linux-kernel - Re: Regression in v4.19.106 breaking waking up of readers of /proc/kmsg and /dev/kmsg

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: <20200229033253.GA212847@google.com>
Date:   Sat, 29 Feb 2020 12:32:53 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     Petr Mladek <pmladek@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Lech Perczak <l.perczak@...lintechnologies.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Krzysztof Drobiński 
        <k.drobinski@...lintechnologies.com>,
        Pawel Lenkow <p.lenkow@...lintechnologies.com>,
        John Ogness <john.ogness@...utronix.de>,
        Tejun Heo <tj@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: Regression in v4.19.106 breaking waking up of readers of
 /proc/kmsg and /dev/kmsg

On (20/02/28 15:53), Theodore Y. Ts'o wrote:
> > So, I would still prefer to _revert_ the commit 15341b1dd409749f
> > ("char/random: silence a lockdep splat with printk()"). It calmed
> > down lockdep report. The real life danger is dubious. The warning
> > is printed early when the system is running on single CPU where
> > it could not race.
> 
> I'm wondering now if we should revert this commit before 5.6 comes out
> (it landed in 5.6-rc1).  "Is much less likely to happen given the
> other random initialization patches" is not the same as "guaranteed
> not to happen".
> 
> What do folks think?

Well, my 5 cents, there is nothing that prevents "too-early"
printk_deferred() calls in the future. From that POV I'd probably
prefer to "forbid" printk_deffered() to touch per-CPU deferred
machinery until it's not "too early" anymore. Similar to what we
do in printk_safe::queue_flush_work().

	-ss