MdeModulePkg FileExplorerLib: Fix potential Integer Overflow.

In function 'LibAppendFileName' of 'FileExplorer.c':
"
MaxLen = (Size1 + Size2 + sizeof (CHAR16))/ sizeof (CHAR16);
"
Overflow may happen here. MaxLen might become a very small number.
This patch adds integer overflow checker.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

1 files changed, 26 insertions, 2 deletions

diff --git a/MdeModulePkg/Library/FileExplorerLib/FileExplorer.c b/MdeModulePkg/Library/FileExplorerLib/FileExplorer.c
index 59c851b7b3..41a22aa00c 100644
--- a/MdeModulePkg/Library/FileExplorerLib/FileExplorer.c
+++ b/MdeModulePkg/Library/FileExplorerLib/FileExplorer.c
@@ -620,6 +620,14 @@ LibAppendFileName (
 

   Size1 = StrSize (Str1);

   Size2 = StrSize (Str2);

+  

+  //

+  // Check overflow

+  //

+  if (((MAX_UINTN - Size1) < Size2) || ((MAX_UINTN - Size1 - Size2) < sizeof(CHAR16))) {

+    return NULL;

+  }

+  

   MaxLen = (Size1 + Size2 + sizeof (CHAR16))/ sizeof (CHAR16);

   Str   = AllocateZeroPool (Size1 + Size2 + sizeof (CHAR16));

   ASSERT (Str != NULL);

@@ -963,6 +971,7 @@ LibGetFileHandleFromDevicePath (
     // the file system support below to be skipped.

     //

     Status = EFI_OUT_OF_RESOURCES;

+    goto Done;

   }

         

   //

@@ -992,6 +1001,11 @@ LibGetFileHandleFromDevicePath (
       *ParentFileName = AllocateCopyPool (StrSize (((FILEPATH_DEVICE_PATH *) DevicePathNode)->PathName), ((FILEPATH_DEVICE_PATH *) DevicePathNode)->PathName);

     } else {

       TempPath = LibAppendFileName (*ParentFileName, ((FILEPATH_DEVICE_PATH *) DevicePathNode)->PathName);

+      if (TempPath == NULL) {

+        LastHandle->Close (LastHandle);

+        Status = EFI_OUT_OF_RESOURCES;

+        goto Done;

+      }

       FreePool (*ParentFileName);

       *ParentFileName = TempPath;

     }

@@ -1067,12 +1081,14 @@ LibFindFiles (
   // Pass 1 to get Directories

   // Pass 2 to get files that are EFI images

   //

+  Status = EFI_SUCCESS;

   for (Pass = 1; Pass <= 2; Pass++) {

     FileHandle->SetPosition (FileHandle, 0);

     for (;;) {

       BufferSize  = DirBufferSize;

       Status      = FileHandle->Read (FileHandle, &BufferSize, DirInfo);

       if (EFI_ERROR (Status) || BufferSize == 0) {

+        Status = EFI_SUCCESS;

         break;

       }

 

@@ -1095,12 +1111,18 @@ LibFindFiles (
 

       NewMenuEntry = LibCreateMenuEntry ();

       if (NULL == NewMenuEntry) {

-        return EFI_OUT_OF_RESOURCES;

+        Status = EFI_OUT_OF_RESOURCES;

+        goto Done;

       }

 

       NewFileContext = (FILE_CONTEXT *) NewMenuEntry->VariableContext;

       NewFileContext->DeviceHandle = DeviceHandle;

       NewFileContext->FileName = LibAppendFileName (FileName, DirInfo->FileName);

+      if  (NewFileContext->FileName == NULL) {

+        LibDestroyMenuEntry (NewMenuEntry);

+        Status = EFI_OUT_OF_RESOURCES;

+        goto Done;

+      }

       NewFileContext->FileHandle = FileHandle;

       NewFileContext->DevicePath = FileDevicePath (NewFileContext->DeviceHandle, NewFileContext->FileName);

       NewMenuEntry->HelpString = NULL;

@@ -1135,9 +1157,11 @@ LibFindFiles (
 

   gFileExplorerPrivate.FsOptionMenu->MenuNumber = OptionNumber;

 

+Done:

+

   FreePool (DirInfo);

 

-  return EFI_SUCCESS;

+  return Status;

 }

 

 /**