Messages in this thread | | | Date | Fri, 6 Nov 2009 15:17:42 +0100 | From | Pavel Machek <> | Subject | Re: [PATCH v2 resend] vfs: new O_NODE open flag |
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On Thu 2009-11-05 15:27:06, Miklos Szeredi wrote: > On Thu, 5 Nov 2009, Alan Cox wrote: > > > - re-opening normally after checking file type (there's a debate > > > whether this would have security issues, but currently we do allow > > > re-opening with increased permissions thorugh /proc/*/fd) > > > > Which has already been demonstrated to be an (unfixed) security hole. > > No it hasn't :) Jamie theorized that there *might* be a real world > situation where the application writer didn't anticipate this > behavior. But as to actual demonstration, we have not seen one yet, I > think.
See bugtraq, or lkml thread about symlinks with permissions. There's demo script there.
> And as for reopening O_NODE files with increased permission: that's > feature people actually expressed interest in, so it's hardly a > security hole, is it?
Just because people want it does not mean it is not a security hole.
Consider passing /etc/shadow filedesciptor to (legacy) suid root program. Maybe it now prints /etc/shadow content, because it assumes that if you have fd you are allowed to read the file?
Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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