linux-kernel - Re: [PATCH v10 0/11] seccomp: add thread sync ability

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Date:	Wed, 16 Jul 2014 14:27:38 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Kees Cook <keescook@...omium.org>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexei Starovoitov <ast@...mgrid.com>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Will Drewry <wad@...omium.org>,
	Julien Tinnes <jln@...omium.org>,
	David Drysdale <drysdale@...gle.com>,
	Linux API <linux-api@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v10 0/11] seccomp: add thread sync ability

On Wed, Jul 16, 2014 at 2:23 PM, Kees Cook <keescook@...omium.org> wrote:
> On Wed, Jul 16, 2014 at 12:45 PM, Andy Lutomirski <luto@...capital.net> wrote:
>> In seccomp_prepare_user_filter, would it make sense to return -EINVAL
>> if !user_filter?  That will make it slightly more pleasant to
>> implement TSYNC-without-change if anyone ever wants it.  (This isn't
>> really necessary -- it's just slightly more polite.)
>
> I can't do this since EFAULT is already used to detect seccomp
> capabilities from userspace.

Aha.  In that case, can you (separately) send a prctl.2 manpage patch
documenting that?  Also, I'm pretty sure you can get away with doing
this for seccomp(2) -- EINVAL and ENOSYS are easily distinguishable,
but the current behavior is IMO also fine if documented.

--Andy
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