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Date: Wed, 6 Nov 2013 22:17:46 +0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Will Drewry <wad@chromium.org>, Eric Paris <eparis@redhat.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Richard Weinberger <richard@nod.at>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        libseccomp-discuss@lists.sourceforge.net,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [libseccomp-discuss] ARM audit, seccomp, etc are broken wrt
	OABI syscalls
Message-ID: <20131106221746.GE16735@n2100.arm.linux.org.uk>
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On Wed, Nov 06, 2013 at 01:26:52PM -0800, Kees Cook wrote:
> On Wed, Nov 6, 2013 at 1:20 PM, Will Drewry <wad@chromium.org> wrote:
> > On Wed, Nov 6, 2013 at 9:51 AM, Russell King - ARM Linux
> > <linux@arm.linux.org.uk> wrote:
> >> On Wed, Nov 06, 2013 at 10:32:31AM -0500, Eric Paris wrote:
> >>> On Tue, 2013-11-05 at 14:36 -0800, Andy Lutomirski wrote:
> >>> > 1. Set a different audit arch for OABI syscalls (e.g.
> >>> > AUDIT_ARCH_ARMOABI).  That is, treat OABI syscall entries the same way
> >>> > that x86_64 treats int 80.
> >>>
> >>> As the audit maintainer, I like #1.  It might break ABI, but the ABI is
> >>> flat wrong now and not maintainable...
> >>
> >> If you read the whole thread, you will see that this corner case is just
> >> not worth the effort to support.  Audit may as well be disabled by
> >> kernel config if any OABI support is enabled.
> >
> > This might be the best move for seccomp too (as Kees suggested).  I'd
> > love to have audit arch visibility, but it's not clear that it's worth
> > any sort of larger changes ...
> >
> > ... like adding a task_thread_info.compat flag that bubbles up to
> > syscall_get_arch(), or if we assume consumers of syscall_get_nr() are
> > broken today (I haven't checked), then it would be possible to at
> > least re-add the 0x900000 bits, if compat, before handing back the
> > system call number but leave the audit arch pieces alone.
> 
> How does this look, for the seccomp part?

Looks correct, thanks.