usb: gadget: Fix synchronization issue between f_audio_source

Race is happening when both audio_pcm_close() and audio_send()
executes in parallel.
When the PCM session is closed, the substream attribute of the
audio_dev structure is set to NULL in audio_pcm_close().
As there is no synchronization protection for the audio_dev subtream
attributes in audio_send(), it is causing NULL pointer dereference.
Hence fixing the issue by adding proper synchronization protection
for the audio_dev subtream attributes in audio_send().

CRs-Fixed: 613498
Change-Id: Id9ab0d4e347b8bb2f551f9033829e541bdcaf0e8
Signed-off-by: ChandanaKishori Chiluveru <cchilu@codeaurora.org>
Signed-off-by: Tarun Gupta <tarung@codeaurora.org>

1 files changed, 24 insertions, 3 deletions

diff --git a/drivers/usb/gadget/function/f_audio_source.c b/drivers/usb/gadget/function/f_audio_source.c
index 51ab794ef6f9..ab7441fcf66f 100644
--- a/drivers/usb/gadget/function/f_audio_source.c
+++ b/drivers/usb/gadget/function/f_audio_source.c
@@ -369,15 +369,22 @@ static void audio_send(struct audio_dev *audio)
 	s64 msecs;
 	s64 frames;
 	ktime_t now;
+	unsigned long flags;
 
+	spin_lock_irqsave(&audio->lock, flags);
 	/* audio->substream will be null if we have been closed */
-	if (!audio->substream)
+	if (!audio->substream) {
+		spin_unlock_irqrestore(&audio->lock, flags);
 		return;
+	}
 	/* audio->buffer_pos will be null if we have been stopped */
-	if (!audio->buffer_pos)
+	if (!audio->buffer_pos) {
+		spin_unlock_irqrestore(&audio->lock, flags);
 		return;
+	}
 
 	runtime = audio->substream->runtime;
+	spin_unlock_irqrestore(&audio->lock, flags);
 
 	/* compute number of frames to send */
 	now = ktime_get();
@@ -400,8 +407,21 @@ static void audio_send(struct audio_dev *audio)
 
 	while (frames > 0) {
 		req = audio_req_get(audio);
-		if (!req)
+		spin_lock_irqsave(&audio->lock, flags);
+		/* audio->substream will be null if we have been closed */
+		if (!audio->substream) {
+			spin_unlock_irqrestore(&audio->lock, flags);
+			return;
+		}
+		/* audio->buffer_pos will be null if we have been stopped */
+		if (!audio->buffer_pos) {
+			spin_unlock_irqrestore(&audio->lock, flags);
+			return;
+		}
+		if (!req) {
+			spin_unlock_irqrestore(&audio->lock, flags);
 			break;
+		}
 
 		length = frames_to_bytes(runtime, frames);
 		if (length > IN_EP_MAX_PACKET_SIZE)
@@ -427,6 +447,7 @@ static void audio_send(struct audio_dev *audio)
 		}
 
 		req->length = length;
+		spin_unlock_irqrestore(&audio->lock, flags);
 		ret = usb_ep_queue(audio->in_ep, req, GFP_ATOMIC);
 		if (ret < 0) {
 			pr_err("usb_ep_queue failed ret: %d\n", ret);