[PATCH] MdeModulePkg VariableSmm: Check InfoSize correctly

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

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=290

Current SmmVariableGetStatistics() in VariableSmm.c is always
checking input InfoSize against the first variable info,
it is incorrect.

For instance, there are three variables.
BootOrder
Boot0000
Boot0001

If the input InfoEntry is holding the second variable info (Boot0000)
and InfoSize is sizeof (VARIABLE_INFO_ENTRY) + StrSize (L"Boot0000"),
current code will return EFI_BUFFER_TOO_SMALL, but it should return
the third variable info (Boot0001).

This patch is to refine the code logic.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Star Zeng <star.zeng@intel.com>
---
 .../Universal/Variable/RuntimeDxe/VariableSmm.c    | 25 +++++++++++++++-------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c b/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c
index eafb53322e8c..85158d8b46ae 100644
--- a/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c
+++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmm.c
@@ -349,9 +349,10 @@ SmmVariableGetStatistics (
   )
 {
   VARIABLE_INFO_ENTRY                                  *VariableInfo;
-  UINTN                                                NameLength;
+  UINTN                                                NameSize;
   UINTN                                                StatisticsInfoSize;
   CHAR16                                               *InfoName;
+  UINTN                                                InfoNameMaxSize;
   EFI_GUID                                             VendorGuid;
 
   if (InfoEntry == NULL) {
@@ -363,12 +364,13 @@ SmmVariableGetStatistics (
     return EFI_UNSUPPORTED;
   }
 
-  StatisticsInfoSize = sizeof (VARIABLE_INFO_ENTRY) + StrSize (VariableInfo->Name);
+  StatisticsInfoSize = sizeof (VARIABLE_INFO_ENTRY);
   if (*InfoSize < StatisticsInfoSize) {
     *InfoSize = StatisticsInfoSize;
     return EFI_BUFFER_TOO_SMALL;
   }
   InfoName = (CHAR16 *)(InfoEntry + 1);
+  InfoNameMaxSize = (*InfoSize - sizeof (VARIABLE_INFO_ENTRY));
 
   CopyGuid (&VendorGuid, &InfoEntry->VendorGuid);
 
@@ -376,8 +378,14 @@ SmmVariableGetStatistics (
     //
     // Return the first variable info
     //
+    NameSize = StrSize (VariableInfo->Name);
+    StatisticsInfoSize = sizeof (VARIABLE_INFO_ENTRY) + NameSize;
+    if (*InfoSize < StatisticsInfoSize) {
+      *InfoSize = StatisticsInfoSize;
+      return EFI_BUFFER_TOO_SMALL;
+    }
     CopyMem (InfoEntry, VariableInfo, sizeof (VARIABLE_INFO_ENTRY));
-    CopyMem (InfoName, VariableInfo->Name, StrSize (VariableInfo->Name));
+    CopyMem (InfoName, VariableInfo->Name, NameSize);
     *InfoSize = StatisticsInfoSize;
     return EFI_SUCCESS;
   }
@@ -387,9 +395,9 @@ SmmVariableGetStatistics (
   //
   while (VariableInfo != NULL) {
     if (CompareGuid (&VariableInfo->VendorGuid, &VendorGuid)) {
-      NameLength = StrSize (VariableInfo->Name);
-      if (NameLength == StrSize (InfoName)) {
-        if (CompareMem (VariableInfo->Name, InfoName, NameLength) == 0) {
+      NameSize = StrSize (VariableInfo->Name);
+      if (NameSize <= InfoNameMaxSize) {
+        if (CompareMem (VariableInfo->Name, InfoName, NameSize) == 0) {
           //
           // Find the match one
           //
@@ -409,14 +417,15 @@ SmmVariableGetStatistics (
   //
   // Output the new variable info
   //
-  StatisticsInfoSize = sizeof (VARIABLE_INFO_ENTRY) + StrSize (VariableInfo->Name);
+  NameSize = StrSize (VariableInfo->Name);
+  StatisticsInfoSize = sizeof (VARIABLE_INFO_ENTRY) + NameSize;
   if (*InfoSize < StatisticsInfoSize) {
     *InfoSize = StatisticsInfoSize;
     return EFI_BUFFER_TOO_SMALL;
   }
 
   CopyMem (InfoEntry, VariableInfo, sizeof (VARIABLE_INFO_ENTRY));
-  CopyMem (InfoName, VariableInfo->Name, StrSize (VariableInfo->Name));
+  CopyMem (InfoName, VariableInfo->Name, NameSize);
   *InfoSize = StatisticsInfoSize;
 
   return EFI_SUCCESS;
-- 
2.7.0.windows.1