diff --git a/mm/mm_heap/mm_free.c b/mm/mm_heap/mm_free.c
index 894719b056fa0..16b275cc0f3ba 100644
--- a/mm/mm_heap/mm_free.c
+++ b/mm/mm_heap/mm_free.c
@@ -72,6 +72,9 @@ void mm_free(FAR struct mm_heap_s *heap, FAR void *mem)
   FAR struct mm_freenode_s *node;
   FAR struct mm_freenode_s *prev;
   FAR struct mm_freenode_s *next;
+#ifdef CONFIG_MM_KASAN
+  size_t memsize;
+#endif
   int ret;
 
   UNUSED(ret);
@@ -84,12 +87,8 @@ void mm_free(FAR struct mm_heap_s *heap, FAR void *mem)
       return;
     }
 
-  kasan_poison(mem, mm_malloc_size(mem));
-
   if (mm_takesemaphore(heap) == false)
     {
-      kasan_unpoison(mem, mm_malloc_size(mem));
-
       /* Meet -ESRCH return, which means we are in situations
        * during context switching(See mm_takesemaphore() & getpid()).
        * Then add to the delay list.
@@ -99,6 +98,10 @@ void mm_free(FAR struct mm_heap_s *heap, FAR void *mem)
       return;
     }
 
+#ifdef CONFIG_MM_KASAN
+  memsize = mm_malloc_size(mem);
+#endif
+
   DEBUGASSERT(mm_heapmember(heap, mem));
 
   /* Map the memory chunk into a free node */
@@ -175,5 +178,10 @@ void mm_free(FAR struct mm_heap_s *heap, FAR void *mem)
   /* Add the merged node to the nodelist */
 
   mm_addfreechunk(heap, node);
+
+#ifdef CONFIG_MM_KASAN
+  kasan_poison(mem, memsize);
+#endif
+
   mm_givesemaphore(heap);
 }