Re: [PATCH 0/2] Shared flags

[Christoph Hellwig <hch@infradead.org>]

On Tue, Nov 11, 2008 at 10:09:40AM +0000, Jamie Lokier wrote:
> Christoph Hellwig wrote:
> > On Mon, Nov 10, 2008 at 04:58:17PM +0300, Pavel Shilovsky wrote:
> > > #define O_DENYREAD      004000000 /* Do not permit read access */
> > > #define O_DENYWRITE     010000000 /* Do not permit write access */
> > > #define O_DENYDELETE  020000000 /* Do not permit delete or rename operations*/
> 
> >  (2) you also need to enforce these semantics in the VFS for local
> >      filesystems
> > 
> > Now if (2) doesn't cause too much overhead I would say it's fine, if not
> > I would rather avoid it.
> 
> On the face of it, they look like they have similar denial-of-service
> potential as mandatory locks.  For example, a root process cleaning
> out /tmp gets stuck because a user process has O_DENYDELETE set.

Oh, that's the part I forgot to mention in the previous mail, all of
these option of course can only be root only, everything else would
be - as you say - a complete security nightmare.