Messages in this thread | | | Date | Thu, 8 Jul 2010 08:20:59 -0700 | From | Greg KH <> | Subject | Re: BUG: Securityfs and bind mounts (2.6.34) |
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On Thu, Jul 08, 2010 at 03:55:01PM +0100, Tvrtko Ursulin wrote: > On Thursday 08 Jul 2010 15:43:17 Greg KH wrote: > > On Thu, Jul 08, 2010 at 11:12:41AM +0100, Tvrtko Ursulin wrote: > > > Hi guys, > > > > > > If I overlay a file in securityfs using mount --bind with a file from > > > a regular filesystem, should I be allowed to rmmod the module which > > > registered the overlaid securityfs file? > > > > Why would you want to overlay securityfs in the first place? > > For testing, more precisely faking some data exposed in securityfs module in > order to provoke userspace reaction. It was convenient to leave the majority > of real data and just overlay one file. > > > And you might be able to rmmod the module, but I didn't think that > > security modules were able to be unloaded anymore. > > Perhaps it is not a security module in the way you think about it, just a > module which happens to register some directories and files under securityfs.
Ick, don't do that then :)
> > > I was able to do that, then I > > > unmounted the bind mount, and then when attempting to unmount > > > securityfs hit a BUG at > > > fs/dcache.c:676 (see below). It would have made more sense to first > > > umount the overlay file and then remove the module which registered > > > with securityfs, nevertheless should kernel crash in this case? > > > > Probably not, but then again, you did something that you shouldn't have, > > so perhaps it is telling you not to do such a thing in the future :) > > :) Well I do not know, but, it kind of smelled like a bug in the vfs/mount > handling/securityfs area so I thought to let experts know. I _think_ I did > nothing that much wrong. Just used the exposed API (securityfs_remove) and > some bind mount shuffling from userspace.
securitfs just uses libfs underneath it, and really doesn't have any bindings for module ownerships, so I wouldn't recommend doing what you just did.
thanks,
greg k-h
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