Messages in this thread | | | Subject | Re: -mm -> 2.6.13 merge status (fuse) | From | Miklos Szeredi <> | Date | Wed, 22 Jun 2005 19:19:11 +0200 |
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> > It's related to the problem of a suid program accessing synthetic > > filesystem, and filesystem doing something bad to suid program (make > > it hang, supply bogus data ...). This can be solved by "squashing" > > suid for the whole namespace (basically the Plan 9 solution). > > Unfortunately this is not really practical in Linux/Unix. > > > > Just to make sure I understand you - if I don't squash suid for the > entire name space, a user could mount a malicious synthetic (even with > NOSUID) and then launch an SUID app from an inherited mount which > would then traverse to the malicious synthetic.
Yes.
> That's a nasty case I hadn't considered before -- however, what's the > potential damage there? The user could hold up progress of the SUID > app that they launched, but that wouldn't necessarily impede system > progress since system-critical suid apps wouldn't be typically > launched by a user. I suppose there is the possibility that if > multiple instances of such an SUID app share a global lock you could > get into trouble -- do we have any concrete example apps that would > exhibit this kind of behavior?
I don't know any. But with 'sudo' the potential set of SUID apps is basically infinite, so you'd have a hard time proving that this sort of situation won't arise.
> Are there other vunerabilities that I'm missing?
Another theoretical possibility is that you make the SUID app consume some resource by feeding it a large-file/deep-directory/etc that quota would otherwise prevent (you can't do quota on a synthetic filesystem, without the filesystem's cooperation).
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