Fix unsecure loading library pointed by ENV variable (#142)

* Adding function to check absolute path to avoid undefined behavior

src/ittnotify/jitprofiling.c

@@ -8,6 +8,8 @@
 
 #if ITT_PLATFORM==ITT_PLATFORM_WIN
 #include <windows.h>
+#include <string.h>
+#include <ctype.h>
 #endif /* ITT_PLATFORM==ITT_PLATFORM_WIN */
 #if ITT_PLATFORM != ITT_PLATFORM_MAC && ITT_PLATFORM != ITT_PLATFORM_FREEBSD && ITT_PLATFORM != ITT_PLATFORM_OPENBSD
 #include <malloc.h>
@@ -112,6 +114,28 @@ ITT_EXTERN_C iJIT_IsProfilingActiveFlags JITAPI iJIT_IsProfilingActive()
     return executionMode;
 }
 
+#if ITT_PLATFORM == ITT_PLATFORM_WIN
+static int isValidAbsolutePath(char *path)
+{
+    if (path == NULL)
+    {
+        return 0;
+    }
+    else if (strlen(path) > 2) 
+    {
+        if (isalpha(path[0]) && path[1] == ':' && path[2] == '\\')
+        {
+            return 1;
+        }
+        else if (path[0] == '\\' && path[1] == '\\')
+        {
+            return 1;
+        }
+    }
+    return 0;
+}
+#endif
+
 /* This function loads the collector dll and the relevant functions.
  * on success: all functions load,     iJIT_DLL_is_missing = 0, return value = 1
  * on failure: all functions are NULL, iJIT_DLL_is_missing = 1, return value = 0
@@ -155,7 +179,7 @@ static int loadiJIT_Funcs()
         {
             envret = GetEnvironmentVariableA(NEW_DLL_ENVIRONMENT_VAR, 
                                              dllName, dNameLength);
-            if (envret)
+            if (envret && isValidAbsolutePath(dllName))
             {
                 /* Try to load the dll from the PATH... */
                 m_libHandle = LoadLibraryExA(dllName,