linux-kernel - Re: What can OpenVZ do?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1234909849.4816.9.camel@nimitz>
Date:	Tue, 17 Feb 2009 14:30:49 -0800
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-api@...r.kernel.org, containers@...ts.linux-foundation.org,
	hpa@...or.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	viro@...iv.linux.org.uk, mpm@...enic.com, tglx@...utronix.de,
	torvalds@...ux-foundation.org, xemul@...nvz.org,
	Nathan Lynch <nathanl@...tin.ibm.com>
Subject: Re: What can OpenVZ do?

On Tue, 2009-02-17 at 23:23 +0100, Ingo Molnar wrote:
> * Dave Hansen <dave@...ux.vnet.ibm.com> wrote:
> > On Fri, 2009-02-13 at 11:53 +0100, Ingo Molnar wrote:
> > > In any case, by designing checkpointing to reuse the existing LSM
> > > callbacks, we'd hit multiple birds with the same stone. (One of
> > > which is the constant complaints about the runtime costs of the LSM
> > > callbacks - with checkpointing we get an independent, non-security
> > > user of the facility which is a nice touch.)
> > 
> > There's a fundamental problem with using LSM that I'm seeing 
> > now that I look at using it for file descriptors.  The LSM 
> > hooks are there to say, "No, you can't do this" and abort 
> > whatever kernel operation was going on.  That's good for 
> > detecting when we do something that's "bad" for checkpointing.
> > 
> > *But* it completely falls on its face when we want to find out 
> > when we are doing things that are *good*.  For instance, let's 
> > say that we open a network socket.  The LSM hook sees it and 
> > marks us as uncheckpointable.  What about when we close it?  
> > We've become checkpointable again.  But, there's no LSM hook 
> > for the close side because we don't currently have a need for 
> > it.
> 
> Uncheckpointable should be a one-way flag anyway. We want this 
> to become usable, so uncheckpointable functionality should be as 
> painful as possible, to make sure it's getting fixed ...

Again, as these patches stand, we don't support checkpointing when
non-simple files are opened.  Basically, if a open()/lseek() pair won't
get you back where you were, we don't deal with them.

init does non-checkpointable things.  If the flag is a one-way trip,
we'll never be able to checkpoint because we'll always inherit init's !
checkpointable flag.  

To fix this, we could start working on making sure we can checkpoint
init, but that's practically worthless.

-- Dave

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/