From nobody Fri Dec 19 05:01:41 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4AC6DCA0EC3 for ; Tue, 12 Sep 2023 00:57:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232187AbjILA5j (ORCPT ); Mon, 11 Sep 2023 20:57:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44184 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232380AbjILA5e (ORCPT ); Mon, 11 Sep 2023 20:57:34 -0400 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB43310CE for ; Mon, 11 Sep 2023 17:42:12 -0700 (PDT) Received: by mail-qv1-xf49.google.com with SMTP id 6a1803df08f44-655ce9dfae8so29863616d6.3 for ; Mon, 11 Sep 2023 17:42:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1694479243; x=1695084043; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=HCGSGNbrdqSE84CGd9wFzsbbP6gSE2HdtTlTm4rVY0U=; b=o/vOntVQ5dP3h7QmvqIfc37RRLbCMeN/3ttnj3p6lxpphcC4aCudlgFSpR/RNKq352 7rX1RFhx5YDrxvZOBzWCNBWaxaTV0VMccgIFB7W/JFnyAkHPp1QO3pjEmybF+MeEApLj l51+Wqlt/VyqfyYSYi7O5wSOoAyGRPegh+sx8fJZ3heW6CXzn1GtPONe5I8Vo5oq+T4S 2XC3xUhpbzmEcnr1Nx4vKdw6K7Q8oluqb1yweY8zg8uQjKtouUmGAtUxcSdCIJtzBA8d Eqhu+yA6DJ4mhNgTv0Jw1TpJEuqeA3BB40ByY8ZDfloigWqeNY4lgpm+tv5YIs+a5Yn6 88iA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1694479243; x=1695084043; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=HCGSGNbrdqSE84CGd9wFzsbbP6gSE2HdtTlTm4rVY0U=; b=r15qAtYB3D94TI88D+5WivuVtQtAMX6iiSLYpr/o8U56kKyGBW2lh4mcm+qpSnLMDJ wKyU/5JZO44INmb6kaN9ZCvmMib2k4U0oP+BT7HtaQd1TucRcnHDqdZgfVlUpBiptXi9 XvWuApnf56GrlaY4KzdgZRyKD/xVk3tgprIEapaqNEmNs1jrclz4dsa6aPKhONtLlZhy TdMoChCunxJn+ggxi0KJd3vujisfV/ziqfiqeKXXSeWheLDRwzIJ27135yptsh2318js Xv+M+pisH5aE2knMClMX54UAfZv2HZ2WCLcrKLX4eRPSHEtS5N+UNZUPLdTa2+Kd6SjQ AFCQ== X-Gm-Message-State: AOJu0YxVu5Lq5X9tZZjNdYOj1EQpG0J9H5b/iKkvjoKl7SSzhNVmbuTm 27Qnt7837ndiavItLLEyo89xBWHIiFBkrffsfcie6DtYA3t7G17fWjPtuO+RP1SZZI6p9C5HPrV G8qBewA2Vswo1xASNZ/WvuJrBjBY4O6TTLBFRoCc6IosrNRg5STaX3V2j0M2b6whKkIOrU9LXUB 4= X-Google-Smtp-Source: AGHT+IFYKbe4ZG8QfYS8MJV41+9/oOqY4X/pV+pQy3JrXFYSHCgyqNh7IkTzKbnAJdaTt8hDfAk7bJ2LjLy5jA== X-Received: from anticipation.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:4517]) (user=acdunlap job=sendgmr) by 2002:a81:7647:0:b0:57a:e0b:f66 with SMTP id j7-20020a817647000000b0057a0e0b0f66mr283018ywk.7.1694478432944; Mon, 11 Sep 2023 17:27:12 -0700 (PDT) Date: Mon, 11 Sep 2023 17:27:02 -0700 In-Reply-To: <20230912002703.3924521-1-acdunlap@google.com> Mime-Version: 1.0 References: <20230912002703.3924521-1-acdunlap@google.com> X-Mailer: git-send-email 2.42.0.283.g2d96d420d3-goog Message-ID: <20230912002703.3924521-2-acdunlap@google.com> Subject: [PATCH v2 1/2] x86/sev-es: Allow copy_from_kernel_nofault in earlier boot From: Adam Dunlap To: linux-kernel@vger.kernel.org, x86@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , Kim Phillips , Juergen Gross , Ashok Raj , Adam Dunlap , Joerg Roedel Cc: Tom Lendacky , David Hildenbrand , Mike Rapoport , "Kirill A. Shutemov" , Nikunj A Dadhania , Dionna Glaze , Peter Gonda , David Rientjes , Khalid ElMously , Jacob Xu Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Previously, if copy_from_kernel_nofault was called before boot_cpu_data.x86_virt_bits was set up, then it would trigger undefined behavior due to a shift by 64. This ended up causing boot failures in the latest version of ubuntu2204 in the gcp project when using SEV-SNP. Specifically, this function is called during an early #VC handler which is triggered by a cpuid to check if nx is implemented. Fixes: 1aa9aa8ee517 ("x86/sev-es: Setup GHCB-based boot #VC handler") Suggested-by: Dave Hansen Signed-off-by: Adam Dunlap --- arch/x86/mm/maccess.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/x86/mm/maccess.c b/arch/x86/mm/maccess.c index 5a53c2cc169c..6993f026adec 100644 --- a/arch/x86/mm/maccess.c +++ b/arch/x86/mm/maccess.c @@ -9,12 +9,21 @@ bool copy_from_kernel_nofault_allowed(const void *unsafe_= src, size_t size) unsigned long vaddr =3D (unsigned long)unsafe_src; =20 /* - * Range covering the highest possible canonical userspace address - * as well as non-canonical address range. For the canonical range - * we also need to include the userspace guard page. + * Do not allow userspace addresses. This disallows + * normal userspace and the userspace guard page: */ - return vaddr >=3D TASK_SIZE_MAX + PAGE_SIZE && - __is_canonical_address(vaddr, boot_cpu_data.x86_virt_bits); + if (vaddr < TASK_SIZE_MAX + PAGE_SIZE) + return false; + + /* + * Allow everything during early boot before 'x86_virt_bits' + * is initialized. Needed for instruction decoding in early + * exception handlers. + */ + if (!boot_cpu_data.x86_virt_bits) + return true; + + return __is_canonical_address(vaddr, boot_cpu_data.x86_virt_bits); } #else bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size) --=20 2.42.0.283.g2d96d420d3-goog