From 48bbfe51fba186f995aefd7cfc5b1fc6ddf8ab01 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 1 Mar 2020 11:08:28 +0100
Subject: Kernel: Add some InodeVMObject type assertions in Region::clone()

Let's make sure that we're never cloning shared inode-backed objects
as if they were private, and vice versa.
---
 Kernel/VM/PrivateInodeVMObject.h | 2 ++
 Kernel/VM/Region.cpp             | 6 ++++++
 Kernel/VM/SharedInodeVMObject.h  | 2 ++
 Kernel/VM/VMObject.h             | 2 ++
 4 files changed, 12 insertions(+)

(limited to 'Kernel/VM')

diff --git a/Kernel/VM/PrivateInodeVMObject.h b/Kernel/VM/PrivateInodeVMObject.h
index 7f0d3998bc..ef65b51095 100644
--- a/Kernel/VM/PrivateInodeVMObject.h
+++ b/Kernel/VM/PrivateInodeVMObject.h
@@ -42,6 +42,8 @@ public:
     virtual NonnullRefPtr<VMObject> clone() override;
 
 private:
+    virtual bool is_private_inode() const override { return true; }
+
     explicit PrivateInodeVMObject(Inode&, size_t);
     explicit PrivateInodeVMObject(const PrivateInodeVMObject&);
 
diff --git a/Kernel/VM/Region.cpp b/Kernel/VM/Region.cpp
index a9f6b69727..dbe4e363c8 100644
--- a/Kernel/VM/Region.cpp
+++ b/Kernel/VM/Region.cpp
@@ -71,6 +71,9 @@ NonnullOwnPtr<Region> Region::clone()
 #ifdef MM_DEBUG
         dbg() << "Region::clone(): Sharing " << name() << " (" << vaddr() << ")";
 #endif
+        if (vmobject().is_inode())
+            ASSERT(vmobject().is_shared_inode());
+
         // Create a new region backed by the same VMObject.
         auto region = Region::create_user_accessible(m_range, m_vmobject, m_offset_in_vmobject, m_name, m_access);
         region->set_mmap(m_mmap);
@@ -78,6 +81,9 @@ NonnullOwnPtr<Region> Region::clone()
         return region;
     }
 
+    if (vmobject().is_inode())
+        ASSERT(vmobject().is_private_inode());
+
 #ifdef MM_DEBUG
     dbg() << "Region::clone(): CoWing " << name() << " (" << vaddr() << ")";
 #endif
diff --git a/Kernel/VM/SharedInodeVMObject.h b/Kernel/VM/SharedInodeVMObject.h
index f817ac673c..6f01c26fa8 100644
--- a/Kernel/VM/SharedInodeVMObject.h
+++ b/Kernel/VM/SharedInodeVMObject.h
@@ -42,6 +42,8 @@ public:
     virtual NonnullRefPtr<VMObject> clone() override;
 
 private:
+    virtual bool is_shared_inode() const override { return true; }
+
     explicit SharedInodeVMObject(Inode&, size_t);
     explicit SharedInodeVMObject(const SharedInodeVMObject&);
 
diff --git a/Kernel/VM/VMObject.h b/Kernel/VM/VMObject.h
index ff62f8d0a9..c108ea95a6 100644
--- a/Kernel/VM/VMObject.h
+++ b/Kernel/VM/VMObject.h
@@ -52,6 +52,8 @@ public:
     virtual bool is_anonymous() const { return false; }
     virtual bool is_purgeable() const { return false; }
     virtual bool is_inode() const { return false; }
+    virtual bool is_shared_inode() const { return false; }
+    virtual bool is_private_inode() const { return false; }
 
     size_t page_count() const { return m_physical_pages.size(); }
     const FixedArray<RefPtr<PhysicalPage>>& physical_pages() const { return m_physical_pages; }
-- 
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