linux-kernel - Re: [PATCH] cifs: Fix getting reparse points from server without WSL support

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Message-ID: <ZunnGhOogEQU2Hje@jeremy-rocky-laptop.localdomain>
Date: Tue, 17 Sep 2024 13:31:22 -0700
From: Jeremy Allison <jra@...ba.org>
To: Pali Rohár <pali@...nel.org>
Cc: Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.com>,
	linux-cifs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cifs: Fix getting reparse points from server without WSL
 support

On Tue, Sep 17, 2024 at 10:29:21PM +0200, Pali Rohár wrote:
>On Tuesday 17 September 2024 13:23:40 Jeremy Allison wrote:
>> On Tue, Sep 17, 2024 at 10:06:00PM +0200, Pali Rohár wrote:
>> > And seems that SMB2_OP_QUERY_WSL_EA is useful not only for reparse
>> > points, but also for any regular file or directory as it can contain
>> > UNIX mode and UID/GID ownership.
>>
>> uid/gid should *never* be exposed over the wire for SMB.
>>
>> That way lies madness.
>
>Hello Jeremy, if I understood wsl_to_fattr() function correctly then it
>is already doing it, it fills uid/gid for stat() from data which were
>exposed over the wire for SMB. Could you check that function if it is
>truth?

I'm sure the Windows implementation is doing it - however, any Linux
server implementations should not do this (IMHO).

It will break all SID -> uid / gid mapping that servers must
carefully set up.

On the wire - SIDs must be the only source of identity.