linux-kernel - Re: [PATCH v5 1/2] x86/speculation: apply IBPB more strictly to avoid cross-process data leak

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Date:   Mon, 22 Oct 2018 01:32:04 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Pavel Machek <pavel@....cz>
cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "Schaufler, Casey" <casey.schaufler@...el.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v5 1/2] x86/speculation: apply IBPB more strictly to
 avoid cross-process data leak

On Sun, 21 Oct 2018, Pavel Machek wrote:

> Imagine JIT running evil code (flash, javascript). JIT will prevent evil 
> code from doing ptrace() (or maybe there is syscall filter in effect or 
> something like that), but if evil code can poison branch buffers and do 
> timings, security problem stays.

JITs sort of remove the traditional unix security domain boundary between 
mutually (un)trusted code (processess and threads), that's a more general 
problem, yes.

> Do we need prctl(I_DONT_RUN_EVIL_CODE)?

That's basically the level of fine-graining Tim's followup patchset 
(that's currently being discussed) is eventually going to achieve.

Thanks,

-- 
Jiri Kosina
SUSE Labs