ASoC: msm: qdsp6v2: make audio debugfs read and release exclusive

A thread can read audio debugfs entry while another closes the
device. Protect these operations with a mutex and before read
check audio data to be a valid pointer.

Change-Id: If29a308c1a8329d7befd047d41abe5f6ab626199
Signed-off-by: Divya Ojha <dojha@codeaurora.org>

1 files changed, 36 insertions, 22 deletions

diff --git a/drivers/misc/qcom/qdsp6v2/audio_utils_aio.c b/drivers/misc/qcom/qdsp6v2/audio_utils_aio.c
index 5419bd1655c1..b292ea70fb40 100644
--- a/drivers/misc/qcom/qdsp6v2/audio_utils_aio.c
+++ b/drivers/misc/qcom/qdsp6v2/audio_utils_aio.c
@@ -26,11 +26,14 @@
 #include <linux/debugfs.h>
 #include <linux/msm_audio_ion.h>
 #include <linux/compat.h>
+#include <linux/mutex.h>
 #include "audio_utils_aio.h"
 #ifdef CONFIG_USE_DEV_CTRL_VOLUME
 #include <linux/qdsp6v2/audio_dev_ctl.h>
 #endif /*CONFIG_USE_DEV_CTRL_VOLUME*/
+static DEFINE_MUTEX(lock);
 #ifdef CONFIG_DEBUG_FS
+
 int audio_aio_debug_open(struct inode *inode, struct file *file)
 {
 	file->private_data = inode->i_private;
@@ -43,29 +46,37 @@ ssize_t audio_aio_debug_read(struct file *file, char __user *buf,
 	const int debug_bufmax = 4096;
 	static char buffer[4096];
 	int n = 0;
-	struct q6audio_aio *audio = file->private_data;
+	struct q6audio_aio *audio;
 
-	mutex_lock(&audio->lock);
-	n = scnprintf(buffer, debug_bufmax, "opened %d\n", audio->opened);
-	n += scnprintf(buffer + n, debug_bufmax - n,
-			"enabled %d\n", audio->enabled);
-	n += scnprintf(buffer + n, debug_bufmax - n,
-			"stopped %d\n", audio->stopped);
-	n += scnprintf(buffer + n, debug_bufmax - n,
-			"feedback %d\n", audio->feedback);
-	mutex_unlock(&audio->lock);
-	/* Following variables are only useful for debugging when
-	 * when playback halts unexpectedly. Thus, no mutual exclusion
-	 * enforced
-	 */
-	n += scnprintf(buffer + n, debug_bufmax - n,
-			"wflush %d\n", audio->wflush);
-	n += scnprintf(buffer + n, debug_bufmax - n,
-			"rflush %d\n", audio->rflush);
-	n += scnprintf(buffer + n, debug_bufmax - n,
-			"inqueue empty %d\n", list_empty(&audio->in_queue));
-	n += scnprintf(buffer + n, debug_bufmax - n,
-			"outqueue empty %d\n", list_empty(&audio->out_queue));
+	mutex_lock(&lock);
+	if (file->private_data != NULL) {
+		audio = file->private_data;
+		mutex_lock(&audio->lock);
+		n = scnprintf(buffer, debug_bufmax, "opened %d\n",
+				audio->opened);
+		n += scnprintf(buffer + n, debug_bufmax - n,
+				"enabled %d\n", audio->enabled);
+		n += scnprintf(buffer + n, debug_bufmax - n,
+				"stopped %d\n", audio->stopped);
+		n += scnprintf(buffer + n, debug_bufmax - n,
+				"feedback %d\n", audio->feedback);
+		mutex_unlock(&audio->lock);
+		/* Following variables are only useful for debugging when
+		 * when playback halts unexpectedly. Thus, no mutual exclusion
+		 * enforced
+		 */
+		n += scnprintf(buffer + n, debug_bufmax - n,
+				"wflush %d\n", audio->wflush);
+		n += scnprintf(buffer + n, debug_bufmax - n,
+				"rflush %d\n", audio->rflush);
+		n += scnprintf(buffer + n, debug_bufmax - n,
+				"inqueue empty %d\n",
+				list_empty(&audio->in_queue));
+		n += scnprintf(buffer + n, debug_bufmax - n,
+				"outqueue empty %d\n",
+				list_empty(&audio->out_queue));
+	}
+	mutex_unlock(&lock);
 	buffer[n] = 0;
 	return simple_read_from_buffer(buf, count, ppos, buffer, n);
 }
@@ -573,6 +584,7 @@ int audio_aio_release(struct inode *inode, struct file *file)
 {
 	struct q6audio_aio *audio = file->private_data;
 	pr_debug("%s[%pK]\n", __func__, audio);
+	mutex_lock(&lock);
 	mutex_lock(&audio->lock);
 	mutex_lock(&audio->read_lock);
 	mutex_lock(&audio->write_lock);
@@ -616,6 +628,8 @@ int audio_aio_release(struct inode *inode, struct file *file)
 #endif
 	kfree(audio->codec_cfg);
 	kfree(audio);
+	file->private_data = NULL;
+	mutex_unlock(&lock);
 	return 0;
 }