linux-kernel - Re: RETBleed: WARNING: Spectre v2 mitigation leaves CPU vulnerable to RETBleed attacks, data leaks possible!

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Message-ID: <Ys/kfDk7mVE09N3L@worktop.programming.kicks-ass.net>
Date:   Thu, 14 Jul 2022 11:40:12 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        open list <linux-kernel@...r.kernel.org>,
        X86 ML <x86@...nel.org>, lkft-triage@...ts.linaro.org,
        Borislav Petkov <bp@...e.de>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>
Subject: Re: RETBleed: WARNING: Spectre v2 mitigation leaves CPU vulnerable
 to RETBleed attacks, data leaks possible!

On Thu, Jul 14, 2022 at 11:01:12AM +0200, Greg Kroah-Hartman wrote:
> On Thu, Jul 14, 2022 at 02:15:07PM +0530, Naresh Kamboju wrote:
> > Results from Linaro’s test farm.
> > 
> > We are booting the i386 kernel on an x86 machine.
> > With Spectre V2 patches merged into Linux mainline we have been noticing
> > RETBleed: WARNING: Spectre v2 mitigation leaves CPU vulnerable to
> > RETBleed attacks, data leaks possible!
> 
> That's funny.  I don't think that's a valid combination that should be
> cared about, but I'll leave it to Pawan to comment if it is something
> that is "real" to be concerned for.

Yeah, so far nobody cared to fix 32bit. If someone *realllllly* cares
and wants to put the effort in I suppose I'll review the patches, but
seriously, you shouldn't be running 32bit kernels on Skylake / Zen based
systems, that's just silly.