linux-kernel - Re: [RFC 0/3] extend kexec_file

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: <20160720124649.GB11361@redhat.com>
Date:	Wed, 20 Jul 2016 08:46:49 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Russell King - ARM Linux <linux@...linux.org.uk>
Cc:	Balbir Singh <bsingharora@...il.com>,
	Stewart Smith <stewart@...ux.vnet.ibm.com>, bhe@...hat.com,
	arnd@...db.de, Petr Tesarik <ptesarik@...e.cz>,
	linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
	dyoung@...hat.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 0/3] extend kexec_file_load system call

On Wed, Jul 20, 2016 at 09:35:30AM +0100, Russell King - ARM Linux wrote:
> On Wed, Jul 20, 2016 at 01:45:42PM +1000, Balbir Singh wrote:
> > > IOW, if your kernel forced signature verification, you should not be
> > > able to do sig_enforce=0. If you kernel did not have
> > > CONFIG_MODULE_SIG_FORCE=y, then sig_enforce should be 0 by default anyway
> > > and you are not making it worse using command line.
> > 
> > OK.. I checked and you are right, but that is an example and there are
> > other things like security=, thermal.*, nosmep, nosmap that need auditing
> > for safety and might hurt the system security if used. I still think
> > think that assuming you can pass any command line without breaking security
> > is a broken argument.
> 
> Quite, and you don't need to run code in a privileged environment to do
> any of that.
> 
> It's also not trivial to protect against: new kernels gain new arguments
> which older kernels may not know about.  No matter how much protection
> is built into older kernels, newer kernels can become vulnerable through
> the addition of further arguments.

If a new kernel command line option becomes an issue, new kernel can
block that in secureboot environment. That way it helps kexec
boot as well as regular boot.

Vivek