From: Andreas Gruenbacher Subject: Re: [PATCH v27 03/21] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags Date: Mon, 13 Feb 2017 16:40:41 +0100 Message-ID: References: <1476190256-1677-1-git-send-email-agruenba@redhat.com> <1476190256-1677-4-git-send-email-agruenba@redhat.com> <20161206201529.GA1203@fieldses.org> <20161206203347.GC4498@jra3> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Jeremy Allison , "J. Bruce Fields" , Alexander Viro , Christoph Hellwig , "Theodore Ts'o" , Andreas Dilger , Jeff Layton , Trond Myklebust , Anna Schumaker , Dave Chinner , "linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , LKML , linux-fsdevel , Linux NFS list , linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux API To: Miklos Szeredi Return-path: In-Reply-To: Sender: linux-cifs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org On Tue, Dec 6, 2016 at 10:25 PM, Miklos Szeredi wrote: > On Tue, Dec 6, 2016 at 10:13 PM, Jeremy Allison wrote: >> 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 >>> > 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). > > And MAY_DELETE_SELF as well, for rename? That's really counterintuitive for me. Yes, MAY_DELETE_SELF applies to delete as well as rename; otherwise rename() would behave different from link() + unlink(); when a user has the appropriate permissions, the result should be the same though. Thanks, Andreas