linux-kernel - [PATCH printk v1 0/1] Allow unsafe ->write

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-next>] [day] [month] [year] [list]

Message-Id: <20250912121852.2666874-1-john.ogness@linutronix.de>
Date: Fri, 12 Sep 2025 14:24:51 +0206
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Breno Leitao <leitao@...ian.org>,
	Mike Galbraith <efault@....de>,
	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH printk v1 0/1] Allow unsafe ->write_atomic() for panic

Hi,

An effort is underway to update netconsole to support nbcon [0].
Currently it is not known exactly how a safe ->write_atomic()
callback for netconsole could be implemented. However, without
->write_atomic() implemented, there is guaranteed to be _no_
panic output.

We decided to allow unsafe ->write_atomic() implementations to
be used only as a last resort at the end of panic. This should
allow netconsole to be updated to support nbcon and still
provide panic output in "typical panic" situations.

I considered extending the feature to also allow such consoles
to print using their ->write_thread() callback whenever it is
known to be a sleepable context. However, this started to get
quite complex. We can revisit this extended feature if it is
determined that it is necessary.

John Ogness

[0] https://lore.kernel.org/lkml/b2qps3uywhmjaym4mht2wpxul4yqtuuayeoq4iv4k3zf5wdgh3@tocu6c7mj4lt

John Ogness (1):
  printk: nbcon: Allow unsafe write_atomic() for panic

 include/linux/console.h |  3 +++
 kernel/printk/nbcon.c   | 17 ++++++++++++++---
 kernel/printk/printk.c  | 23 ++++++++++++++++-------
 3 files changed, 33 insertions(+), 10 deletions(-)


base-commit: 37dbd4203b42c10b76d55471bb866900f99d6bc1
-- 
2.39.5