Re: [PATCH 0/3] vfs: plug some holes involving LAST_BIND symlinks and file bind mounts (try #5)

Pavel Machek
2009-11-24T12:28:17Z

On Tue 2009-11-24 12:53:09, Miklos Szeredi wrote:
> On Tue, 24 Nov 2009, Jeff Layton wrote:
> > Since it's clear that these symlinks do need to have special semantics,
> > perhaps the approach you suggest would be the best thing. I'll have to
> > think about it a bit more.
>
> open() is not the only thing you need to think about. Anything that
> checks read or write permission on the inode (truncate, utimes,
> *xattr) would have to be changed to respect the open mode.
>
> See, this is not just about hacking the proc follow_symlink code to
> check some lookup intent. It's about changing the permission checking
> mechanism for theses beasts. And since the permission checking is
> inode based, this is not at all trivial to do.
>
> I still believe leaving the current semantics and documenting them is
> the best option.

I believe that current semantics is ugly enough that 'documenting' it
is not enough... and people want to port from other systems, too, not
expecting nasty surprises like this...
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html