linux-kernel - Re: [PATCH] procfs: make /proc style symlinks behave like "normal" symlinks

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Message-ID: <20091119213935.GA11212@elf.ucw.cz>
Date:	Thu, 19 Nov 2009 22:39:35 +0100
From:	Pavel Machek <pavel@....cz>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] procfs: make /proc style symlinks behave like "normal"
 symlinks

> > Adding all of the short comings to followlink that readlink has is a problem,
> > especially as followlink does much better now.
> > 
> > At a practical level I think your changes are much easier to exploit than
> > Pavels contrived example.
> > 
> > I really don't have any problems with your first patch to proc to add the
> > missing revalidate.
> > 
> 
> Thanks, that makes sense. The raciness was evident once you pointed it
> out, so I think you're correct that we can't take this approach.
> 
> Adding the missing revalidations is fine, but I don't believe that
> helps to fix Pavel's issue. I'll go back and take a more careful look
> at the suggestion that Miklos made and see whether it makes sense to
> implement a new FS_* flag for this, and see what it'll take to fix
> Pavel's issue.

One posibility would be to make open(/proc/XX/fd/XX) behave like
dup(). That should solve the NFS problems, too, no?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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