linux-kernel - Re: [RFC PATCH v1.9 12/14] livepatch: create per-task 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]

Date:	Mon, 4 Apr 2016 20:27:59 +0200
From:	Vojtech Pavlik <vojtech@...e.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Miroslav Benes <mbenes@...e.cz>, Jiri Kosina <jikos@...nel.org>,
	Jessica Yu <jeyu@...hat.com>, linux-kernel@...r.kernel.org,
	live-patching@...r.kernel.org
Subject: Re: [RFC PATCH v1.9 12/14] livepatch: create per-task consistency
 model

On Mon, Apr 04, 2016 at 01:21:38PM -0500, Josh Poimboeuf wrote:

> Hm, can you explain why it should be copied from the parent?
> 
> I'm thinking the above code is correct for today, but it should still be
> changed to be more future-proof.
> 
> Here's my thinking:
> 
> A forked task starts out with no stack, so if I understand correctly, it
> can safely start out in the goal universe, regardless of which universe
> its parent belongs to.
> 
> However, the current ret_from_fork code is a mess, and Andy Lutomirski
> has mentioned that he would like to give newly forked tasks a proper
> stack such that instead of jumping to ret_from_fork, they would just
> return from schedule().  In that case, it would no longer be safe to
> start the new task in the goal universe because it could be "sleeping"
> on a to-be-patched function.
> 
> So for proper future proofing, newly forked tasks should be started in
> the initial universe (rather than starting in the goal universe or
> inheriting the parent's universe).  They can then be transitioned over
> to the goal universe like any other task.  How does that sound?

How could a newly forked task start in the old universe if its parent
has already been migrated? Any context it inherits will already be from
the new universe.

-- 
Vojtech Pavlik
Director SuSE Labs