3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Clemens Ladisch <clemens@ladisch.de>

commit 5cd5d7c44990658df6ab49f6253c39617c53b03d upstream.

The array of sample rates is reallocated every time when opening
the PCM device, but was freed only once when unplugging the device.

Reported-by: "Alexander E. Patrakov" <redacted>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/usb/pcm.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c

@@ -699,6 +699,9 @@ static int snd_usb_pcm_check_knot(struct
 	int count = 0, needs_knot = 0;
 	int err;
 
+	kfree(subs->rate_list.list);
+	subs->rate_list.list = NULL;
+
 	list_for_each_entry(fp, &subs->fmt_list, list) {
 		if (fp->rates & SNDRV_PCM_RATE_CONTINUOUS)
 			return 0;