From e346331424f98b05f2f0d362e0c291fd88d82aa4 Mon Sep 17 00:00:00 2001
From: Blake Smith <blakesmith0@gmail.com>
Date: Sun, 19 Nov 2023 19:15:37 -0600
Subject: [PATCH] Kernel/FS: Fix check-then-act concurrency bug in
 FileSystem/Inode

When the FileSystem does a sync, it gathers up all the inodes with
dirty metadata into a vector. The inode mutex is not held while
checking the inode dirty bit, which can lead to a kernel panic
due to concurrent inode modifications.

Fixes: #21796
---
 Kernel/FileSystem/Ext2FS/Inode.cpp | 3 +++
 Kernel/FileSystem/Inode.cpp        | 4 +---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/Kernel/FileSystem/Ext2FS/Inode.cpp b/Kernel/FileSystem/Ext2FS/Inode.cpp
index f0c600c5a3..3029a925f1 100644
--- a/Kernel/FileSystem/Ext2FS/Inode.cpp
+++ b/Kernel/FileSystem/Ext2FS/Inode.cpp
@@ -494,6 +494,9 @@ InodeMetadata Ext2FSInode::metadata() const
 ErrorOr<void> Ext2FSInode::flush_metadata()
 {
     MutexLocker locker(m_inode_lock);
+    if (!is_metadata_dirty())
+        return {};
+
     dbgln_if(EXT2_DEBUG, "Ext2FSInode[{}]::flush_metadata(): Flushing inode", identifier());
     TRY(fs().write_ext2_inode(index(), m_raw_inode));
     if (is_directory()) {
diff --git a/Kernel/FileSystem/Inode.cpp b/Kernel/FileSystem/Inode.cpp
index 52b15a4f72..89760dd24c 100644
--- a/Kernel/FileSystem/Inode.cpp
+++ b/Kernel/FileSystem/Inode.cpp
@@ -39,15 +39,13 @@ void Inode::sync_all()
     });
 
     for (auto& inode : inodes) {
-        VERIFY(inode->is_metadata_dirty());
         (void)inode->flush_metadata();
     }
 }
 
 void Inode::sync()
 {
-    if (is_metadata_dirty())
-        (void)flush_metadata();
+    (void)flush_metadata();
     auto result = fs().flush_writes();
     if (result.is_error()) {
         // TODO: Figure out how to propagate error to a higher function.