linux-kernel - Re: printk: Add kernel parameter to disable writes to /dev/kmsg

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Message-ID: <20160426184458.GB8162@amd>
Date:	Tue, 26 Apr 2016 20:44:58 +0200
From:	Pavel Machek <pavel@....cz>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: printk: Add kernel parameter to disable writes to /dev/kmsg

On Mon 2016-04-25 13:06:29, Steven Rostedt wrote:
> Over the weekend my server was acting funny. The display wasn't working
> well, and I assumed that a driver was going bad. I went to look at the
> kernel dmesg, but the buffer only had the following over and over:
> 
> [226062.401405] systemd-logind[3511]: Removed session 4168.
> [226063.381051] systemd-logind[3511]: Removed session 4169.

systemd has root. I'm not sure additional parameter to fight it is
good idea. What's next? systemd evolves a way to override kernel
parameters? :-)

> I simply propose a way to let us kernel developers keep user space from
> interfering, by adding a new kernel command line parameter that will
> disable writing to /dev/kmsg. Any attempt to open the file in write
> mode will return a -EPERM error.

chmod 400 /dev/kmsg? With udev, it should be possible to make it persistent...

									Pavel

-- 
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