linux-kernel - Re: [PATCH RFC 1/2] x86/entry_64: Add a separate unmitigated entry/exit path

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: <20240920072423.65uekxy3a6ueqxyy@desk>
Date: Fri, 20 Sep 2024 00:24:23 -0700
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: Waiman Long <longman@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Kaplan <David.Kaplan@....com>,
	Daniel Sneddon <daniel.sneddon@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org
Subject: Re: [PATCH RFC 1/2] x86/entry_64: Add a separate unmitigated
 entry/exit path

On Fri, Sep 20, 2024 at 02:57:34AM -0400, Waiman Long wrote:
> 
> On 9/19/24 17:52, Pawan Gupta wrote:
> > CPU mitigations are deployed system-wide, but usually not all of the
> > userspace is malicious. Yet, they suffer from the performance impact
> > of the mitigations. This all or nothing approach is due to lack of a
> > way for kernel to know which userspace can be trusted and which cannot.
> > 
> > For scenarios where an admin can decide which processes to trust, an
> > interface to tell the kernel to possibly skip the mitigation would be
> > useful.
> > 
> > In preparation for kernel to be able to selectively apply mitigation
> > per-process add a separate kernel entry/exit path that skips the
> > mitigations.
> > 
> > Originally-by: Josh Poimboeuf <jpoimboe@...nel.org>
> > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
> 
> For the current patch, not all x86 CPU vulnerability mitigations can be
> disabled. Maybe we should list the subset of mitigations that can be
> disabled.

Yes, will update that mitigations that can be bypassed are BHI, VERW,
Retbleed-IBRS, Retbleed-unret and IBPB.

Meltdown, Spectre-v1, eIBRS, GDS, SRBDS, retpoline and rethunk stays
enabled.