qed: Fix possible memory leak in Rx error path handling.

Memory for packet buffers need to be freed in the error paths as there is
no consumer (e.g., upper layer) for such packets and that memory will never
get freed.
The issue was uncovered when port was attacked with flood of isatap
packets, these are multicast packets hence were directed at all the PFs.
For foce PF, this meant they were routed to the ll2 module which in turn
drops such packets.

Fixes: 0a7fb11c ("qed: Add Light L2 support")
Signed-off-by: Sudarsana Reddy Kalluru <Sudarsana.Kalluru@cavium.com>
Signed-off-by: Ariel Elior <ariel.elior@cavium.com>
Signed-off-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qed/qed_ll2.c

@@ -201,8 +201,9 @@ void qed_ll2b_complete_rx_packet(void *cxt, struct qed_ll2_comp_rx_data *data)
 
 	skb = build_skb(buffer->data, 0);
 	if (!skb) {
-		rc = -ENOMEM;
-		goto out_post;
+		DP_INFO(cdev, "Failed to build SKB\n");
+		kfree(buffer->data);
+		goto out_post1;
 	}
 
 	data->u.placement_offset += NET_SKB_PAD;
@@ -224,8 +225,14 @@ void qed_ll2b_complete_rx_packet(void *cxt, struct qed_ll2_comp_rx_data *data)
 		cdev->ll2->cbs->rx_cb(cdev->ll2->cb_cookie, skb,
 				      data->opaque_data_0,
 				      data->opaque_data_1);
+	} else {
+		DP_VERBOSE(p_hwfn, (NETIF_MSG_RX_STATUS | NETIF_MSG_PKTDATA |
+				    QED_MSG_LL2 | QED_MSG_STORAGE),
+			   "Dropping the packet\n");
+		kfree(buffer->data);
 	}
 
+out_post1:
 	/* Update Buffer information and update FW producer */
 	buffer->data = new_data;
 	buffer->phys_addr = new_phys_addr;