From: Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
Subject: Re: [PATCH v27 03/21] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD
 permission flags
Date: Tue, 6 Dec 2016 13:13:58 -0800
Message-ID: <20161206203347.GC4498@jra3>
References: <1476190256-1677-1-git-send-email-agruenba@redhat.com>
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 <CAELBmZCgttywPy3EtkFao7SPESaw8VB5K6x7PTRk7gwSk7sXqg@mail.gmail.com>
 <20161206201529.GA1203@fieldses.org>
Reply-To: Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
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Cc: Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA@public.gmane.org>,
        Andreas Gruenbacher <agruenba-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
        Alexander Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
        Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
        Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org>,
        Andreas Dilger <adilger.kernel-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org>,
        Jeff Layton <jlayton-vpEMnDpepFuMZCB2o+C8xQ@public.gmane.org>,
        Trond Myklebust <trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org>,
        Anna Schumaker <anna.schumaker-HgOvQuBEEgTQT0dZR+AlfA@public.gmane.org>,
        Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
        LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
        linux-fsdevel <linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
        linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
        linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: "J. Bruce Fields" <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
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On Tue, Dec 06, 2016 at 03:15:29PM -0500, J. Bruce Fields wrote:
> On Fri, Dec 02, 2016 at 10:57:42AM +0100, Miklos Szeredi wrote:
> > On Tue, Oct 11, 2016 at 2:50 PM, Andreas Gruenbacher
> > <agruenba-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > > Normally, deleting a file requires MAY_WRITE access to the parent
> > > directory.  With richacls, a file may be deleted with MAY_DELETE_CHILD access
> > > to the parent directory or with MAY_DELETE_SELF access to the file.
> > >
> > > To support that, pass the MAY_DELETE_CHILD mask flag to inode_permission()
> > > when checking for delete access inside a directory, and MAY_DELETE_SELF
> > > when checking for delete access to a file itself.
> > >
> > > The MAY_DELETE_SELF permission overrides the sticky directory check.
> > 
> > And MAY_DELETE_SELF seems totally inappropriate to any kind of rename,
> > since from the point of view of the inode we are not doing anything at
> > all.  The modifications are all in the parent(s), and that's where the
> > permission checks need to be.
> 
> I'm having a hard time finding an authoritative reference here (Samba
> people might be able to help), but my understanding is that Windows
> gives this a meaning something like "may I delete a link to this file".
> 
> (And not even "may I delete the *last* link to this file", which might
> also sound more logical.)

I just did a recent patch here. In Samba we now check for
SEC_DIR_ADD_FILE/SEC_DIR_ADD_SUBDIR on the target directory
(depending on if the object being moved is a file or dir).