linux-kernel - Re: [RFC PATCH 0/9] livepatch: consistency model

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: <alpine.LNX.2.00.1502131520390.2423@pobox.suse.cz>
Date:	Fri, 13 Feb 2015 15:22:15 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
cc:	Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/9] livepatch: consistency model

On Fri, 13 Feb 2015, Josh Poimboeuf wrote:

> > How about we take a slightly different aproach -- put a probe (or ftrace) 
> > on __switch_to() during a klp transition period, and examine stacktraces 
> > for tasks that are just about to start running from there?
> > 
> > The only tasks that would not be covered by this would be purely CPU-bound 
> > tasks that never schedule. But we are likely in trouble with those anyway, 
> > because odds are that non-rescheduling CPU-bound tasks are also 
> > RT-priority tasks running on isolated CPUs, which we will fail to handle 
> > anyway.
> > 
> > I think Masami used similar trick in his kpatch-without-stopmachine 
> > aproach.
> 
> Yeah, that's definitely an option, though I'm really not too crazy about
> it.  Hooking into the scheduler is kind of scary and disruptive.  

This is basically about running a stack checking for ->next before 
switching to it, i.e. read-only operation (admittedly inducing some 
latency, but that's the same with locking the runqueue). And only when in 
transition phase.

> We'd also have to wake up all the sleeping processes.

Yes, I don't think there is a way around that.

Thanks,

-- 
Jiri Kosina
SUSE Labs
--
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/