Date: Wed, 17 Nov 2010 11:03:21 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Dan Rosenberg <drosenberg@vsecurity.com>, linux-kernel@vger.kernel.org,
        security@kernel.org, stable@kernel.org
Subject: Re: [PATCH] Restrict unprivileged access to kernel syslog
Message-ID: <20101117100321.GB1574@ucw.cz>
References: <1289273338.6287.128.camel@dan>
 <20101109120649.62b487e8@lxorguk.ukuu.org.uk>
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On Tue 2010-11-09 12:06:49, Alan Cox wrote:
> On Mon, 08 Nov 2010 22:28:58 -0500
> Dan Rosenberg <drosenberg@vsecurity.com> wrote:
> 
> > The kernel syslog contains debugging information that is often useful
> > during exploitation of other vulnerabilities, such as kernel heap
> > addresses.  Rather than futilely attempt to sanitize hundreds (or
> > thousands) of printk statements and simultaneously cripple useful
> > debugging functionality, it is far simpler to create an option that
> > prevents unprivileged users from reading the syslog.
> 
> Except for anything that appears on the screen - which is remotely
> readable via the screen access APIs. Looks sane to me (pointless but
> sane) and the checks match the ones needed to redirect the console so you
> need CAP_SYS_ADMIN either way.

/dev/vcsa is only protected by filesystem permissions IIRC.

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