From mboxrd@z Thu Jan 1 00:00:00 1970 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 41770EE49A0 for ; Mon, 21 Aug 2023 19:58:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229932AbjHUT6h (ORCPT ); Mon, 21 Aug 2023 15:58:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59598 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229922AbjHUT6h (ORCPT ); Mon, 21 Aug 2023 15:58:37 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C69E11C for ; Mon, 21 Aug 2023 12:58:35 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 32C97646CC for ; Mon, 21 Aug 2023 19:58:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 427D8C433C8; Mon, 21 Aug 2023 19:58:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692647914; bh=m34dcTHPMSS6n4BVRcRs2osf6gaO0M3cDkAVsJO2cvM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=v7h3zvzlvtmRHeeetiqNK4kMssdSmTiDcvmtS516fcQ0N5MwDd1lSaW9beNB/ucqr VhGH4RgQadpPISrLflfzBF8RNPd7mqqvfFNgHXhDCbKGxU7AsMSBCqC0lSCjkYXTjo +tAsga7oNoYGwb8GDCxAtEyEu7Guki7ew8RIXMtw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Borislav Petkov (AMD)" , stable@kernel.org Subject: [PATCH 6.1 183/194] x86/CPU/AMD: Fix the DIV(0) initial fix attempt Date: Mon, 21 Aug 2023 21:42:42 +0200 Message-ID: <20230821194130.750180601@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230821194122.695845670@linuxfoundation.org> References: <20230821194122.695845670@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Borislav Petkov (AMD) commit f58d6fbcb7c848b7f2469be339bc571f2e9d245b upstream. Initially, it was thought that doing an innocuous division in the #DE handler would take care to prevent any leaking of old data from the divider but by the time the fault is raised, the speculation has already advanced too far and such data could already have been used by younger operations. Therefore, do the innocuous division on every exit to userspace so that userspace doesn't see any potentially old data from integer divisions in kernel space. Do the same before VMRUN too, to protect host data from leaking into the guest too. Fixes: 77245f1c3c64 ("x86/CPU/AMD: Do not leak quotient data after a division by 0") Signed-off-by: Borislav Petkov (AMD) Cc: Link: https://lore.kernel.org/r/20230811213824.10025-1-bp@alien8.de Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/entry-common.h | 1 + arch/x86/kernel/cpu/amd.c | 1 + arch/x86/kernel/traps.c | 2 -- arch/x86/kvm/svm/svm.c | 2 ++ 4 files changed, 4 insertions(+), 2 deletions(-) --- a/arch/x86/include/asm/entry-common.h +++ b/arch/x86/include/asm/entry-common.h @@ -92,6 +92,7 @@ static inline void arch_exit_to_user_mod static __always_inline void arch_exit_to_user_mode(void) { mds_user_clear_cpu_buffers(); + amd_clear_divider(); } #define arch_exit_to_user_mode arch_exit_to_user_mode --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -1295,3 +1295,4 @@ void noinstr amd_clear_divider(void) asm volatile(ALTERNATIVE("", "div %2\n\t", X86_BUG_DIV0) :: "a" (0), "d" (0), "r" (1)); } +EXPORT_SYMBOL_GPL(amd_clear_divider); --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -206,8 +206,6 @@ DEFINE_IDTENTRY(exc_divide_error) { do_error_trap(regs, 0, "divide error", X86_TRAP_DE, SIGFPE, FPE_INTDIV, error_get_trap_addr(regs)); - - amd_clear_divider(); } DEFINE_IDTENTRY(exc_overflow) --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3947,6 +3947,8 @@ static noinstr void svm_vcpu_enter_exit( guest_state_enter_irqoff(); + amd_clear_divider(); + if (sev_es_guest(vcpu->kvm)) __svm_sev_es_vcpu_run(svm, spec_ctrl_intercepted); else