linux-kernel - Re: [PATCH v2] printk: Add kernel parameter to disable writes to /dev/kmsg

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Message-ID: <20160426111213.GS3448@twins.programming.kicks-ass.net>
Date:	Tue, 26 Apr 2016 13:12:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH v2] printk: Add kernel parameter to disable writes to
 /dev/kmsg

On Mon, Apr 25, 2016 at 12:54:37PM -0700, Greg Kroah-Hartman wrote:
> On Mon, Apr 25, 2016 at 09:24:35PM +0200, Peter Zijlstra wrote:
> > On Mon, Apr 25, 2016 at 12:18:15PM -0700, Greg Kroah-Hartman wrote:
> > > On Mon, Apr 25, 2016 at 09:06:51PM +0200, Peter Zijlstra wrote:
> > > > On Mon, Apr 25, 2016 at 02:56:06PM -0400, Steven Rostedt wrote:
> > > > > +static bool __read_mostly devkmsg_disabled;
> > > > > +static int __init disable_devkmsg(char *str)
> > > > > +{
> > > > > +	devkmsg_disabled = true;
> > > > > +	return 0;
> > > > > +}
> > > > > +__setup("printk.disable_kmsg_write", disable_devkmsg);
> > > > 
> > > > Again, please default enable and use an easier name to toggle this.
> > > > Userspace flooding this with junk is really insane.
> > > 
> > > If you default enable, you break working systems today that want to log
> > > stuff through this interface, sorry.
> > 
> > Oh, you mean those 'working' systems that livelocked my box because I
> > had console to serial enabled which could not keep up with the endless
> > flood of shite?
> > 
> > This systemd exposure has seriously eroded your sanity.
> 
> See Andrew's message, this was added because of klibc :)

The initial feature, yes. But systemd ran with it and made it a problem
(as per usual).