fix: kernel and desktop bug fixes

kernel/src/Memory/PageFrameAllocator.cpp

@@ -143,6 +143,17 @@ namespace Memory {
             return;
         }
 
+        // Overlap check: the new region must end at or before `current` starts.
+        // The previous double-free guards only matched single-page overlaps;
+        // freeing a multi-page span that overlaps the start of an existing
+        // block would silently corrupt the free list.
+        if (current != nullptr && addr + size > (uint64_t)current) {
+            Kt::KernelLogStream(Kt::WARNING, "PFA")
+                << "Overlapping free at " << addr << " size " << size << ", ignoring";
+            Lock.Release();
+            return;
+        }
+
         // Try to coalesce with previous block (if prev ends where new block starts)
         bool merged_prev = false;
         if (prev != &head) {