[PATCH] MdeModulePkg/Bds: Check variable name even OptionNumber is NULL

[Ruiyu Ni <ruiyu.ni@intel.com>]

Current implementation skips to check whether the last four
characters are digits when the OptionNumber is NULL.
Even worse, it may incorrectly return FALSE when OptionNumber is
NULL.

The patch fixes it to always check the variable name even
OptionNumber is NULL.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Laszlo Ersek <lersek@redhat.com>
---
 .../Library/UefiBootManagerLib/BmLoadOption.c      | 45 ++++++++++++++--------
 1 file changed, 30 insertions(+), 15 deletions(-)

diff --git a/MdeModulePkg/Library/UefiBootManagerLib/BmLoadOption.c b/MdeModulePkg/Library/UefiBootManagerLib/BmLoadOption.c
index b0a35058d0..32918caf32 100644
--- a/MdeModulePkg/Library/UefiBootManagerLib/BmLoadOption.c
+++ b/MdeModulePkg/Library/UefiBootManagerLib/BmLoadOption.c
@@ -785,6 +785,8 @@ EfiBootManagerIsValidLoadOptionVariableName (
   UINTN                             VariableNameLen;
   UINTN                             Index;
   UINTN                             Uint;
+  EFI_BOOT_MANAGER_LOAD_OPTION_TYPE LocalOptionType;
+  UINT16                            LocalOptionNumber;
 
   if (VariableName == NULL) {
     return FALSE;
@@ -792,39 +794,52 @@ EfiBootManagerIsValidLoadOptionVariableName (
 
   VariableNameLen = StrLen (VariableName);
 
+  //
+  // Return FALSE when the variable name length is too small.
+  //
   if (VariableNameLen <= 4) {
     return FALSE;
   }
 
-  for (Index = 0; Index < ARRAY_SIZE (mBmLoadOptionName); Index++) {
-    if ((VariableNameLen - 4 == StrLen (mBmLoadOptionName[Index])) &&
-        (StrnCmp (VariableName, mBmLoadOptionName[Index], VariableNameLen - 4) == 0)
+  //
+  // Return FALSE when the variable name doesn't start with Driver/SysPrep/Boot/PlatformRecovery.
+  //
+  for (LocalOptionType = 0; LocalOptionType < ARRAY_SIZE (mBmLoadOptionName); LocalOptionType++) {
+    if ((VariableNameLen - 4 == StrLen (mBmLoadOptionName[LocalOptionType])) &&
+        (StrnCmp (VariableName, mBmLoadOptionName[LocalOptionType], VariableNameLen - 4) == 0)
         ) {
       break;
     }
   }
+  if (LocalOptionType == ARRAY_SIZE (mBmLoadOptionName)) {
+    return FALSE;
+  }
 
-  if (Index == ARRAY_SIZE (mBmLoadOptionName)) {
+  //
+  // Return FALSE when the last four characters are not hex digits.
+  //
+  LocalOptionNumber = 0;
+  for (Index = VariableNameLen - 4; Index < VariableNameLen; Index++) {
+    Uint = BmCharToUint (VariableName[Index]);
+    if (Uint == -1) {
+      break;
+    } else {
+      LocalOptionNumber = (UINT16) Uint + LocalOptionNumber * 0x10;
+    }
+  }
+  if (Index != VariableNameLen) {
     return FALSE;
   }
 
   if (OptionType != NULL) {
-    *OptionType = (EFI_BOOT_MANAGER_LOAD_OPTION_TYPE) Index;
+    *OptionType = LocalOptionType;
   }
 
   if (OptionNumber != NULL) {
-    *OptionNumber = 0;
-    for (Index = VariableNameLen - 4; Index < VariableNameLen; Index++) {
-      Uint = BmCharToUint (VariableName[Index]);
-      if (Uint == -1) {
-        break;
-      } else {
-        *OptionNumber = (UINT16) Uint + *OptionNumber * 0x10;
-      }
-    }
+    *OptionNumber = LocalOptionNumber;
   }
 
-  return (BOOLEAN) (Index == VariableNameLen);
+  return TRUE;
 }
 
 /**
-- 
2.12.2.windows.2