git kdiff3 on Ubuntu subsystem

I use kdiff3 in git bash as git difftooland I encountered a problem to use it under Ubuntu subsystem.Ubuntu subsystem has already Git installed.So I copied my Git global config from Git Bash (changing the path accordingly):

[user]    email = ...    name = ...[merge]    tool = kdiff3[mergetool "kdiff3"]    path = "/mnt/c/Program Files/KDiff3/kdiff3.exe"[diff]    tool = kdiff3    guitool = kdiff3[difftool "kdiff3"]    path = "/mnt/c/Program Files/KDiff3/kdiff3.exe"[core]    autocrlf = true

Then I encountered an error:

Opening of these files failed- [filename].[extension] (A)

The program window opened correctly, but only the right side file (B) was displayed.

The error is repeatable every time.Anyone know what can cause this error?