linux-kernel - Re: [RFC PATCH 07/56] x86/bugs: Reset spectre_v2

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: <20251203173556.GDaTB0_K4MR4CorGMT@fat_crate.local>
Date: Wed, 3 Dec 2025 18:35:56 +0100
From: Borislav Petkov <bp@...en8.de>
To: "Kaplan, David" <David.Kaplan@....com>
Cc: Brendan Jackman <jackmanb@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>, Alexander Graf <graf@...zon.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 07/56] x86/bugs: Reset spectre_v2_user mitigations

On Wed, Dec 03, 2025 at 05:02:24PM +0000, Kaplan, David wrote:
> We don't know how tasks are using this prctl().  Maybe the task only sets
> PR_SPEC_DISABLE around one specific function call.
> 
> What if a program starts up and queries the kernel and gets PR_SPEC_PRCTL so
> it thinks it can control things.  And then it calls
> PR_SPEC_DISABLE/PR_SPEC_ENABLE around one particular sensitive function.
> 
> And then at some point, it starts getting -EPERM...

Well, we can't have the cake and eat it too - at some point the admin will
override the setting the task did. There's no other way.

> It would be cleaner if userspace never saw errors, but the mitigation were
> just silently applied/not-applied.

As in: if dynamic mitigations are enabled, kernel stops returning EPERM but
simply overrides the mitigation setting and issues a pr_warn_once() that
PR_SPEC_PRCTL doesn't take effect anymore due to system-wide override?

Works for me...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette