net: xgene: fix possible NULL dereference in xgene_enet_free_desc_rings()

A NULL pointer dereference is possible for the argument ring->buf_pool
which is passed to xgene_enet_free_desc_ring(), as ring could be NULL.

And now since NULL pointers are being checked for before the calls to
xgene_enet_free_desc_ring(), might as well take advantage of them and
not call the function if the argument would be NULL.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 7 deletions

diff --git a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
index e1a8f4e19983..e4222af2baa6 100644
--- a/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
+++ b/drivers/net/ethernet/apm/xgene/xgene_enet_main.c
@@ -563,15 +563,21 @@ static void xgene_enet_free_desc_rings(struct xgene_enet_pdata *pdata)
         struct xgene_enet_desc_ring *ring;
 
         ring = pdata->tx_ring;
-        if (ring && ring->cp_ring && ring->cp_ring->cp_skb)
-                devm_kfree(dev, ring->cp_ring->cp_skb);
-        xgene_enet_free_desc_ring(ring);
+        if (ring) {
+                if (ring->cp_ring && ring->cp_ring->cp_skb)
+                        devm_kfree(dev, ring->cp_ring->cp_skb);
+                xgene_enet_free_desc_ring(ring);
+        }
 
         ring = pdata->rx_ring;
-        if (ring && ring->buf_pool && ring->buf_pool->rx_skb)
-                devm_kfree(dev, ring->buf_pool->rx_skb);
-        xgene_enet_free_desc_ring(ring->buf_pool);
-        xgene_enet_free_desc_ring(ring);
+        if (ring) {
+                if (ring->buf_pool) {
+                        if (ring->buf_pool->rx_skb)
+                                devm_kfree(dev, ring->buf_pool->rx_skb);
+                        xgene_enet_free_desc_ring(ring->buf_pool);
+                }
+                xgene_enet_free_desc_ring(ring);
+        }
 }
 
 static struct xgene_enet_desc_ring *xgene_enet_create_desc_ring(