[CFAPI] file handle from CfGetWin32HandleFromProtectedHandle cannot be used to read data.

Question

[CFAPI] file handle from CfGetWin32HandleFromProtectedHandle cannot be used to read data.

Aaron Liu 0

Hi,

I'm trying to implement a sync logic to upload local change to cloud. In this case I need to open local file for read, but it does not work as expected:

Get a protected handle protected_handle from CfOpenFileWithOplock, works fine;
Get a win32 handle win32_handle from CfReferenceProtectedHandle, then CfGetWin32HandleFromProtectedHandle, no errors.
Try to read using the win32 handle, go the error { code: 87, kind: InvalidInput, message: "The parameter is incorrect." }

I tried to dump the handle value, protected_handle=0x21e028574a1 looks a legit handle value, but win32_handle=0x808 looks weird, is this a expected handle value?

Also I want to confirm if my approach is correct for my scenario. Any help would be great. thanks!

Viorel 125.6K Reputation points

2025-12-03T11:02:26.82+00:00

Maybe the handle is valid, but another parameter is incorrect.
Aaron Liu 0 Reputation points

2025-12-03T11:45:40.07+00:00
Actually I'm using rust std to read the file from raw handle:

let file = unsafe { File::from_raw_handle(win32_handle.0 as *mut _) };

Under the hood it's invoking NtReadFile, it works fine with a raw handle opened with Rust std, but not works for handles from CfGetWin32HandleFromProtectedHandle

Seek method works well though……
Viorel 125.6K Reputation points

2025-12-03T12:15:59.5433333+00:00

Maybe the handle is supposed to be used with ReadFile.

1 answer

Your answer

Viorel 125.6K Reputation points

2025-12-03T11:02:26.82+00:00

Maybe the handle is valid, but another parameter is incorrect.
Aaron Liu 0 Reputation points

2025-12-03T11:45:40.07+00:00

Actually I'm using rust std to read the file from raw handle:

let file = unsafe { File::from_raw_handle(win32_handle.0 as *mut _) };

Under the hood it's invoking NtReadFile, it works fine with a raw handle opened with Rust std, but not works for handles from CfGetWin32HandleFromProtectedHandle

Seek method works well though……
Viorel 125.6K Reputation points

2025-12-03T12:15:59.5433333+00:00

Maybe the handle is supposed to be used with ReadFile.

Answer 1

Hello @Aaron Liu ,

Thank you for reaching out.

Based on your description, your approach seems correct. For error like InvalidInput, there are a few things you can check for:

Protected handle validity — ensure you didn’t already close it or lose it due to an oplock break.
Oplock callbacks — make sure you acknowledge any oplock break promptly.
Handle lifetime — don’t hold the Win32 handle too long; use it briefly and close it.
Share/access modes — verify the access flags passed to CfOpenFileWithOplock aren’t conflicting.
Interference — antivirus or indexing can steal/break the lock.
Correct cleanup — close the Win32 handle with CloseHandle, and the protected handle with CfCloseHandle.

I hope this is helpful for your issue. If it does not work, I would appreciate if you can provide me more detail of the issue.

Share via

[CFAPI] file handle from CfGetWin32HandleFromProtectedHandle cannot be used to read data.

1 answer

Your answer