Messages in this thread | | | From | David Howells <> | Subject | Re: Security issues with local filesystem caching | Date | Fri, 27 Oct 2006 18:34:10 +0100 |
| |
Stephen Smalley <sds@tycho.nsa.gov> wrote:
> > You start the cache by mounting it: > > > > mount -t cachefs /dev/hdx9 /cachefs > > > > Then it's online. However, you might want to check that whoever's calling > > mount has permission to bring a cache online... > > Hmmm...that raises a separate issue - how does SELinux label cachefs > inodes? Does cachefs support xattrs? Other option is to use a mount > context (mount -o context=...) to apply a single context to all inodes > within it.
There are only two inodes publically available through cachefs - the root dir and a file of statistics - and they're both read only. Everything else, for the moment, is strictly internal and unavailable to userspace. In fact, there may not be any other inodes.
> Where exactly is the cachefs code available?
It'll need a little bit of work to make it compilable again; but I can probably get you a copy on Monday. I've been concentrating on CacheFiles.
> I'm also unclear on where you establish the binding between the files > being cached and the cache. What specifies that e.g. a given NFS mount > should be backed to a given cache? We need to be able to control that > relationship too, to establish that the cache is being protected > adequately for the source data.
Yes. I haven't worked that one out yet. Currently it's not a problem as only CacheFiles is available at the moment, and that currently only supports one cache.
But I have an idea that I need to work on to make it possible to associate directories and files with caches (or other useful parameters).
> > (1) Permission to bring a cache online or to take a cache offline. > > At present, this will show up as the usual checking on mount (security > hooks in do_mount and vfs_kern_mount) and on umount (security hook in > do_umount) by SELinux. I'm not sure whether you need anything specific > to the cache.
That doesn't apply to CacheFiles, but okay; we can always add it later if we decide we want it.
David - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |