linux-kernel - Re: Kdump with signed images

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Message-ID: <9db4437f-7dbb-427f-968c-685500b89877@email.android.com>
Date:	Tue, 06 Nov 2012 00:01:56 +0100
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Vivek Goyal <vgoyal@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Matthew Garrett <mjg@...hat.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Khalid Aziz <khalid@...ehiking.org>, kexec@...ts.infradead.org,
	horms@...ge.net.au, Dave Young <dyoung@...hat.com>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Dmitry Kasatkin <dmitry.kasatkin@...el.com>,
	Roberto Sassu <roberto.sassu@...ito.it>,
	Kees Cook <keescook@...omium.org>,
	Peter Jones <pjones@...hat.com>
Subject: Re: Kdump with signed images

Yes, it is unlikely you can pare thibgs down more than klibc.

Vivek Goyal <vgoyal@...hat.com> wrote:

>On Mon, Nov 05, 2012 at 11:44:48AM -0800, Eric W. Biederman wrote:
>> Vivek Goyal <vgoyal@...hat.com> writes:
>> 
>> > On Fri, Nov 02, 2012 at 02:32:48PM -0700, Eric W. Biederman wrote:
>> >> 
>> >> It needs to be checked but /sbin/kexec should not use any
>functions that
>> >> trigger nss switch.  No user or password or host name lookup
>should be
>> >> happening.
>> >
>> > I also think that we don't call routines which trigger nss switch
>but
>> > be probably can't rely on that as somebody might introduce it in
>> > future. So we need more robust mechanism to prevent it than just
>code
>> > inspection.
>> 
>> The fact that we shouldn't use those routines is enough to let us
>> walk down a path where they are not used.  Either with a static glibc
>> linked told to use no nss modules (--enable-static-nss ?), or with
>> another more restricted libc.
>
>Is there anything wrong with using uClibc? Trying to link again
>customized glibc (with --enable-static-nss) sounds just extra work for
>build environments. Are there know restricted libc or we need to create
>one with passing more compile time options to libc.
>
>Instead of doing more work in an attempt to create restricted libc,
>it might be easier to just link against any already available
>restricted library.
>
>Thanks
>Vivek

-- 
Sent from my mobile phone. Please excuse brevity and lack of formatting.
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