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Fix system.vhd loss during failed MSI upgrade #40524

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Fix system.vhd loss during failed MSI upgrade #40524

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4 changes: 4 additions & 0 deletions localization/strings/en-US/Resources.resw
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Original file line number Diff line number Diff line change
Expand Up @@ -652,6 +652,10 @@ Build time: {}</value>
<value>The custom system distribution specified in {} was not found or is not the correct format.</value>
<comment>{FixedPlaceholder="{}"}Command line arguments, file names and string inserts should not be translated</comment>
</data>
<data name="MessageSystemDistroMissing" xml:space="preserve">
<value>A required WSL package file is missing: '{}'. Please run 'wsl --update' to restore it.</value>
<comment>{FixedPlaceholder="{}"}Command line arguments, file names and string inserts should not be translated. {Locked="WSL"} {Locked="wsl --update"}</comment>
</data>
<data name="MessageWslgUsage" xml:space="preserve">
<value>Copyright (c) Microsoft Corporation. All rights reserved.
For privacy information about this product please visit https://aka.ms/privacy.
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2 changes: 1 addition & 1 deletion msipackage/package.wix.in
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@@ -1,6 +1,6 @@
<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs">
<Package Name="Windows Subsystem for Linux" Language="1033" InstallerVersion="500" Version="${PACKAGE_VERSION}" Manufacturer="Microsoft Corporation" UpgradeCode="6D5B792B-1EDC-4DE9-8EAD-201B820F8E82" Scope="perMachine" Compressed="${COMPRESS_PACKAGE}">
<MajorUpgrade AllowDowngrades="yes" Disallow="no" />
<MajorUpgrade AllowDowngrades="yes" Disallow="no" Schedule="afterInstallInitialize" />
<MediaTemplate EmbedCab="yes" />

<StandardDirectory Id="ProgramFiles64Folder">
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6 changes: 6 additions & 0 deletions src/windows/common/wslutil.cpp
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Expand Up @@ -87,6 +87,7 @@ static const std::map<HRESULT, LPCWSTR> g_commonErrors{
X(WSL_E_DISTRIBUTION_NAME_NEEDED),
X(WSL_E_INVALID_JSON),
X(WSL_E_VM_CRASHED),
X(WSL_E_SYSTEM_DISTRO_MISSING),
X(WSL_E_NOT_A_LINUX_DISTRO),
X(WSLC_E_CONTAINER_PREFIX_AMBIGUOUS),
X(E_ACCESSDENIED),
Expand Down Expand Up @@ -783,6 +784,11 @@ std::wstring wsl::windows::common::wslutil::GetErrorString(HRESULT result)
case WSL_E_NOT_A_LINUX_DISTRO:
return Localization::MessageInvalidDistributionTar();

case WSL_E_SYSTEM_DISTRO_MISSING:
// Generic fallback for paths that don't set a specific user message (e.g., WSLC).
// WslCoreVm.cpp paths use THROW_HR_WITH_USER_ERROR_IF with the specific missing path.
return Localization::MessageSystemDistroMissing(wslutil::GetMsiPackagePath().value_or(L""));

case WSL_E_INVALID_USAGE:
{
const auto* context = wsl::windows::common::ExecutionContext::Current();
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10 changes: 10 additions & 0 deletions src/windows/service/exe/HcsVirtualMachine.cpp
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Expand Up @@ -21,6 +21,7 @@ Module Name:
#include "NatNetworking.h"
#include "wslsecurity.h"
#include "wslutil.h"
#include "filesystem.hpp"
#include "lxinitshared.h"
#include "DnsResolver.h"

Expand Down Expand Up @@ -221,6 +222,15 @@ HcsVirtualMachine::HcsVirtualMachine(_In_ const WSLCSessionSettings* Settings)
#endif
}

// Validate required package files exist before attempting to attach them.
// Only check default (non-override) paths — overrides are user-provided.
if (Settings->RootVhdOverride == nullptr)
{
THROW_HR_IF(WSL_E_SYSTEM_DISTRO_MISSING, !wsl::windows::common::filesystem::FileExists(rootVhdPath.c_str()));
}

THROW_HR_IF(WSL_E_SYSTEM_DISTRO_MISSING, !wsl::windows::common::filesystem::FileExists(kernelModulesPath.c_str()));
Comment on lines +229 to +232
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@yeelam-gordon yeelam-gordon May 14, 2026

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By design — HcsVirtualMachine.cpp doesn't have ExecutionContext. The fallback in GetErrorString now uses GetMsiPackagePath() so users get a meaningful message.


// Setup boot VHDs
hcs::Scsi scsiController{};
auto attachScsiDisk = [&](PCWSTR path) {
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9 changes: 8 additions & 1 deletion src/windows/service/exe/WslCoreVm.cpp
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Expand Up @@ -232,6 +232,10 @@ void WslCoreVm::Initialize(const GUID& VmId, const wil::shared_handle& UserToken
#else

m_vmConfig.KernelModulesPath = m_rootFsPath / L"modules.vhd";
THROW_HR_WITH_USER_ERROR_IF(
WSL_E_SYSTEM_DISTRO_MISSING,
Localization::MessageSystemDistroMissing(m_vmConfig.KernelModulesPath),
!wsl::windows::common::filesystem::FileExists(m_vmConfig.KernelModulesPath.c_str()));

#endif
}
Expand Down Expand Up @@ -1421,7 +1425,10 @@ std::wstring WslCoreVm::GenerateConfigJson()

m_systemDistroDeviceType = LxMiniInitMountDeviceTypeLun;
m_vmConfig.SystemDistroPath = (m_installPath / L"system.vhd").wstring();
WI_ASSERT(wsl::windows::common::filesystem::FileExists(m_vmConfig.SystemDistroPath.c_str()));
THROW_HR_WITH_USER_ERROR_IF(
WSL_E_SYSTEM_DISTRO_MISSING,
Localization::MessageSystemDistroMissing(m_vmConfig.SystemDistroPath),
!wsl::windows::common::filesystem::FileExists(m_vmConfig.SystemDistroPath.c_str()));
Comment on lines +1428 to +1431
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@yeelam-gordon yeelam-gordon May 14, 2026

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Manual runtime rollback test documented in PR comments validates the core scenario (locked file → install failure → rollback → VHDs intact). Automated test would require deleting system.vhd from a live install — happy to add in a follow-up PR.


#endif
}
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1 change: 1 addition & 0 deletions src/windows/service/inc/wslservice.idl
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Expand Up @@ -395,3 +395,4 @@ cpp_quote("#define WSL_E_DISK_CORRUPTED MAKE_HRESULT(SEVERITY_ERROR, FACILITY_IT
cpp_quote("#define WSL_E_DISTRIBUTION_NAME_NEEDED MAKE_HRESULT(SEVERITY_ERROR, FACILITY_ITF, WSL_E_BASE + 0x30) /* 0x80040330 */")
cpp_quote("#define WSL_E_INVALID_JSON MAKE_HRESULT(SEVERITY_ERROR, FACILITY_ITF, WSL_E_BASE + 0x31) /* 0x80040331 */")
cpp_quote("#define WSL_E_VM_CRASHED MAKE_HRESULT(SEVERITY_ERROR, FACILITY_ITF, WSL_E_BASE + 0x32) /* 0x80040332 */")
cpp_quote("#define WSL_E_SYSTEM_DISTRO_MISSING MAKE_HRESULT(SEVERITY_ERROR, FACILITY_ITF, WSL_E_BASE + 0x33) /* 0x80040333 */")