linux-kernel - Re: [PATCH v6 00/10] Retpoline: Avoid speculative indirect calls in kernel

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Date:   Mon, 8 Jan 2018 08:13:09 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Paul Turner <pjt@...gle.com>
Cc:     David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kees Cook <keescook@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Jiri Kosina <jikos@...nel.org>,
        One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Subject: Re: [PATCH v6 00/10] Retpoline: Avoid speculative indirect calls in
 kernel

On Mon, Jan 08, 2018 at 02:42:13AM -0800, Paul Turner wrote:
> 
> kernel->kernel independent of SMEP:
> While much harder to coordinate, facilities such as eBPF potentially
> allow exploitable return targets to be created.
> Generally speaking (particularly if eBPF has been disabled) the risk
> is _much_ lower here, since we can only return into kernel execution
> that was already occurring on another thread (which could e.g. likely
> be attacked there directly independent of RSB poisoning.)

we can remove bpf interpreter without losing features:
https://patchwork.ozlabs.org/patch/856694/
Ironically JIT is more secure than interpreter.