From 9790b81959fc31e0690380ef5c3b6e7e4a6b9802 Mon Sep 17 00:00:00 2001
From: Liav A <liavalb@gmail.com>
Date: Sat, 18 Feb 2023 16:44:16 +0200
Subject: [PATCH] Kernel/FileSystem: Add check of read offset for the FATInode
 code

Apparently we lacked this important check from the beginning of this
piece of code. This check is crucial to ensure we only give back data
being related to the FATInode data buffer and nothing beyond it.
---
 Kernel/FileSystem/FATFS/Inode.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Kernel/FileSystem/FATFS/Inode.cpp b/Kernel/FileSystem/FATFS/Inode.cpp
index 0dcd95468c..6683a77917 100644
--- a/Kernel/FileSystem/FATFS/Inode.cpp
+++ b/Kernel/FileSystem/FATFS/Inode.cpp
@@ -201,6 +201,9 @@ u32 FATInode::first_cluster() const
 ErrorOr<size_t> FATInode::read_bytes_locked(off_t offset, size_t size, UserOrKernelBuffer& buffer, OpenFileDescription*) const
 {
     dbgln_if(FAT_DEBUG, "FATFS: Reading inode {}: size: {} offset: {}", identifier().index(), size, offset);
+    VERIFY(offset >= 0);
+    if (offset >= m_metadata.size)
+        return 0;
 
     // FIXME: Read only the needed blocks instead of the whole file
     auto blocks = TRY(const_cast<FATInode&>(*this).read_block_list());