n_gsm: memory leak in uplink error path

Uplink (TX) network data will go through gsm_dlci_data_output_framed
there is a bug where if memory allocation fails, the skb which
has already been pulled off the list will be lost.

In addition TX skbs were being processed in LIFO order

Fixed the memory leak, and changed to FIFO order processing

Signed-off-by: Russ Gorby <russ.gorby@intel.com>
Tested-by: Kappel, LaurentX <laurentx.kappel@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Showjumping <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index a8c82f5..3e210a4 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -868,7 +868,7 @@
 
 	/* dlci->skb is locked by tx_lock */
 	if (dlci->skb == NULL) {
-		dlci->skb = skb_dequeue(&dlci->skb_list);
+		dlci->skb = skb_dequeue_tail(&dlci->skb_list);
 		if (dlci->skb == NULL)
 			return 0;
 		first = 1;
@@ -892,8 +892,11 @@
 
 	/* FIXME: need a timer or something to kick this so it can't
 	   get stuck with no work outstanding and no buffer free */
-	if (msg == NULL)
+	if (msg == NULL) {
+		skb_queue_tail(&dlci->skb_list, dlci->skb);
+		dlci->skb = NULL;
 		return -ENOMEM;
+	}
 	dp = msg->data;
 
 	if (dlci->adaption == 4) { /* Interruptible framed (Packetised Data) */