[PATCH 4.9 67/86] usb: gadget: function: fix missing spinlock in f_uac1_legacy

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Zhang Qiang <qiang.zhang@xxxxxxxxxxxxx>

commit 8778eb0927ddcd3f431805c37b78fa56481aeed9 upstream.

Add a missing spinlock protection for play_queue, because
the play_queue may be destroyed when the "playback_work"
work func and "f_audio_out_ep_complete" callback func
operate this paly_queue at the same time.

Fixes: c6994e6f067cf ("USB: gadget: add USB Audio Gadget driver")
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Zhang Qiang <qiang.zhang@xxxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <balbi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/gadget/function/f_uac1.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/usb/gadget/function/f_uac1.c
+++ b/drivers/usb/gadget/function/f_uac1.c
@@ -336,7 +336,9 @@ static int f_audio_out_ep_complete(struc
 
 	/* Copy buffer is full, add it to the play_queue */
 	if (audio_buf_size - copy_buf->actual < req->actual) {
+		spin_lock_irq(&audio->lock);
 		list_add_tail(&copy_buf->list, &audio->play_queue);
+		spin_unlock_irq(&audio->lock);
 		schedule_work(&audio->playback_work);
 		copy_buf = f_audio_buffer_alloc(audio_buf_size);
 		if (IS_ERR(copy_buf))