linux-kernel - Re: Out of tree module using LSM

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Date:	Thu, 29 Nov 2007 13:38:28 -0500
From:	Jon Masters <jcm@...hat.com>
To:	Justin Banks <justinb@...bone.com>
Cc:	Ray Lee <ray-lk@...rabbit.org>, Greg KH <greg@...ah.com>,
	Jan Engelhardt <jengelh@...putergmbh.de>,
	Valdis.Kletnieks@...edu, Christoph Hellwig <hch@...radead.org>,
	Al Viro <viro@....linux.org.uk>,
	Casey Schaufler <casey@...aufler-ca.com>,
	"Tvrtko A. Ursulin" <tvrtko.ursulin@...hos.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Out of tree module using LSM


On Thu, 2007-11-29 at 11:19 -0700, Justin Banks wrote:
> Ray Lee wrote
> > On Nov 29, 2007 9:45 AM, Greg KH <greg@...ah.com> wrote:
> > > > Perhaps if you looked at this outside of a file-server scenario, the
> > > > problem would be clearer? Anti-malware companies want to check
> > > > anything written to disk on a system, either at write time or blocking
> > > > the open/mmap. That means proactively protecting email programs with
> > > > known vulnerabilities that have yet to be patched, web browsers
> > > > writing and reading their caches, an Apache instance running WebDAV,
> > > > the list goes on. And these are on desktop systems, with no attached
> > > > file/network server.
> > >
> > > Ok, if they want to check on every open/mmap then just hook in glibc to
> > > do this.  Especially as they want to run userspace code at this point in
> > > time.
> > 
> > Doesn't help statically linked binaries, or anything else that bypases glibc.
> 
> Or NFS servers for that matter, either.

Right. I threw all of these examples out there and was given the
impression that a one-size fits all "solution" is needed. And to be
honest, I can understand that desire.

I don't want to fall into any "snake oil" traps, because I know the
reality is that there are holes in any solution. The only way
to /really/ be sure of file integrity is to mark every user-visible
pagecache page read only, trap on every single write, and re-scan the
entirety of the file at that point. And even more silliness.

A compromise is therefore called for. I will go shut up and go talk to
these guys and see if I can hook up a public discussion around a set of
requirements. Preferably some code too, but at least a requirements doc.

Thanks,

Jon.


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