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

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Message-ID: <20240917203431.w5dejuwfkmabrewz@pali>
Date: Tue, 17 Sep 2024 22:34:31 +0200
From: Pali Rohár <pali@...nel.org>
To: Jeremy Allison <jra@...ba.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 Tuesday 17 September 2024 13:31:22 Jeremy Allison wrote:
> 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.

Ok. But then I do not understand why Linux client parses and uses uid
and gids which are sent over the wire. If you are saying that the SIDs
must be the only source of truth then Linux client should rather ignore
uid and gid values?