NetworkPkg: PXE Driver's LoadFile protocol should check FilePath

PXE driver's LoadFile protocol should check the input parameter
FilePath to see whether it's a supported device path.If not,
it should return invalid parameter, do not continue PXE boot.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Zhang Lubo <lubo.zhang@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18436 6f19259b-4bc3-4df7-8a09-765794883524

NetworkPkg/UefiPxeBcDxe/PxeBcImpl.c

@@ -2328,6 +2328,10 @@ EfiPxeLoadFile (
   EFI_STATUS                  Status;
   BOOLEAN                     MediaPresent;
 
+  if (FilePath == NULL || !IsDevicePathEnd (FilePath)) {
+    return EFI_INVALID_PARAMETER;
+  }
+  
   VirtualNic = PXEBC_VIRTUAL_NIC_FROM_LOADFILE (This);
   Private    = VirtualNic->Private;
   PxeBc      = &Private->PxeBc;