fix: frame allocation now invalidates the victim process page directory, not the caller's

src/vm/frame.c

@@ -96,7 +96,7 @@ frame_alloc (enum palloc_flags flags, void *upage, struct thread *owner)
       /* Mark page as 'not present' and flag the page directory as having
          been modified *before* eviction begins to prevent the owner of the
          victim page from accessing/modifying it mid-eviction. */
-      pagedir_clear_page (owner->pagedir, upage);
+      pagedir_clear_page (victim->owner->pagedir, victim->upage);
 
       // TODO: Lock PTE of victim page for victim process.