linux-kernel - Re: [PATCH v2 5/8] x86/speculation: Add basic support for IBPB

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1516560862.9814.47.camel@infradead.org>
Date:   Sun, 21 Jan 2018 18:54:22 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     arjan@...ux.intel.com, tglx@...utronix.de, karahmed@...zon.de,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        tim.c.chen@...ux.intel.com, peterz@...radead.org,
        pbonzini@...hat.com, ak@...ux.intel.com,
        torvalds@...ux-foundation.org, gregkh@...ux-foundation.org
Subject: Re: [PATCH v2 5/8] x86/speculation: Add basic support for IBPB

On Sun, 2018-01-21 at 19:06 +0100, Borislav Petkov wrote:
> 
> > switch to using ALTERNATIVES instead of static_cpu_has]
> 
> Why?
> 
>         if (static_cpu_has(X86_FEATURE_IBPB))
>                 wrmsr(MSR_IA32_PRED_CMD, PRED_CMD_IBPB, 0);
> 
> It can't get any more readable than this. Why even f*ck with
> alternatives?

Because we're backporting this to every stable kernel under the sun,
and they don't already require asm-goto. Peter does have a dozen or so
objtool patches to protect us against the missed GCC optimisation which
would make it vulnerable via a conditional branch, but we'll do that
*after* the basic backportable implementation using ALTERNATIVE goes
in.
Download attachment "smime.p7s" of type "application/x-pkcs7-signature" (5213 bytes)