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From: Greg KH <gregkh@linuxfoundation.org>
To: Matthew Garrett <matthew.garrett@nebula.com>
Cc: Kees Cook <keescook@chromium.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
	"hpa@zytor.com" <hpa@zytor.com>
Subject: Re: [PATCH V3 08/11] kexec: Disable at runtime if the kernel enforces module loading restrictions
Date: Sun, 8 Sep 2013 09:39:26 -0700	[thread overview]
Message-ID: <20130908163926.GA19665@kroah.com> (raw)
In-Reply-To: <1378657487.2300.10.camel@x230>

On Sun, Sep 08, 2013 at 04:24:47PM +0000, Matthew Garrett wrote:
> On Sun, 2013-09-08 at 09:18 -0700, Greg KH wrote:
> 
> > I want both, but I don't need signed kexec support because I want to use
> > kexec for a program that I "know" is correct because I validated the
> > disk image it was on before I mounted it.  We already have other ways to
> > "verify" things without having to add individual verification of
> > specific pieces.
> 
> The kernel has no way to know that your kexec payload is coming from a
> verified image. It'll just as happily take something from an unverified
> image. If you've ensured that there's no way an attacker can call
> kexec_load() on an unverified image, then you don't need signed modules.

But I want, for other reasons (i.e. safety in layers), signed kernel
modules.  I also might actually want some debugfs files in some random
driver (like this series removes).

The point is that having a "lockdown" mode is good, I'm not disagreeing
there.  Just don't force it on people if they don't want it.  Allow them
to pick "lock everything down", or "I want signed modules", or "I don't
want kexec".

Don't lump all of this together such that people can not make that
choice between different things, because some people (i.e. me
specifically), do want them.

Heck, look at Red Hat.  They have been shipping signed kernel modules
for _years_ and yet they do not disable kexec.  Have they been "doing it
wrong" all of this time?   Perhaps people want signed modules just for
support reasons, not "security" reasons.

Don't take away those options.

thanks,

greg k-h

WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
To: Matthew Garrett
	<matthew.garrett-05XSO3Yj/JvQT0dZR+AlfA@public.gmane.org>
Cc: Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org"
	<hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH V3 08/11] kexec: Disable at runtime if the kernel enforces module loading restrictions
Date: Sun, 8 Sep 2013 09:39:26 -0700	[thread overview]
Message-ID: <20130908163926.GA19665@kroah.com> (raw)
In-Reply-To: <1378657487.2300.10.camel@x230>

On Sun, Sep 08, 2013 at 04:24:47PM +0000, Matthew Garrett wrote:
> On Sun, 2013-09-08 at 09:18 -0700, Greg KH wrote:
> 
> > I want both, but I don't need signed kexec support because I want to use
> > kexec for a program that I "know" is correct because I validated the
> > disk image it was on before I mounted it.  We already have other ways to
> > "verify" things without having to add individual verification of
> > specific pieces.
> 
> The kernel has no way to know that your kexec payload is coming from a
> verified image. It'll just as happily take something from an unverified
> image. If you've ensured that there's no way an attacker can call
> kexec_load() on an unverified image, then you don't need signed modules.

But I want, for other reasons (i.e. safety in layers), signed kernel
modules.  I also might actually want some debugfs files in some random
driver (like this series removes).

The point is that having a "lockdown" mode is good, I'm not disagreeing
there.  Just don't force it on people if they don't want it.  Allow them
to pick "lock everything down", or "I want signed modules", or "I don't
want kexec".

Don't lump all of this together such that people can not make that
choice between different things, because some people (i.e. me
specifically), do want them.

Heck, look at Red Hat.  They have been shipping signed kernel modules
for _years_ and yet they do not disable kexec.  Have they been "doing it
wrong" all of this time?   Perhaps people want signed modules just for
support reasons, not "security" reasons.

Don't take away those options.

thanks,

greg k-h

  reply	other threads:[~2013-09-08 16:36 UTC|newest]

Thread overview: 108+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-03 23:50 Matthew Garrett
2013-09-03 23:50 ` (unknown), Matthew Garrett
2013-09-03 23:50 ` [PATCH V3 01/11] Add secure_modules() call Matthew Garrett
2013-09-04  0:45   ` James Morris
2013-09-04  0:45     ` James Morris
2013-09-05  2:14   ` joeyli
2013-09-05  2:14     ` joeyli
2013-09-03 23:50 ` [PATCH V3 02/11] PCI: Lock down BAR access when module security is enabled Matthew Garrett
2013-09-04  0:45   ` James Morris
2013-09-04  0:45     ` James Morris
2013-09-04 16:57   ` David Woodhouse
2013-09-04 16:57     ` David Woodhouse
2013-09-04 17:04     ` Matthew Garrett
2013-09-04 17:04       ` Matthew Garrett
2013-09-04 18:58       ` David Woodhouse
2013-09-04 19:01         ` Matthew Garrett
2013-09-04 19:01           ` Matthew Garrett
2013-09-04 19:31           ` David Woodhouse
2013-09-04 19:31             ` David Woodhouse
2013-09-03 23:50 ` [PATCH V3 03/11] x86: Lock down IO port " Matthew Garrett
2013-09-04  0:45   ` James Morris
2013-09-05  3:52   ` H. Peter Anvin
2013-09-05  3:52     ` H. Peter Anvin
2013-09-05  3:58     ` Matthew Garrett
2013-09-05  3:58       ` Matthew Garrett
2013-09-05 15:36       ` H. Peter Anvin
2013-09-05 15:36         ` H. Peter Anvin
2013-09-03 23:50 ` [PATCH V3 04/11] ACPI: Limit access to custom_method Matthew Garrett
2013-09-04  0:46   ` James Morris
2013-09-04  0:46     ` James Morris
2013-09-03 23:50 ` [PATCH V3 05/11] asus-wmi: Restrict debugfs interface when module loading is restricted Matthew Garrett
2013-09-04  0:46   ` James Morris
2013-09-04  0:46     ` James Morris
2013-09-03 23:50 ` [PATCH V3 06/11] Restrict /dev/mem and /dev/kmem " Matthew Garrett
2013-09-04  0:47   ` James Morris
2013-09-04  0:47     ` James Morris
2013-09-03 23:50 ` [PATCH V3 07/11] acpi: Ignore acpi_rsdp kernel parameter " Matthew Garrett
2013-09-03 23:50   ` Matthew Garrett
2013-09-03 23:50 ` [PATCH V3 08/11] kexec: Disable at runtime if the kernel enforces module loading restrictions Matthew Garrett
2013-09-04  0:48   ` James Morris
2013-09-04  0:48     ` James Morris
2013-09-04 20:09   ` jerry.hoemann
2013-09-04 20:09     ` jerry.hoemann-VXdhtT5mjnY
2013-09-04 20:12     ` Matthew Garrett
2013-09-04 20:12       ` Matthew Garrett
2013-09-04 20:12       ` Matthew Garrett
2013-09-04 20:14     ` Josh Boyer
2013-09-04 20:14       ` Josh Boyer
2013-09-04 20:14       ` Josh Boyer
2013-09-08  6:40   ` Greg KH
2013-09-08  6:40     ` Greg KH
2013-09-08  6:44     ` Matthew Garrett
2013-09-08  6:44       ` Matthew Garrett
2013-09-08  7:24       ` Greg KH
2013-09-08  7:24         ` Greg KH
2013-09-08 14:40         ` Matthew Garrett
2013-09-08 14:40           ` Matthew Garrett
2013-09-08 15:51         ` Kees Cook
2013-09-08 15:51           ` Kees Cook
2013-09-08 16:18           ` Greg KH
2013-09-08 16:18             ` Greg KH
2013-09-08 16:24             ` Matthew Garrett
2013-09-08 16:24               ` Matthew Garrett
2013-09-08 16:39               ` Greg KH [this message]
2013-09-08 16:39                 ` Greg KH
2013-09-08 16:59                 ` Matthew Garrett
2013-09-08 16:59                   ` Matthew Garrett
2013-09-08 17:22                   ` Greg KH
2013-09-08 17:22                     ` Greg KH
2013-09-08 17:25                     ` Matthew Garrett
2013-09-08 17:25                       ` Matthew Garrett
2013-09-08 17:11           ` James Bottomley
2013-09-08 17:11             ` James Bottomley
2013-09-08 17:15             ` Matthew Garrett
2013-09-08 17:15               ` Matthew Garrett
2013-09-08 17:22               ` James Bottomley
2013-09-08 17:22                 ` James Bottomley
2013-09-08 17:27                 ` Matthew Garrett
2013-09-08 17:27                   ` Matthew Garrett
2013-09-08 17:32                   ` James Bottomley
2013-09-08 17:32                     ` James Bottomley
2013-09-08 17:38                     ` Matthew Garrett
2013-09-08 17:38                       ` Matthew Garrett
2013-09-03 23:50 ` [PATCH V3 09/11] uswsusp: Disable when module loading is restricted Matthew Garrett
2013-09-04  0:48   ` James Morris
2013-09-04  0:48     ` James Morris
2013-09-05  3:20   ` joeyli
2013-09-05  3:20     ` joeyli
2013-09-03 23:50 ` [PATCH V3 10/11] x86: Restrict MSR access " Matthew Garrett
2013-09-04  0:49   ` James Morris
2013-09-04  0:49     ` James Morris
2013-09-03 23:50 ` [PATCH V3 11/11] Add option to automatically enforce module signatures when in Secure Boot mode Matthew Garrett
2013-09-03 23:50   ` Matthew Garrett
2013-09-04  1:42   ` James Morris
2013-09-04  1:42     ` James Morris
2013-09-04  1:42     ` Matthew Garrett
2013-09-04  1:42       ` Matthew Garrett
2013-09-05  3:13   ` joeyli
2013-09-05  8:24   ` joeyli
2013-09-05  8:24     ` joeyli
2013-09-05 10:16   ` Matt Fleming
2013-09-05 10:16     ` Matt Fleming
2013-09-05 12:54     ` Matthew Garrett
2013-09-05 12:54       ` Matthew Garrett
2013-09-04 15:53 ` Kees Cook
2013-09-04 15:53   ` Re: Kees Cook
2013-09-04 16:05   ` Re: Josh Boyer
2013-09-04 16:05     ` Re: Josh Boyer

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