linux-hardening - [PATCH 0/3] module: Add compile-time check for embedded NUL characters

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20251008033844.work.801-kees@kernel.org>
Date: Tue,  7 Oct 2025 20:59:32 -0700
From: Kees Cook <kees@...nel.org>
To: Luis Chamberlain <mcgrof@...nel.org>
Cc: Kees Cook <kees@...nel.org>,
	Malcolm Priestley <tvboxspy@...il.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Hans Verkuil <hverkuil@...nel.org>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Petr Pavlu <petr.pavlu@...e.com>,
	Daniel Gomez <da.gomez@...nel.org>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org,
	linux-modules@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH 0/3] module: Add compile-time check for embedded NUL characters

Hi,

A long time ago we had an issue with embedded NUL bytes in MODULE_INFO
strings[1]. While this stands out pretty strongly when you look at the
code, and we can't do anything about a binary module that just plain lies,
we never actually implemented the trivial compile-time check needed to
detect it.

Add this check (and fix 2 instances of needless trailing semicolons that
this change exposed).

Note that these patches were produced as part of another LLM exercise.
This time I wanted to try "what happens if I ask an LLM to go read
a specific LWN article and write a patch based on a discussion?" It
pretty effortlessly chose and implemented a suggested solution, tested
the change, and fixed new build warnings in the process.

Since this was a relatively short session, here's an overview of the
prompts involved as I guided it through a clean change and tried to see
how it would reason about static_assert vs _Static_assert. (It wanted
to use what was most common, not what was the current style -- we may
want to update the comment above the static_assert macro to suggest
using _Static_assert directly these days...)

  I want to fix a weakness in the module info strings. Read about it
  here: https://lwn.net/Articles/82305/

  Since it's only "info" that we need to check, can you reduce the checks
  to just that instead of all the other stuff?

  I think the change to the comment is redundent, and that should be
  in a commit log instead. Let's just keep the change to the static assert.

  Is "static_assert" the idiomatic way to use a static assert in this
  code base? I've seen _Static_assert used sometimes.

  What's the difference between the two?

  Does Linux use C11 by default now?

  Then let's not use the wrapper any more.

  Do an "allmodconfig all -s" build to verify this works for all modules
  in the kernel.

Thanks!

-Kees

[1] https://lwn.net/Articles/82305/

Kees Cook (3):
  media: dvb-usb-v2: lmedm04: Fix firmware macro definitions
  media: radio: si470x: Fix DRIVER_AUTHOR macro definition
  module: Add compile-time check for embedded NUL characters

 include/linux/moduleparam.h                   |  3 +++
 drivers/media/radio/si470x/radio-si470x-i2c.c |  2 +-
 drivers/media/usb/dvb-usb-v2/lmedm04.c        | 12 ++++++------
 3 files changed, 10 insertions(+), 7 deletions(-)

-- 
2.34.1