diff --git a/mm/madvise.c b/mm/madvise.c
index af3d573..4e19615 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -168,6 +168,9 @@
 			return -EINVAL;
 	}
 
+	if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
+		return -EACCES;
+
 	mapping = vma->vm_file->f_mapping;
 
 	offset = (loff_t)(start - vma->vm_start)