From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.alien8.de (mail.alien8.de [65.109.113.108]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BDAAC30AAA6 for ; Wed, 3 Dec 2025 17:36:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=65.109.113.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764783386; cv=none; b=SpMCJl5naTzLW/9pqOb5Efk2funDogBQ0VdtloT8Wld0vU3Z/K1bqiY9QWRa8ZWVVndSaNhhrkj7ECiRBkWsnsKvSWjDrqFEvuIuksltLAaHKk7SGUztDze6cjUxtaX7JVpG8bx0UzttlsHtfLiIGp4XHi17DUwhzWtMY5cYCkU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764783386; c=relaxed/simple; bh=XUUGMW08TcnFNpi367JvjWanDDHhntL46T1R26X6F8Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=matgBVmQ4g3RRlQx6hDYBtf9JWVL2mUyh/CQCKeEY63oPqRm3XOcYRTEyibmiGjlyx07jOxikfEh7DRQAlvIDDw2tc753+g2Yc8uLO67/pvenDprZMbqBtY285NWrP99V2kJmvj6yTrB9UycOwWI3bT6AIeGcgnhtV4Z41W5HEM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=alien8.de; spf=pass smtp.mailfrom=alien8.de; dkim=pass (4096-bit key) header.d=alien8.de header.i=@alien8.de header.b=hl6P93HF; arc=none smtp.client-ip=65.109.113.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=alien8.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=alien8.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (4096-bit key) header.d=alien8.de header.i=@alien8.de header.b="hl6P93HF" Received: from localhost (localhost.localdomain [127.0.0.1]) by mail.alien8.de (SuperMail on ZX Spectrum 128k) with ESMTP id 1D92740E0250; Wed, 3 Dec 2025 17:36:21 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at mail.alien8.de Authentication-Results: mail.alien8.de (amavisd-new); dkim=pass (4096-bit key) header.d=alien8.de Received: from mail.alien8.de ([127.0.0.1]) by localhost (mail.alien8.de [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 8zGlPQ-u_ES9; Wed, 3 Dec 2025 17:36:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=alien8; t=1764783375; bh=9am7AJwn2c3469AnteM7forW1EBVQrm0tBu36szZJaw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hl6P93HFg5ZuY645tm8sa83gMARTcsp/a/rWFCEj0HvahLQ/j0VVW/QoIAWIUjpY3 fuL89udCtAkHXPSqRtFiJg9m7lWg4HK/DPgwfZ5Br/YOW8fhe/vvHwr6vkgqR2qNuS CFcCeszVRT7HXJZU7I4G12rANWknYvXTQKrVdwhgNpPRlzwVXtmi0qaeIWY+kQu9yy kRT0EWV/lgPqQMXri2kAa2T9cc6m2ooAQVlDIH5/lQNu7JT/VliyLHNr4TiePlR5cF yZlL+S6pNtS9rcjAv2k68RvcLwufarrKopk5hVfFl4ayk7cDorNyjd6jmomicihx2b UDDIdb+yrYfKFZvm9hKTxTjTsvMcxlC6MO3XliYqxG+QBRNjk19/PxZrZycpyYvGDO IFWRAfXhCBaR8o7+kb/ZkvclV12+58eRW4pfTgfFQmCwpra9zK8AgHyO0Z8i6im2T9 vgn0brk/qVniwbSi/+opWHm7vh+m5jsp/hmEYi9FlozxUVo6t/Lo3m2R+yGz9x05dr sCqbsYUHiBtpShKolG279hqVOYhOz9WQKMu2WeLHNpPRXsq4BJEsPDeTCuSGmT0tRC f/8u44lHmSHs3zJZQa3/r+reX/JLf+8IDG24ryW1s4RYnXR3zl0iYQf2zOSzm9rADk MfbxMBZ0OiVyyElwr+Cvxld8= Received: from zn.tnic (pd953063a.dip0.t-ipconnect.de [217.83.6.58]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature ECDSA (P-256) server-digest SHA256) (No client certificate requested) by mail.alien8.de (SuperMail on ZX Spectrum 128k) with UTF8SMTPSA id 0CF6F40E01C5; Wed, 3 Dec 2025 17:36:02 +0000 (UTC) Date: Wed, 3 Dec 2025 18:35:56 +0100 From: Borislav Petkov To: "Kaplan, David" Cc: Brendan Jackman , Thomas Gleixner , Peter Zijlstra , Josh Poimboeuf , Pawan Gupta , Ingo Molnar , Dave Hansen , "x86@kernel.org" , "H . Peter Anvin" , Alexander Graf , Boris Ostrovsky , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH 07/56] x86/bugs: Reset spectre_v2_user mitigations Message-ID: <20251203173556.GDaTB0_K4MR4CorGMT@fat_crate.local> References: <20251013143444.3999-8-david.kaplan@amd.com> <20251126112320.GNaSbjKPpKWNRLDLwP@fat_crate.local> <20251203123125.GAaTAtneKj5v1OaqtS@fat_crate.local> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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