--- 6bce2151a2d2325a73bdb8199ba4dcf7051d2405
+++ 73ffd5536f62d1fcbdd7b0c3804415436ebe4dc1
@@ -287,6 +287,25 @@ unsigned long __init_refok init_memory_m
 	load_cr3(swapper_pg_dir);
 #endif
 
+#ifdef CONFIG_X86_64
+	if (!after_bootmem && !start) {
+		pud_t *pud;
+		pmd_t *pmd;
+
+		mmu_cr4_features = read_cr4();
+
+		/*
+		 * _brk_end cannot change anymore, but it and _end may be
+		 * located on different 2M pages. cleanup_highmap(), however,
+		 * can only consider _end when it runs, so destroy any
+		 * mappings beyond _brk_end here.
+		 */
+		pud = pud_offset(pgd_offset_k(_brk_end), _brk_end);
+		pmd = pmd_offset(pud, _brk_end - 1);
+		while (++pmd <= pmd_offset(pud, (unsigned long)_end - 1))
+			pmd_clear(pmd);
+	}
+#endif
 	__flush_tlb_all();
 
 	if (!after_bootmem && e820_table_end > e820_table_start)