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Date: Sun, 1 Oct 2023 21:13:03 +0200
From: Solar Designer <>
Subject: "Linux Kernel security demistified"


Greg KH gave a talk entitled "Linux Kernel security demistified" at
Kernel Recipes 2023 (10th Edition) on September 26 in Paris, France.

Thank you, Greg!

Here are the slides:

Video: (4:09:30 to 5:00:40)

My summary and thoughts:

The talk is primarily about the Linux kernel security process.  It
starts with a mention of the European Union Cyber Resiliance Act (CRA)
and how it is problematic for Open Source, a topic we haven't yet
touched here on oss-security, but many relevant organizations have, e.g.
here's Apache Foundation's summary from July:

(If we want to discuss in here, which I'm not sure of, please start a
separate thread for this sub-topic, do not just reply to this one.)

A relevant point is that governments and companies want "early security
notices".  Another is that "early notice lists are leaks and should be
considered public."  A way out of this mess is not to play the game.
This adds to the many technical reasons also given in the talk not to
document security fixes as such, not to assign CVEs, and to recommend
usage of upstream stable kernel trees over "enterprise" distro kernels.

There are relevant questions and answers after the talk, including on
(not) notifying the linux-distros list.  I can see how this fits in with
not playing the game to avoid the slippery slope.  As usual, it remains
up to issue reporters to choose who or what lists they notify.

I wonder whether the kernel documentation could, however, be encouraging
rather than discouraging (as it currently is) about issue reporters
themselves contacting linux-distros after a fix is ready.  I wonder if a
patch like that would be accepted?

In an answer, Greg blames linux-distros for "blackmailing" the kernel
security team by our requirement to make everything including exploits
(if posted to the list) public, a requirement we had already lifted:

and by having a (low) maximum embargo time (14 days).  Google P0's 90
days is mentioned as adequate maximum (with typical times until a Linux
kernel fix is ready being way shorter than that).  Yet a slide says "No
embargoes longer than 7 days" without a mention this is 7 days after fix
is ready (I assume an inadvertent omission).

I was/am of course thinking whether we should possibly make the
linux-distros embargo times consistent with s@...'s as an exception.
We had already granted the Linux kernel and curl exceptions allowing
semi-public fixes, then relaxed the rules on exploit posting, and now
this remains the final inconsistency.  We could address it, too.

However, if a reason to stop notifying linux-distros is avoiding a
precedent of s@k.o providing early security notices to any other group,
then us adjusting the rules would be counter-productive as it'd remove
the needed excuse.  Of course, I don't expect any reply to this - it's
just an impression/insight I got from the talk, and it's kind of fine.
I understand the kernel security team works under pressure as-is and I
don't want to add to that.

There's also an upcoming Webinar:

> Demystifying the Linux Kernel Security Process
> October 3, 2023 | 07:00 AM PDT (UTC-7)
> Join an interactive, complimentary Mentorship Session exploring
> Demystifying the Linux Kernel Security Process with Greg Kroah-Hartman,
> Kernel Maintainer & Fellow, The Linux Foundation
> There is a lot of misunderstanding about how the Linux kernel deals with
> security vulnerabilities.  This talk will go into how the Linux kernel
> security team works, how changes are propagated out to the public, and
> how users must take advantage of these changes in order to have a secure
> system.

(Announcements of upcoming events generally don't fit oss-security, but
including this along with material from the prior event is acceptable.)


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