Fix a security hole in shell binaries:

For gBS->LoadImage() if the return status is EFI_SECURITY_VIOLATION, the image handle may not be NULL.
Shell environment should not have the assumption that the output ImageHandle must be NULL if the error status is returned by gBS->LoadImage().

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@9838 6f19259b-4bc3-4df7-8a09-765794883524

EdkShellBinPkg/SecurityPatch.diff

@@ -0,0 +1,15 @@
+Index: shellenv/exec.c
+===================================================================
+--- shellenv/exec.c	(revision 36)
++++ shellenv/exec.c	(working copy)
+@@ -2079,6 +2079,10 @@
+         if (!EFI_ERROR (Status)) {
+           goto Done;
+         } else {
++          //
++          // Set ImageHandle to NULL if any error status is returned.
++          //
++          ImageHandle = NULL;
+           Status = LibGetImageHeader (
+                      DevicePath,
+                      &DosHeader,