linux-kernel - Re: [PATCH 0/7] Two-phase seccomp and x86 tracing changes

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Date:	Wed, 16 Jul 2014 14:17:05 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Kees Cook <keescook@...omium.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Will Drewry <wad@...omium.org>,
	James Morris <james.l.morris@...cle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"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>,
	Alexei Starovoitov <ast@...mgrid.com>
Subject: Re: [PATCH 0/7] Two-phase seccomp and x86 tracing changes

On Wed, Jul 16, 2014 at 1:41 PM, Kees Cook <keescook@...omium.org> wrote:
> On Tue, Jul 15, 2014 at 12:32 PM, Andy Lutomirski <luto@...capital.net> wrote:
>> This is both a cleanup and a speedup.  It reduces overhead due to
>> installing a trivial seccomp filter by 87%.  The speedup comes from
>> avoiding the full syscall tracing mechanism for filters that don't
>> return SECCOMP_RET_TRACE.
>>
>> This series works by splitting the seccomp hooks into two phases.
>> The first phase evaluates the filter; it can skip syscalls, allow
>> them, kill the calling task, or pass a u32 to the second phase.  The
>> second phase requires a full tracing context, and it sends ptrace
>> events if necessary.
>>
>> Once this is done, I implemented a similar split for the x86 syscall
>> entry work.  The C callback is invoked in two phases: the first has
>> only a partial frame, and it can request phase 2 processing with a
>> full frame.
>>
>> Finally, I switch the 64-bit system_call code to use the new split
>> entry work.  This is a net deletion of assembly code: it replaces
>> all of the audit entry muck.
>>
>> In the process, I fixed some bugs.
>>
>> If this is acceptable, someone can do the same tweak for the
>> ia32entry and entry_32 code.
>>
>> This passes all seccomp tests that I know of, except for the ones
>> that don't work on current kernels.
>
> After fighting a bit with merging this with the tsync series, I can
> confirm this all behaves nicely on x86_64 and ARM.
>

I'll hold off on v3 until your stuff lands.

--Andy

> -Kees
>
> --
> Kees Cook
> Chrome OS Security



-- 
Andy Lutomirski
AMA Capital Management, LLC
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