Propagate LaunchInit error code by chemwolf6922 · Pull Request #41380 · microsoft/WSL

Feng Wang (chemwolf6922) · 2026-08-19T03:31:39Z

Summary of the Pull Request

LaunchInit currently try catch _exit(1) all exceptions. This could cause a files system failure being reported to the user as E_UNEXPECTED instead. For example: #13028 and #13237. Where the original EIO at step 3 were collapsed to E_UNEXPECTED.

This PR propagates the error out by removing LaunchInit's own try catch and rely on the caller's try catch logic. And also delays the closure of the original socket fd by setting it to CLOEXEC instead of manually close. So, the caller can still use it in catch.
This PR also adds EIO (5) at step 3 to the treated as disk corruption list.

PR Checklist

Closes: WSL2 cannot mount disk due to bad block bitmap checksum #13028, WSL fails to start - Catastrophic failure Error code: Wsl/Service/CreateInstance/E_UNEXPECTED #13237, Error code: Wsl/Service/CreateInstance/E_UNEXPECTED #13572. This PR helps with the error code but does not fix the original file system corruption issue.
Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
Tests: Added/updated if needed and all pass
Localization: All end user facing strings can be localized
Dev docs: Added/updated if needed
Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

Tested by manually injecting an error in LaunchInit:

The distribution failed to start because its virtual disk is corrupted.
Error code: Wsl/Service/CreateInstance/WSL_E_DISK_CORRUPTED

Copilot

Pull request overview

This PR adjusts the Linux-side mini-init launch path so that failures occurring during LaunchInit() are surfaced to the caller’s error-reporting logic (rather than being collapsed to a generic failure), improving the fidelity of error codes reported back to the Windows service during distro startup failures.

Changes:

Removed LaunchInit()’s internal try/catch that unconditionally _exit(1)’d, allowing exceptions to propagate to the caller that reports status.
Preserved the original launch socket FD for caller-side error reporting by setting FD_CLOEXEC (instead of closing it) after dup2().
Added exception logging in ProcessLaunchInitMessage()’s catch block before reporting failure.

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Blue (OneBlue)

I'm a bit confused by this. #13028 wasn't caused by an IO error, but by a VHD that's missing critical files (like passwd) so this change wouldn't affect that behavior.

Also if we want to cover mount related errors to display the "disk corrupted error", we also need to update this condition so that the LxInitCreateInstanceStepLaunchInit failure step also emits those

Feng Wang (chemwolf6922) · 2026-08-20T02:20:10Z

Hi Blue (@OneBlue) . Before the user tried to fix the file system. The error was LaunchInit fails with EIO because MountInit fails with EIO.
The file missing error was after the file system fix.

    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                   13,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758405979,          0,          0, "[    0.802792] EXT4-fs error (device sdd): ext4_validate_block_bitmap:421: comm LaunchDistro: bg 4185: bad block bitmap checksum ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                   11,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758408311,          0,          0, "[    0.803780] Aborting journal on device sdd-8. ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                    3,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758441048,          0,          0, "[    0.806941] EXT4-fs (sdd): Remounting filesystem read-only ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                    3,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758447325,          0,          0, "[    0.807373] WSL (1 - LaunchDistro) ERROR: CreateTempDirectory:560: mkdtemp(/distro/wslXXXXXX) failed 5 ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                    3,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758452044,          0,          0, "[    0.807982] WSL (1 - LaunchDistro) WARNING: Detected read-only or full filesystem. Adding a tmpfs overlay ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
Request_Tstatfs,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758457071,          0,          0,      0,        1
StorVspVsmbRelativeCreate,          1,            0,          0,         11,          4,          1,          0, 0x0000000000000100, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-7f43-1ff791d3db01},                                         ,   133933240758457177,          0,          0, 0xFFFF9D01EA1C3880, ""
StorvspVsmbDownlevelCreate,          1,            0,          0,         11,          4,          1,          0, 0x0000000000000100, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-8043-1ff791d3db01},   {f71eb5cb-d391-000b-7f43-1ff791d3db01},   133933240758457197,          0,          0, 0xFFFF9D01EA1C3880, ""
StorvspVsmbDownlevelCreate,          2,            0,          0,         11,          4,          2,          0, 0x0000000000000100, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-8043-1ff791d3db01},   {f71eb5cb-d391-000b-7f43-1ff791d3db01},   133933240758457631,          0,          0, 0xFFFF9D01EA1C3880, STATUS_SUCCESS
Microsoft-Windows-Hyper-V-StorageVSP ,          0,         1010,          0,         17,          4,          0,          0, 0x0000000000000004, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-7f43-1ff791d3db01},                                         ,   133933240758457674,          0,          0, "VspVsmbCommonRelativeCreate",     1363, "VspVsmbCommonRelativeCreate: Create  DA 0x100080 FA 0x2000080 SA 0x7 CD 0x1 CO 0x200000 eaBuffer 0000000000000000 eaLength 0 Imp? N bu? N status 0x00000000 info 0x1"
StorVspVsmbRelativeCreate,          2,            0,          0,         11,          4,          2,          0, 0x0000000000000100, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-7f43-1ff791d3db01},                                         ,   133933240758457781,          0,          0, 0xFFFF9D01EA1C3880, STATUS_SUCCESS
Reply_Rstatfs,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758458012,          0,          0,      0, 16914839,     4096,        243995647,        177407225,        177407225,              999,          1000000,                1,      255
Request_Tstatfs,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758459512,          0,          0,      0,        1
StorVspVsmbRelativeCreate,          1,            0,          0,         11,          4,          1,          0, 0x0000000000000100, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-8143-1ff791d3db01},                                         ,   133933240758459575,          0,          0, 0xFFFF9D01EA1C3EB0, ""
StorvspVsmbDownlevelCreate,          1,            0,          0,         11,          4,          1,          0, 0x0000000000000100, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-8243-1ff791d3db01},   {f71eb5cb-d391-000b-8143-1ff791d3db01},   133933240758459584,          0,          0, 0xFFFF9D01EA1C3EB0, ""
StorvspVsmbDownlevelCreate,          2,            0,          0,         11,          4,          2,          0, 0x0000000000000100, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-8243-1ff791d3db01},   {f71eb5cb-d391-000b-8143-1ff791d3db01},   133933240758459750,          0,          0, 0xFFFF9D01EA1C3EB0, STATUS_SUCCESS
Microsoft-Windows-Hyper-V-StorageVSP ,          0,         1010,          0,         17,          4,          0,          0, 0x0000000000000004, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-8143-1ff791d3db01},                                         ,   133933240758459773,          0,          0, "VspVsmbCommonRelativeCreate",     1363, "VspVsmbCommonRelativeCreate: Create  DA 0x100080 FA 0x2000080 SA 0x7 CD 0x1 CO 0x200000 eaBuffer 0000000000000000 eaLength 0 Imp? N bu? N status 0x00000000 info 0x1"
StorVspVsmbRelativeCreate,          2,            0,          0,         11,          4,          2,          0, 0x0000000000000100, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {f71eb5cb-d391-000b-8143-1ff791d3db01},                                         ,   133933240758459823,          0,          0, 0xFFFF9D01EA1C3EB0, STATUS_SUCCESS
Reply_Rstatfs,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x0000317C, 0x00001DB4,                   11,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758460084,          0,          0,      0, 16914839,     4096,        243995647,        177407225,        177407225,              999,          1000000,                1,      255
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                   11,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758468736,          0,          0, "[    0.809827] overlayfs: failed to get metacopy (-5) ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                   11,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758472323,          0,          0, "[    0.810095] WSL (1) ERROR: I/O error @main.cpp:2395 (MountInit) ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                   11,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758475600,          0,          0, "[    0.810437] WSL (1) ERROR: I/O error @main.cpp:1853 (LaunchInit) ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
       Error,          0,            0,          0,         11,          2,          0,          0, 0x0000000000000000, 0x000017E4, 0x00002E64,                   15,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758477600,         15,         15, "C:\__w\1\s\src\shared\inc\SocketChannel.h",      251,        0,        3,    11876, 0x8000FFFF, "Expected message LxMiniInitMessageCreateInstanceResult, but socket WslCorePort was closed", "", ""
CreateInstanceEnd,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00002E64,                   15,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758478565,         15,         15, "2.5.7.0",         16777216, "Ubuntu",        2, {2cdfb0e5-c0c1-448b-8c5a-28c3205b3020}, 0, -2147418113
  VerboseLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00002E64,                   15,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758480134,         15,         15, "C:\__w\1\s\src\windows\service\exe\LxssUserSession.cpp",      759,        4,    11876, 0x8000FFFF, "C:\__w\1\s\src\shared\inc\SocketChannel.h(251)\wslservice.exe!00007FF639F4A1A3: (caller: 00007FF639F93656) Exception(3) tid(2e64) 8000FFFF Katastrof�ln� selh�n�      Msg:[Expected message LxMiniInitMessageCreateInstanceResult, but socket WslCorePort was closed]  ", "", ""
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                    3,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758482414,          0,          0, "[    0.810969] WSL (1 - init-distro) ERROR: InitEntryUtilityVm:2572: Init has exited. Terminating distribution ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}
LxssException,          0,            0,          0,         11,          2,          0,          0, 0x0000000000000000, 0x00003178, 0x0000155C,                   15,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758482476,         15,          0, "C:\__w\1\s\src\windows\common\WslClient.cpp", "",      701,        0, 0x8000FFFF, "", ""
    GuestLog,          0,            0,          0,         11,          5,          0,          0, 0x0000000000000000, 0x000017E4, 0x00001C70,                   13,             ,                     ,   {00000000-0000-0000-0000-000000000000},                                         ,   133933240758492901,          0,          0, "[    0.812078] EXT4-fs (sdd): unmounting filesystem e1bd6dbd-cb4b-4bdc-b3b9-35a819be0d91. ", {759fed4d-944e-4c7d-a4c9-afcfde8482ce}

Feng Wang (chemwolf6922) · 2026-08-20T02:56:35Z

Also if we want to cover mount related errors to display the "disk corrupted error", we also need to update this condition so that the LxInitCreateInstanceStepLaunchInit failure step also emits those

I was a bit hesitant to treat all EIO in this step as disk corruption. But I guess it's ok.

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Suppressed comments (2)

src/linux/init/main.cpp:1502

SetCloseOnExec() is documented/implemented to return 0 on success and -1 on failure (main.cpp:3556-3559). Most call sites in this file compare the return value against < 0 (e.g., main.cpp:1048, 1053). Using THROW_LAST_ERROR_IF(SetCloseOnExec(...)) relies on implicit int-to-bool conversion and is inconsistent with the established pattern.

        THROW_LAST_ERROR_IF(SetCloseOnExec(SocketFd, true));

src/windows/service/exe/WslCoreInstance.cpp:71

Use the EIO errno constant instead of the magic value 5 for readability and to avoid baking in a numeric errno mapping.

        if (((result.Result == EINVAL || result.Result == 74 || result.Result == 117) && result.FailureStep == LxInitCreateInstanceStepMountDisk) ||
            (result.Result == 5 && result.FailureStep == LxInitCreateInstanceStepLaunchInit))

Feng Wang (chemwolf6922) · 2026-08-20T04:22:53Z

Note: used 5 instead of EIO. As the EIO in this file is the Windows EIO. Which happens to be the same as Linux.

Feng Wang (chemwolf6922) added 2 commits August 18, 2026 18:57

propagate launch init error

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Add back removed log

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Feng Wang (chemwolf6922) requested a review from a team as a code owner August 19, 2026 03:31

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Feng Wang (chemwolf6922) added 2 commits August 19, 2026 12:41

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Blue (OneBlue) requested changes Aug 19, 2026

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treat EIO at step 3 as disk corruption

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Feng Wang (chemwolf6922) merged commit 84ec12b into master Aug 21, 2026
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Feng Wang (chemwolf6922) deleted the user/chemwolf6922/propagate-launch-init-error branch August 21, 2026 02:25

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Propagate LaunchInit error code - #41380

Propagate LaunchInit error code#41380
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