linux-kernel - Re: [PATCH v3 2/3] x86/ldt: Make modify

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 24 Jul 2015 09:24:51 +0200
From:	Willy Tarreau <w@....eu>
To:	Kees Cook <keescook@...omium.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"security@...nel.org" <security@...nel.org>,
	X86 ML <x86@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Sasha Levin <sasha.levin@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Jan Beulich <jbeulich@...e.com>,
	xen-devel <xen-devel@...ts.xen.org>
Subject: Re: [PATCH v3 2/3] x86/ldt: Make modify_ldt optional

On Thu, Jul 23, 2015 at 05:09:21PM -0700, Kees Cook wrote:
> > All this to say that probably only a handful of tricky syscalls would
> > need an on/off switch but clearly not all of them at all, so I'd rather
> > add a few entries just for the relevant ones, mainly to fix compatibility
> > issues and nothing more. Eg: what's the point of disabling exit(), wait(),
> > kill(), fork() or getpid()... It would only increase the difficulty to
> > sort out bug reports.
> >
> > Just my opinion,
> 
> Well, I would really like to have something like this around so that I
> can trivially globally disable syscalls when they have security risks.

I understand, but while maybe it could make sense to have the option on
any linux-specific syscall, having it on the standard, portable ones
will be useless as disabling them will break most applications.

> My hack[1] to disable kexec_load, for example, was terrible while I
> waited for a kernel that supported the disable_kexec_load sysctl.

This typically is one linux-specific syscall which no regular application
would rely on and which can come with side effects. I think there are not
*that* many, none of them is performance-critical, and they'd rather be
dealt with one at a time.

> [1] https://outflux.net/blog/archives/2013/12/10/live-patching-the-kernel/

Thanks, that (and the linked articles) was an interesting read.

Willy

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/