[PATCH 3.16.y-ckt 071/128] powerpc/powernv: Fix the overflow of OPAL message notifiers head array

[Luis Henriques]

3.16.7-ckt23 -stable review patch.  If anyone has any objections, please let me 
know.

---8<------------------------------------------------------------

From: Neelesh Gupta <neele...@linux.vnet.ibm.com>

commit 792f96e9a769b799a2944e9369e4ea1e467135b2 upstream.

Fixes the condition check of incoming message type which can
otherwise shoot beyond the message notifiers head array.

Signed-off-by: Neelesh Gupta <neele...@linux.vnet.ibm.com>
Reviewed-by: Vasant Hegde <hegdevas...@linux.vnet.ibm.com>
Reviewed-by: Anshuman Khandual <khand...@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Signed-off-by: Luis Henriques <luis.henriq...@canonical.com>
---
 arch/powerpc/platforms/powernv/opal.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal.c 
b/arch/powerpc/platforms/powernv/opal.c
index 199975613fe9..d5e5794db989 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -286,16 +286,12 @@ void opal_notifier_disable(void)
 int opal_message_notifier_register(enum OpalMessageType msg_type,
                                        struct notifier_block *nb)
 {
-       if (!nb) {
-               pr_warning("%s: Invalid argument (%p)\n",
-                          __func__, nb);
-               return -EINVAL;
-       }
-       if (msg_type > OPAL_MSG_TYPE_MAX) {
-               pr_warning("%s: Invalid message type argument (%d)\n",
+       if (!nb || msg_type >= OPAL_MSG_TYPE_MAX) {
+               pr_warning("%s: Invalid arguments, msg_type:%d\n",
                           __func__, msg_type);
                return -EINVAL;
        }
+
        return atomic_notifier_chain_register(
                                &opal_msg_notifier_head[msg_type], nb);
 }
@@ -332,7 +328,7 @@ static void opal_handle_message(void)
        type = be32_to_cpu(msg.msg_type);
 
        /* Sanity check */
-       if (type > OPAL_MSG_TYPE_MAX) {
+       if (type >= OPAL_MSG_TYPE_MAX) {
                pr_warning("%s: Unknown message type: %u\n", __func__, type);
                return;
        }