From 1b04c4369012b2d8b5c7d29526a0e00dd71c7742 Mon Sep 17 00:00:00 2001
From: Marco Cutecchia <marco.cutecchia@outlook.it>
Date: Sat, 1 Apr 2023 19:11:21 +0200
Subject: Kernel: Initialize DiskCache's buffer before the dirty&clean lists

This commit fixes a kernel panic that happened when unmounting
a disk due to an invalid memory access.
This was because `DiskCache` initializes two linked lists that use
an argument `KBuffer` as the storage for their elements.
Since the member `KBuffer` was declared after the two lists,
when `DiskCache`'s destructor was called, then `KBuffer`'s destructor
was called before the ones of the two lists, causing a page fault in
the kernel.
---
 Kernel/FileSystem/BlockBasedFileSystem.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

(limited to 'Kernel/FileSystem/BlockBasedFileSystem.cpp')

diff --git a/Kernel/FileSystem/BlockBasedFileSystem.cpp b/Kernel/FileSystem/BlockBasedFileSystem.cpp
index 4e78a5d3ed..1dabaecf00 100644
--- a/Kernel/FileSystem/BlockBasedFileSystem.cpp
+++ b/Kernel/FileSystem/BlockBasedFileSystem.cpp
@@ -101,11 +101,14 @@ public:
 
 private:
     mutable NonnullRefPtr<BlockBasedFileSystem> m_fs;
+    NonnullOwnPtr<KBuffer> m_cached_block_data;
+
+    // NOTE: m_entries must be declared before m_dirty_list and m_clean_list because their entries are allocated from it.
+    // We need to ensure that the destructors of m_dirty_list and m_clean_list are called before m_entries is destroyed.
+    NonnullOwnPtr<KBuffer> m_entries;
     mutable IntrusiveList<&CacheEntry::list_node> m_dirty_list;
     mutable IntrusiveList<&CacheEntry::list_node> m_clean_list;
     mutable HashMap<BlockBasedFileSystem::BlockIndex, CacheEntry*> m_hash;
-    NonnullOwnPtr<KBuffer> m_cached_block_data;
-    NonnullOwnPtr<KBuffer> m_entries;
 };
 
 BlockBasedFileSystem::BlockBasedFileSystem(OpenFileDescription& file_description)
-- 
cgit v1.2.3