From 5c154986094bcc2fb28909cc5f01c9ba1dd9ddd4 Mon Sep 17 00:00:00 2001 From: qmuntal Date: Tue, 4 Jul 2023 13:39:41 +0200 Subject: [PATCH] os: support reading empty root directories on Windows GetFileInformationByHandleEx can return `ERROR_FILE_NOT_FOUND` when no files were found in a root directory, as per MS-FSA 2.1.5.6.3 [1]. This error code should not be treated as an error, but rather as an indication that no files were found, in which case `readdir` should return an empty slice. This CL doesn't add any test as it is difficult to trigger this error code. Empty root directories created using Windows utilities such as `net use` always report at least the optional `.` and `..` entries. A reproducer is provided in #61159, but it requires WinFSP to be installed. Fixes #61159 [1] https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-fsa/fa8194e0-53ec-413b-8315-e8fa85396fd8 Change-Id: Id46452030f5355c292e5b0abbf5e22af434a84d2 Reviewed-on: https://go-review.googlesource.com/c/go/+/507775 Reviewed-by: Nick Craig-Wood TryBot-Result: Gopher Robot Run-TryBot: Quim Muntal Reviewed-by: Heschi Kreinick Reviewed-by: Bryan Mills --- src/os/dir_windows.go | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/src/os/dir_windows.go b/src/os/dir_windows.go index 7792d03040..1724af58d5 100644 --- a/src/os/dir_windows.go +++ b/src/os/dir_windows.go @@ -84,6 +84,18 @@ func (file *File) readdir(n int, mode readdirMode) (names []string, dirents []Di if err == syscall.ERROR_NO_MORE_FILES { break } + if infoClass == windows.FileIdBothDirectoryRestartInfo && err == syscall.ERROR_FILE_NOT_FOUND { + // GetFileInformationByHandleEx doesn't document the return error codes when the info class is FileIdBothDirectoryRestartInfo, + // but MS-FSA 2.1.5.6.3 [1] specifies that the underlying file system driver should return STATUS_NO_SUCH_FILE when + // reading an empty root directory, which is mapped to ERROR_FILE_NOT_FOUND by Windows. + // Note that some file system drivers may never return this error code, as the spec allows to return the "." and ".." + // entries in such cases, making the directory appear non-empty. + // The chances of false positive are very low, as we know that the directory exists, else GetVolumeInformationByHandle + // would have failed, and that the handle is still valid, as we haven't closed it. + // See go.dev/issue/61159. + // [1] https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-fsa/fa8194e0-53ec-413b-8315-e8fa85396fd8 + break + } if s, _ := file.Stat(); s != nil && !s.IsDir() { err = &PathError{Op: "readdir", Path: file.name, Err: syscall.ENOTDIR} } else {