[alsa-devel] Applied "ASoC: dapm: Add a dummy snd_pcm_runtime to avoid NULL pointer access" to the asoc tree

[Mark Brown]

The patch

   ASoC: dapm: Add a dummy snd_pcm_runtime to avoid NULL pointer access

has been applied to the asoc tree at

   git://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 8053f21675b073b379cbca258ee4a3f3850dfa94 Mon Sep 17 00:00:00 2001
From: Nicolin Chen <nicoleotsuka at gmail.com>
Date: Tue, 26 Jul 2016 14:55:51 -0700
Subject: [PATCH] ASoC: dapm: Add a dummy snd_pcm_runtime to avoid NULL pointer
 access

The SND_SOC_DAPM_PRE_PMU case would call startup()/hw_params() that
might access substream->runtime through other functions.

For example:

Unable to handle kernel NULL pointer dereference at virtual address
[....]
PC is at snd_pcm_hw_rule_add+0x24/0x1b0
LR is at snd_pcm_hw_constraint_list+0x20/0x28
[....]
Process arecord (pid: 424, stack limit = 0xffffffc1ecaf0020)
Call trace:
[<ffffffc00086be68>] snd_pcm_hw_rule_add+0x24/0x1b0
[<ffffffc00086c014>] snd_pcm_hw_constraint_list+0x20/0x28
[<ffffffc0008b47a4>] cs53l30_pcm_startup+0x24/0x30
[<ffffffc0008a6260>] snd_soc_dai_link_event+0x290/0x354
[<ffffffc0008a7528>] dapm_seq_check_event.isra.31+0x134/0x2c8
[<ffffffc0008a7768>] dapm_seq_run_coalesced+0x94/0x1c8
[<ffffffc0008a7940>] dapm_seq_run+0xa4/0x404
[<ffffffc0008a8bac>] dapm_power_widgets+0x524/0x984
[<ffffffc0008ab1c4>] snd_soc_dapm_stream_event+0x8c/0xa8
[<ffffffc0008ac7f4>] soc_pcm_prepare+0x10c/0x1ec
[<ffffffc000865b9c>] snd_pcm_do_prepare+0x1c/0x38
[<ffffffc000865600>] snd_pcm_action_single+0x40/0x88
[<ffffffc0008656b8>] snd_pcm_action_nonatomic+0x70/0x90
[<ffffffc000868d28>] snd_pcm_common_ioctl1+0xb6c/0xdd8
[<ffffffc000869508>] snd_pcm_capture_ioctl1+0x200/0x334
[<ffffffc00086a084>] snd_pcm_ioctl_compat+0x648/0x95c
[<ffffffc0001ff4b4>] compat_SyS_ioctl+0xac/0xfc4
[<ffffffc000084cf0>] el0_svc_naked+0x24/0x28
---[ end trace 0dc4f99c2759c35c ]---

So this patch adds a dummy runtime for the original dummy substream
to merely avoid the NULL pointer access.

Signed-off-by: Nicolin Chen <nicoleotsuka at gmail.com>
Signed-off-by: Mark Brown <broonie at kernel.org>
---
 sound/soc/soc-dapm.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index 8698c26773b3..d908ff8f9755 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -3493,6 +3493,7 @@ static int snd_soc_dai_link_event(struct snd_soc_dapm_widget *w,
 	const struct snd_soc_pcm_stream *config = w->params + w->params_select;
 	struct snd_pcm_substream substream;
 	struct snd_pcm_hw_params *params = NULL;
+	struct snd_pcm_runtime *runtime = NULL;
 	u64 fmt;
 	int ret;
 
@@ -3541,6 +3542,14 @@ static int snd_soc_dai_link_event(struct snd_soc_dapm_widget *w,
 
 	memset(&substream, 0, sizeof(substream));
 
+	/* Allocate a dummy snd_pcm_runtime for startup() and other ops() */
+	runtime = kzalloc(sizeof(*runtime), GFP_KERNEL);
+	if (!runtime) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	substream.runtime = runtime;
+
 	switch (event) {
 	case SND_SOC_DAPM_PRE_PMU:
 		substream.stream = SNDRV_PCM_STREAM_CAPTURE;
@@ -3606,6 +3615,7 @@ static int snd_soc_dai_link_event(struct snd_soc_dapm_widget *w,
 	}
 
 out:
+	kfree(runtime);
 	kfree(params);
 	return ret;
 }
-- 
2.8.1