linux-kernel - Re: [PATCH v2] kmsg: Honor dmesg

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Date:	Wed, 24 Apr 2013 19:44:33 +0200
From:	Kay Sievers <kay@...y.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Josh Boyer <jwboyer@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Eric Paris <eparis@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christian Kujau <lists@...dbynature.de>,
	"# 3.4.x" <stable@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kmsg: Honor dmesg_restrict sysctl on /dev/kmsg

On Tue, Apr 9, 2013 at 6:33 PM, Kees Cook <keescook@...omium.org> wrote:
> On Tue, Apr 9, 2013 at 8:48 AM, Josh Boyer <jwboyer@...hat.com> wrote:
>> The dmesg_restrict sysctl currently covers the syslog method for access
>> dmesg, however /dev/kmsg isn't covered by the same protections.  Most
>> people haven't noticed because util-linux dmesg(1) defaults to using the
>> syslog method for access in older versions.  With util-linux dmesg(1)
>> defaults to reading directly from /dev/kmsg.
>>
>> Fix this by reworking all of the access methods to use the
>> check_syslog_permissions function and adding checks to devkmsg_open and
>> devkmsg_read.
>>
>> This fixes https://bugzilla.redhat.com/show_bug.cgi?id=903192
>>
>> Reported-by: Christian Kujau <lists@...dbynature.de>
>> CC: stable@...r.kernel.org
>> Signed-off-by: Eric Paris <eparis@...hat.com>
>> Signed-off-by: Josh Boyer <jwboyer@...hat.com>
>
> Thanks!
>
> Acked-by: Kees Cook <keescook@...omium.org>

If that's the version currently in Fedora, we just cannot do this.
   https://bugzilla.redhat.com/show_bug.cgi?id=952655

/dev/kmsg is supposed, and was added, to be a sane alternative to
syslog(). It is already used in dmesg(1) which is now broken with this
patch.

The access rules for /dev/kmsg should follow the access rules of
syslog(), and not be any stricter.

Thanks,
Kay
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