linux-kernel - Re: [PATCH v3 10/10] x86-64: Add CONFIG_UNSAFE

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Date:	Wed, 01 Jun 2011 13:35:32 -0400
From:	Valdis.Kletnieks@...edu
To:	Andy Lutomirski <luto@....EDU>
Cc:	Ingo Molnar <mingo@...e.hu>, x86@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Jesper Juhl <jj@...osbits.net>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Jan Beulich <JBeulich@...ell.com>,
	richard -rw- weinberger <richard.weinberger@...il.com>,
	Mikael Pettersson <mikpe@...uu.se>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH v3 10/10] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule

On Tue, 31 May 2011 09:16:04 EDT, Andy Lutomirski said:

> +What:	CONFIG_UNSAFE_VSYSCALLS (x86_64)

Wow. I went nuts trying to find where this was because I couldn't find it in
Linus's tree I pulled a little while ago, before I realized you added it in patch 8
and deprecated it in patch 10.

Speaking of which:

+	  On a system with recent enough glibc (probably 2.14 or
+	  newer) and no static binaries, you can say N without a
+	  performance penalty to improve security

So I checked my laptop (Fedora 16 Rawhide), and found a bunch of static binaries. The ones
that look like people may care:

# file /sbin/* | grep statically
/sbin/grub:                ELF 32-bit LSB executable, Intel 80386, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.18, stripped
/sbin/insmod.static:       ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.32, stripped
/sbin/ldconfig:            ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.32, stripped
/sbin/sln:                 ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.32, stripped

Might be a challenge to get rid of them though.  Unless we don't care anymore
about "use a statically linked ldconfig to fix a corrupted ls.so.cache" and
"reboot from a rescue disk" the only choice.  I think the insmod.static ends up
getting used in initrds to get the root filesystem mounted, we may care about
that as well.. ;)

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