--- linux-4.9.37/drivers/usb/gadget/function/u_uac1.c	2017-07-12 16:42:41.000000000 +0300
+++ linux-4.9.y/drivers/usb/gadget/function/u_uac1.c	2021-06-07 13:01:34.000000000 +0300
@@ -157,7 +157,6 @@
 	struct gaudio_snd_dev	*snd = &card->playback;
 	struct snd_pcm_substream *substream = snd->substream;
 	struct snd_pcm_runtime *runtime = substream->runtime;
-	mm_segment_t old_fs;
 	ssize_t result;
 	snd_pcm_sframes_t frames;
 
@@ -174,15 +173,11 @@
 	}
 
 	frames = bytes_to_frames(runtime, count);
-	old_fs = get_fs();
-	set_fs(KERNEL_DS);
-	result = snd_pcm_lib_write(snd->substream, (void __user *)buf, frames);
+	result = snd_pcm_kernel_write(snd->substream, buf, frames);
 	if (result != frames) {
 		ERROR(card, "Playback error: %d\n", (int)result);
-		set_fs(old_fs);
 		goto try_again;
 	}
-	set_fs(old_fs);
 
 	return 0;
 }