linux-kernel - Re: [PATCH] bcachefs: no console_lock in bch2_print_string_as

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: <87o775cpmj.fsf@jogness.linutronix.de>
Date: Wed, 10 Jul 2024 16:07:40 +0206
From: John Ogness <john.ogness@...utronix.de>
To: Daniel Vetter <daniel.vetter@...ll.ch>, DRI Development
 <dri-devel@...ts.freedesktop.org>, LKML <linux-kernel@...r.kernel.org>
Cc: Intel Graphics Development <intel-gfx@...ts.freedesktop.org>, Daniel
 Vetter <daniel.vetter@...ll.ch>,
 syzbot+6cebc1af246fe020a2f0@...kaller.appspotmail.com, Daniel Vetter
 <daniel.vetter@...el.com>, stable@...r.kernel.org, Kent Overstreet
 <kent.overstreet@...ux.dev>, Brian Foster <bfoster@...hat.com>,
 linux-bcachefs@...r.kernel.org, Petr Mladek <pmladek@...e.com>, Steven
 Rostedt <rostedt@...dmis.org>, Sergey Senozhatsky
 <senozhatsky@...omium.org>
Subject: Re: [PATCH] bcachefs: no console_lock in bch2_print_string_as_lines

On 2024-07-10, Daniel Vetter <daniel.vetter@...ll.ch> wrote:
> console_lock is the outermost subsystem lock for a lot of subsystems,
> which means get/put_user must nest within. Which means it cannot be
> acquired somewhere deeply nested in other locks, and most definitely
> not while holding fs locks potentially needed to resolve faults.
>
> console_trylock is the best we can do here. But John pointed out on a
> previous version that this is futile:
>
> "Using the console lock here at all is wrong. The console lock does not
> prevent other CPUs from calling printk() and inserting lines in between.
>
> "There is no way to guarantee a contiguous ringbuffer block using
> multiple printk() calls.
>
> "The console_lock usage should be removed."
>
> https://lore.kernel.org/lkml/87frsh33xp.fsf@jogness.linutronix.de/
>
> Do that.
>
> Reported-by: syzbot+6cebc1af246fe020a2f0@...kaller.appspotmail.com
> References: https://lore.kernel.org/dri-devel/00000000000026c1ff061cd0de12@google.com/
> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
> Fixes: a8f354284304 ("bcachefs: bch2_print_string_as_lines()")

Reviewed-by: John Ogness <john.ogness@...utronix.de>