linux-kernel - Re: [PATCH v2 1/2] x86/speculation: Allow enabling STIBP with legacy IBRS

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: <Y/UbqiHQ2/aczPzg@kroah.com>
Date:   Tue, 21 Feb 2023 20:29:46 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     KP Singh <kpsingh@...nel.org>
Cc:     linux-kernel@...r.kernel.org, pjt@...gle.com, evn@...gle.com,
        jpoimboe@...nel.org, tglx@...utronix.de, x86@...nel.org,
        hpa@...or.com, peterz@...radead.org,
        pawan.kumar.gupta@...ux.intel.com, kim.phillips@....com,
        alexandre.chartre@...cle.com, daniel.sneddon@...ux.intel.com,
        corbet@....net, bp@...e.de, linyujun809@...wei.com,
        jmattson@...gle.com,
        José Oliveira <joseloliveira11@...il.com>,
        Rodrigo Branco <rodrigo@...nelhacking.com>,
        Alexandra Sandulescu <aesa@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] x86/speculation: Allow enabling STIBP with legacy
 IBRS

On Tue, Feb 21, 2023 at 07:49:07PM +0100, KP Singh wrote:
> Setting the IBRS bit implicitly enables STIBP to protect against
> cross-thread branch target injection. With enhanced IBRS, the bit it set
> once and is not cleared again. However, on CPUs with just legacy IBRS,
> IBRS bit set on user -> kernel and cleared on kernel -> user (a.k.a
> KERNEL_IBRS). Clearing this bit also disables the implicitly enabled
> STIBP, thus requiring some form of cross-thread protection in userspace.
> 
> Enable STIBP, either opt-in via prctl or seccomp, or always on depending
> on the choice of mitigation selected via spectre_v2_user.
> 
> Reported-by: José Oliveira <joseloliveira11@...il.com>
> Reported-by: Rodrigo Branco <rodrigo@...nelhacking.com>
> Reviewed-by: Alexandra Sandulescu <aesa@...gle.com>
> Fixes: 7c693f54c873 ("x86/speculation: Add spectre_v2=ibrs option to support Kernel IBRS")
> Cc: stable@...r.kernel.org
> Signed-off-by: KP Singh <kpsingh@...nel.org>
> ---
>  arch/x86/kernel/cpu/bugs.c | 33 ++++++++++++++++++++++-----------
>  1 file changed, 22 insertions(+), 11 deletions(-)

Why isn't patch 2/2 for stable as well?

thanks,

greg k-h