rtlwifi: Avoid modifying skbs that are resubmitted

In the case we fail to allocate a new skb, the old skb should
be resubmitted unmodified.

Fixes bug introduced in a9e12869758430424804.

Signed-off-by: Mike McCormack <mikem@ring3k.org>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/pci.c

@@ -669,6 +669,19 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
 							 &rx_status,
 							 (u8 *) pdesc, skb);
 
+			new_skb = dev_alloc_skb(rtlpci->rxbuffersize);
+			if (unlikely(!new_skb)) {
+				RT_TRACE(rtlpriv, (COMP_INTR | COMP_RECV),
+					 DBG_DMESG,
+					 ("can't alloc skb for rx\n"));
+				goto done;
+			}
+
+			pci_unmap_single(rtlpci->pdev,
+					 *((dma_addr_t *) skb->cb),
+					 rtlpci->rxbuffersize,
+					 PCI_DMA_FROMDEVICE);
+
 			skb_put(skb, rtlpriv->cfg->ops->get_desc((u8 *) pdesc,
 							 false,
 							 HW_DESC_RXPKT_LEN));
@@ -685,21 +698,6 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
 			hdr = rtl_get_hdr(skb);
 			fc = rtl_get_fc(skb);
 
-			/* try for new buffer - if allocation fails, drop
-			 * frame and reuse old buffer
-			 */
-			new_skb = dev_alloc_skb(rtlpci->rxbuffersize);
-			if (unlikely(!new_skb)) {
-				RT_TRACE(rtlpriv, (COMP_INTR | COMP_RECV),
-					 DBG_DMESG,
-					 ("can't alloc skb for rx\n"));
-				goto done;
-			}
-			pci_unmap_single(rtlpci->pdev,
-					 *((dma_addr_t *) skb->cb),
-					 rtlpci->rxbuffersize,
-					 PCI_DMA_FROMDEVICE);
-
 			if (!stats.crc && !stats.hwerror) {
 				memcpy(IEEE80211_SKB_RXCB(skb), &rx_status,
 				       sizeof(rx_status));