linux-kernel - Re: Proposal: CAP_PAYLOAD to reduce Meltdown and Spectre mitigation costs

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: <20180107122918.GE2404@thunk.org>
Date:   Sun, 7 Jan 2018 07:29:18 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Avi Kivity <avi@...lladb.com>
Cc:     Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Proposal: CAP_PAYLOAD to reduce Meltdown and Spectre mitigation
 costs

On Sun, Jan 07, 2018 at 11:16:28AM +0200, Avi Kivity wrote:
> I think capabilities will work just as well with cgroups. The container
> manager will set CAP_PAYLOAD to payload containers; and if those run an init
> system or a container manager themselves, they'll drop CAP_PAYLOAD for all
> process/sub-containers but their payloads.

The reason why cgroups are better is Spectre can be used to steal
information from within the same privilege level --- e.g., you could
use Javascript to steal a user's Coindesk credentials or Lastpass
data, which is going to be *way* more lucrative than trying to mine
cryptocurrency in the sly in a user's browser.  :-)

As a result, you probably want Spectre mitigations to be enabled in a
root process --- which means capabilities aren't the right answer.

Regards,

						- Ted