[Bug sanitizer/57774] New: __libc_stack_end usage is broken

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57774

            Bug ID: 57774
           Summary: __libc_stack_end usage is broken
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: sanitizer
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
                CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
                    jakub at gcc dot gnu.org, kcc at gcc dot gnu.org

static void GetArgsAndEnv(char ***argv, char ***envp) {
  uptr *stack_end = (uptr *)__libc_stack_end;
  int argc = *stack_end;
  *argv = (char**)(stack_end + 1);
  *envp = (char**)(stack_end + argc + 2);
}

This is not a valid thing to do I think.  Since the user can change the values
after the fact.