Re: [PATCH v27 03/21] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags

[Miklos Szeredi]

On Tue, Dec 6, 2016 at 10:13 PM, Jeremy Allison <jra@xxxxxxxxx> 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
>> > <agruenba@xxxxxxxxxx> 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.

Thanks,
Miklos