[New-bugs-announce] [issue38030] os.stat fails for block devices such as //./PhysicalDrive0

[Eryk Sun]

New submission from Eryk Sun <eryksun at gmail.com>:

In issue 37834, I posted a suggest implementation of win32_xstat_impl that included the following snippet of code:

        if (!GetFileInformationByHandle(hFile, &fileInfo)) {
            error = GetLastError();
            if (error != ERROR_INVALID_PARAMETER &&
                error != ERROR_INVALID_FUNCTION &&
                error != ERROR_NOT_SUPPORTED) {
                retval = -1;
                goto cleanup;
            }
            /* Volumes and physical disks are block devices, e.g.
               \\.\C: and \\.\PhysicalDrive0. */
            memset(result, 0, sizeof(*result));
            result->st_mode = 0x6000; /* S_IFBLK */
            goto cleanup;
        }

This is meant to handle the above errors. We know we have FILE_TYPE_DISK. If GetFileInformationByHandle fails with one of the above error codes, then we must have a disk or volume device without a mounted file-system device. This should be reported as a block device.

However it was changed in the final version as follows:

        if (!GetFileInformationByHandle(hFile, &fileInfo)) {
            switch (GetLastError()) {
            case ERROR_INVALID_PARAMETER:
            case ERROR_INVALID_FUNCTION:
            case ERROR_NOT_SUPPORTED:
                retval = -1;
                goto cleanup;
            }
            /* Volumes and physical disks are block devices, e.g.
               \\.\C: and \\.\PhysicalDrive0. */
            memset(result, 0, sizeof(*result));
            result->st_mode = 0x6000; /* S_IFBLK */
            goto cleanup;
        }

Now it's failing on the errors that should be handled, and succeeding on all other errors that should fail. If we want to use a switch statement here, I suggest the following:

        if (!GetFileInformationByHandle(hFile, &fileInfo)) {
            switch (GetLastError()) {
            case ERROR_INVALID_PARAMETER:
            case ERROR_INVALID_FUNCTION:
            case ERROR_NOT_SUPPORTED:
                /* Volumes and physical disks are block devices, e.g.
                   \\.\C: and \\.\PhysicalDrive0. */
                memset(result, 0, sizeof(*result));
                result->st_mode = 0x6000; /* S_IFBLK */
                goto cleanup;
            }
            retval = -1;
            goto cleanup;
        }

----------
components: IO, Windows
messages: 351149
nosy: eryksun, paul.moore, steve.dower, tim.golden, zach.ware
priority: high
severity: normal
stage: needs patch
status: open
title: os.stat fails for block devices such as //./PhysicalDrive0
type: behavior
versions: Python 3.8, Python 3.9

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue38030>
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