[PATCH v3 01/26] ALSA: compress: pin card module while stream is open

[Peter Ujfalusi <peter.ujfalusi@linux.intel.com>]

Take a module reference in snd_compr_open() and release it in
snd_compr_free(). This pins the card driver module for the
lifetime of an open compress stream and prevents card removal
while the stream file is still in use.

Adjust the open() cleanup paths to drop the added module
reference only when it was acquired, and keep release ordering
safe by dropping the module reference before freeing stream
data.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Liam Girdwood <liam.r.girdwood@intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
---
 sound/core/compress_offload.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index 7c397b1c9231..ba6cdfe64246 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -75,11 +75,11 @@ static inline void snd_compr_task_free_all(struct snd_compr_stream *stream) { }
 static int snd_compr_open(struct inode *inode, struct file *f)
 {
 	struct snd_compr *compr;
-	struct snd_compr_file *data;
-	struct snd_compr_runtime *runtime;
+	struct snd_compr_file *data = NULL;
+	struct snd_compr_runtime *runtime = NULL;
 	enum snd_compr_direction dirn;
 	int maj = imajor(inode);
-	int ret;
+	int ret = 0;
 
 	if ((f->f_flags & O_ACCMODE) == O_WRONLY)
 		dirn = SND_COMPRESS_PLAYBACK;
@@ -101,16 +101,21 @@ static int snd_compr_open(struct inode *inode, struct file *f)
 		return -ENODEV;
 	}
 
+	if (!try_module_get(compr->card->module)) {
+		snd_card_unref(compr->card);
+		return -EFAULT;
+	}
+
 	if (dirn != compr->direction) {
 		pr_err("this device doesn't support this direction\n");
-		snd_card_unref(compr->card);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto __error;
 	}
 
 	data = kzalloc_obj(*data);
 	if (!data) {
-		snd_card_unref(compr->card);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto __error;
 	}
 
 	INIT_DELAYED_WORK(&data->stream.error_work, error_delayed_work);
@@ -121,9 +126,8 @@ static int snd_compr_open(struct inode *inode, struct file *f)
 	data->stream.device = compr;
 	runtime = kzalloc_obj(*runtime);
 	if (!runtime) {
-		kfree(data);
-		snd_card_unref(compr->card);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto __error;
 	}
 	runtime->state = SNDRV_PCM_STATE_OPEN;
 	init_waitqueue_head(&runtime->sleep);
@@ -134,9 +138,12 @@ static int snd_compr_open(struct inode *inode, struct file *f)
 	f->private_data = (void *)data;
 	scoped_guard(mutex, &compr->lock)
 		ret = compr->ops->open(&data->stream);
+
+__error:
 	if (ret) {
 		kfree(runtime);
 		kfree(data);
+		module_put(compr->card->module);
 	}
 	snd_card_unref(compr->card);
 	return ret;
@@ -164,6 +171,7 @@ static int snd_compr_free(struct inode *inode, struct file *f)
 	data->stream.ops->free(&data->stream);
 	if (!data->stream.runtime->dma_buffer_p)
 		kfree(data->stream.runtime->buffer);
+	module_put(data->stream.device->card->module);
 	kfree(data->stream.runtime);
 	kfree(data);
 	return 0;
-- 
2.55.0