Messages in this thread | | | Subject | Re: [PATCH] private mounts | From | Miklos Szeredi <> | Date | Wed, 27 Apr 2005 19:52:25 +0200 |
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> > > the ability to change the layout underneath, you might trigger bugs in > > > root programs: Are they really capable of seeing the same filename > > > twice, or can you throw them into a deep recursion by simulating > > > infinitely deep directories/circular hardlinks...? > > Circular or otherwise hardlinked directories are not allowed since it > > would not only confuse applications but the VFS as well. > > Right, that you can catch. But can you prevent a user fs module from > creating an infinitely deep directory structure out of thin air? Do you > limit the maximum path length / depth?
No.
> (Sending this privately and not to LKML, because I first wanted to check > the facts ;-)
OK, CC restored. You shouldn't be afraid to send to LKML. It's the ultimate spam list ;)
> > > Certainly a useful tool for hardening applications, but I can see the > > > point of not wanting to let unwary applications run into a namespace > > > controlled by a user. Of course, this is sort-of similar to "find > > > -xdev", but I'm not sure whether it is not indeed new behaviour. > > > > A trivial DoS against any process entering the userspace filesystem is > > just not to answer the filesystem request. > > > > So it's not just information leak, but also a fine way to _control_ > > certain behavior of applications. > > Yes. I first thought the check was superfluous, because hey, why > shouldn't root be able to access everything... But then it struck me > that that might actually be a good idea for all those reasons. root's > tools don't expect that the namespace they are traversing is > _completely_ controlled by a user.
Exactly.
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