacy platform naming. Set by the core, machine
+	 * drivers should not modify this value.
+	 */
+	unsigned int legacy_platform:1;
+
 	struct list_head list; /* DAI link list of the soc card */
 	struct snd_soc_dobj dobj; /* For topology */
 };
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 0934b36645b3..cdcc417c94ca 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -1034,17 +1034,18 @@ static int snd_soc_init_platform(struct snd_soc_card *card,
 	 * this function should be removed in the future
 	 */
 	/* convert Legacy platform link */
-	if (!platform) {
+	if (!platform || dai_link->legacy_platform) {
 		platform = devm_kzalloc(card->dev,
 				sizeof(struct snd_soc_dai_link_component),
 				GFP_KERNEL);
 		if (!platform)
 			return -ENOMEM;
 
-		dai_link->platform	= platform;
-		platform->name		= dai_link->platform_name;
-		platform->of_node	= dai_link->platform_of_node;
-		platform->dai_name	= NULL;
+		dai_link->platform	  = platform;
+		dai_link->legacy_platform = 1;
+		platform->name		  = dai_link->platform_name;
+		platform->of_node	  = dai_link->platform_of_node;
+		platform->dai_name	  = NULL;
 	}
 
 	/* if there's no platform we match on the empty platform */
-- 
2.20.1