RE: Windows absolute drive path detection incomplete

From: Christopher Ertl <christopher.ertl@microsoft.com>
Date: Aug 8, 2019, 16:58 UTC
Message-ID: <DB7PR83MB02682420A7444A60F8C9453997D70@DB7PR83MB0268.EURPRD83.prod.outlook.com>
In-Reply-To: <CAPig+cSuj6xWjYuQtuiuNQwroqO8sEh4iAGgLqQVOLQr8CMpDQ@mail.gmail.com>

Thanks, Eric, you're absolutely right; good spot!

Christopher Ertl | MSRC Vulnerabilities & Mitigations | Microsoft Limited Microsoft Limited (company number 01624297) is a company registered in England and Wales whose registered office is at Microsoft Campus, Thames Valley Park, Reading. RG6 1WG

-----Original Message-----
From: Eric Sunshine <sunshine@sunshineco.com> 
Sent: Thursday, August 8, 2019 5:51 PM
To: Christopher Ertl <Christopher.Ertl@microsoft.com>
Cc: git@vger.kernel.org
Subject: Re: Windows absolute drive path detection incomplete

On Thu, Aug 8, 2019 at 12:45 PM Christopher Ertl <Christopher.Ertl@microsoft.com> wrote:

> So I'm proposing to remove the check for the drive letter being alpha in `has_dos_drive_prefix` macro:
>
> #define has_dos_drive_prefix(path) \
>         ( (path)[1] == ':' ? 2 : 0)

Nit: This isn't safe and will access memory beyond end-of-string if path is zero-length. Perhaps something like this would be better:

    #define has_dos_drive_prefix(path) \
        (*(path) && (path)[1] == ':' ? 2 : 0)