From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763011AbZEGXAf (ORCPT ); Thu, 7 May 2009 19:00:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754301AbZEGXA0 (ORCPT ); Thu, 7 May 2009 19:00:26 -0400 Received: from mail-ew0-f176.google.com ([209.85.219.176]:35040 "EHLO mail-ew0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752791AbZEGXAZ (ORCPT ); Thu, 7 May 2009 19:00:25 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:content-transfer-encoding :in-reply-to:user-agent; b=q7dDHoeCA7XiSLPZFo07NXvca3QUxaQ7VssDgYaEdXCVZ7p8PQ6aN02oSgAW1Lus16 f4gKG3PuP0j7cm6jdEI0UaSlTGqLAk46+KeB0EkHRfYo90IR2lwvyrAio1OobP88F8cX c21kLShpazkXiyIzZZVpVbPy614K8Y2OkZ56Y= Date: Fri, 8 May 2009 01:00:22 +0200 From: Frederic Weisbecker To: Adam Langley Cc: Ingo Molnar , Andrew Morton , Tom Zanussi , Li Zefan , Steven Rostedt , linux-kernel@vger.kernel.org, markus@google.com Subject: Re: [RFC 1/1] seccomp: Add bitmask of allowed system calls. Message-ID: <20090507230021.GC6472@nowhere> References: <396556a20805301217k293e5718h6bbf02b234897235@europa> <20090507221447.GE28770@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 07, 2009 at 03:34:58PM -0700, Adam Langley wrote: > > That assessment is incorrect, there's no difference between safety > > here really. > > > > LSM cannot magically inspect user-space memory either when multiple > > threads may access it. The point would be to define filters for > > system call _arguments_, which are inherently thread-local and safe. > > If I hook security_operations.socket_connect, I can validate the struct > sockaddr after the final copy_from_user. However, since the sockaddr lives in > userspace memory, if I try and validate it from ftrace SYSCALL_ENTER, I can't > know that it won't change before sys_connect reads it again. > > Because of that, there are system calls which an LSM hook can safely accept > that an ftrace hook cannot. However, as you point out, any arguments passed in > registers are inheriently safe and these may be sufficiently powerful. > > > There are two problems with the bitmap scheme, which i also > > suggested in a previous thread but then found it to be lacking: > > > > 1) enumeration: you define a bitmap. That will be problematic > >   between compat and native 64-bit (both have different syscall > >   vectors). > > I /think/ it works out, but I've been bitten before with subtle 32/64 bit > compat issues and accept that it's a bit ugly. > > > 2) flexibility. It's an on/off selection per syscall. With the > >   filter we have on, off, or filtered. That's a _whole_ lot more > >   flexible. > > Absolutely. > > Is there a git tree that I can pull this parsing code from? > (git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git > maybe?). I can patch in the seccomp-on-ftrace work and try building the > filtering on top of that. I'll see how it turns out anyway. Hi, The most uptodate one is: git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git on the tracing/filters topic. See kernel/trace/trace_events_filter.c You might want to reuse some current syscall tracing facility. An automated resolution table is built on bootime, you can look at the end of arch/x86/kernel/ftrace.c This table links each syscalls nr to the matching attribute entry of syscall in which you can find: - parameters names - parameters types - syscall name You can look at the hooks in include/linux/syscall.h: The sections inside #ifdef CONFIG_FTRACE_SYSCALLS Well, it's a bit insane to read, so you can also look at include/trace/syscall.h and kernel/trace/trace_syscalls.c and see how it is used and how it could be reused. Thanks, Frederic.