xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[ Upstream commit 4cc7c1cb ]
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/xen-netback/netback.c

@@ -950,7 +950,7 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 		pending_idx = netbk->pending_ring[index];
 		page = xen_netbk_alloc_page(netbk, skb, pending_idx);
 		if (!page)
-			return NULL;
+			goto err;
 
 		netbk->mmap_pages[pending_idx] = page;
 
@@ -974,6 +974,17 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 	}
 
 	return gop;
+err:
+	/* Unwind, freeing all pages and sending error responses. */
+	while (i-- > start) {
+		xen_netbk_idx_release(netbk, frag_get_pending_idx(&frags[i]),
+				      XEN_NETIF_RSP_ERROR);
+	}
+	/* The head too, if necessary. */
+	if (start)
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
+
+	return NULL;
 }
 
 static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,