[PATCH V2 2/3] MdeModulePkg Variable: Update GetNextVariableName to follow UEFI 2.7

[Star Zeng <star.zeng@intel.com>]

"The size must be large enough to fit input string supplied in
VariableName buffer" is added in the description for VariableNameSize.
And two cases of EFI_INVALID_PARAMETER are added.
1. The input values of VariableName and VendorGuid are not a name and
   GUID of an existing variable.
2. Null-terminator is not found in the first VariableNameSize bytes of
   the input VariableName buffer.

This patch is to update code to follow them.

Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
---
 .../Universal/Variable/EmuRuntimeDxe/EmuVariable.c | 25 +++++++++++++++++++++-
 .../Universal/Variable/RuntimeDxe/Variable.c       | 19 ++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Universal/Variable/EmuRuntimeDxe/EmuVariable.c b/MdeModulePkg/Universal/Variable/EmuRuntimeDxe/EmuVariable.c
index 27ea1496a044..6211ec52a439 100644
--- a/MdeModulePkg/Universal/Variable/EmuRuntimeDxe/EmuVariable.c
+++ b/MdeModulePkg/Universal/Variable/EmuRuntimeDxe/EmuVariable.c
@@ -3,7 +3,7 @@
   Emulation Variable services operate on the runtime volatile memory.
   The nonvolatile variable space doesn't exist.
 
-Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at
@@ -1245,6 +1245,10 @@ Done:
   @retval EFI_BUFFER_TOO_SMALL   VariableNameSize is too small for the result. 
                                  VariableNameSize has been updated with the size needed to complete the request.
   @retval EFI_INVALID_PARAMETER  VariableNameSize or VariableName or VendorGuid is NULL.
+  @retval EFI_INVALID_PARAMETER  The input values of VariableName and VendorGuid are not a name and
+                                 GUID of an existing variable.
+  @retval EFI_INVALID_PARAMETER  Null-terminator is not found in the first VariableNameSize bytes of
+                                 the input VariableName buffer.
 
 **/
 EFI_STATUS
@@ -1259,16 +1263,35 @@ EmuGetNextVariableName (
   VARIABLE_POINTER_TRACK  Variable;
   UINTN                   VarNameSize;
   EFI_STATUS              Status;
+  UINTN                   MaxLen;
 
   if (VariableNameSize == NULL || VariableName == NULL || VendorGuid == NULL) {
     return EFI_INVALID_PARAMETER;
   }
 
+  //
+  // Calculate the possible maximum length of name string, including the Null terminator.
+  //
+  MaxLen = *VariableNameSize / sizeof (CHAR16);
+  if ((MaxLen == 0) ||
+      ((VariableName[MaxLen - 1] != 0) && (StrnLenS (VariableName, MaxLen) == MaxLen))) {
+    //
+    // Null-terminator is not found in the first VariableNameSize bytes of the input VariableName buffer.
+    //
+    return EFI_INVALID_PARAMETER;
+  }
+
   AcquireLockOnlyAtBootTime(&Global->VariableServicesLock);
 
   Status = FindVariable (VariableName, VendorGuid, &Variable, Global);
 
   if (Variable.CurrPtr == NULL || EFI_ERROR (Status)) {
+    if (VariableName[0] != 0) {
+      //
+      // The input values of VariableName and VendorGuid are not a name and GUID of an existing variable.
+      //
+      Status = EFI_INVALID_PARAMETER;
+    }
     goto Done;
   }
 
diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c b/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
index 0a325de1659d..1e68c0a73a6d 100644
--- a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
+++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
@@ -2926,6 +2926,12 @@ VariableServiceGetNextVariableInternal (
 
   Status = FindVariable (VariableName, VendorGuid, &Variable, &mVariableModuleGlobal->VariableGlobal, FALSE);
   if (Variable.CurrPtr == NULL || EFI_ERROR (Status)) {
+    if (VariableName[0] != 0) {
+      //
+      // The input values of VariableName and VendorGuid are not a name and GUID of an existing variable.
+      //
+      Status = EFI_INVALID_PARAMETER;
+    }
     goto Done;
   }
 
@@ -3065,6 +3071,7 @@ VariableServiceGetNextVariableName (
   )
 {
   EFI_STATUS              Status;
+  UINTN                   MaxLen;
   UINTN                   VarNameSize;
   VARIABLE_HEADER         *VariablePtr;
 
@@ -3072,6 +3079,18 @@ VariableServiceGetNextVariableName (
     return EFI_INVALID_PARAMETER;
   }
 
+  //
+  // Calculate the possible maximum length of name string, including the Null terminator.
+  //
+  MaxLen = *VariableNameSize / sizeof (CHAR16);
+  if ((MaxLen == 0) ||
+      ((VariableName[MaxLen - 1] != 0) && (StrnLenS (VariableName, MaxLen) == MaxLen))) {
+    //
+    // Null-terminator is not found in the first VariableNameSize bytes of the input VariableName buffer.
+    //
+    return EFI_INVALID_PARAMETER;
+  }
+
   AcquireLockOnlyAtBootTime(&mVariableModuleGlobal->VariableGlobal.VariableServicesLock);
 
   Status = VariableServiceGetNextVariableInternal (VariableName, VendorGuid, &VariablePtr);
-- 
2.7.0.windows.1