msm: msm_bus: Add NULL pointer checks.

Bus driver is crashing due to a NULL pointer
access sent by the client. A few NULL pointer
checks have been added to protect the driver
from invalid/NULL client handle.

CRs-Fixed: 458264
Change-Id: I822ad312ba1a0c0939d97eb92ea53094d408a836
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>

arch/arm/mach-msm/msm_bus/msm_bus_arb.c

@@ -1,4 +1,4 @@
-/* Copyright (c) 2011-2012, The Linux Foundation. All rights reserved.
+/* Copyright (c) 2011-2013, The Linux Foundation. All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 and
@@ -574,6 +574,10 @@ int msm_bus_scale_client_update_request(uint32_t cl, unsigned index)
 
 	curr = client->curr;
 	pdata = client->pdata;
+	if (!pdata) {
+		MSM_BUS_ERR("Null pdata passed to update-request\n");
+		return -ENXIO;
+	}
 
 	if (index >= pdata->num_usecases) {
 		MSM_BUS_ERR("Client %u passed invalid index: %d\n",
@@ -709,7 +713,7 @@ void msm_bus_scale_client_reset_pnodes(uint32_t cl)
 {
 	int i, src, pnode, index;
 	struct msm_bus_client *client = (struct msm_bus_client *)(cl);
-	if (IS_ERR(client)) {
+	if (IS_ERR_OR_NULL(client)) {
 		MSM_BUS_ERR("msm_bus_scale_reset_pnodes error\n");
 		return;
 	}
@@ -730,7 +734,7 @@ void msm_bus_scale_client_reset_pnodes(uint32_t cl)
 void msm_bus_scale_unregister_client(uint32_t cl)
 {
 	struct msm_bus_client *client = (struct msm_bus_client *)(cl);
-	if (IS_ERR(client) || (!client))
+	if (IS_ERR_OR_NULL(client))
 		return;
 	if (client->curr != 0)
 		msm_bus_scale_client_update_request(cl, 0);