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 61288C3DA6F for ; Thu, 24 Aug 2023 17:23:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239405AbjHXRWr (ORCPT ); Thu, 24 Aug 2023 13:22:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242872AbjHXRWS (ORCPT ); Thu, 24 Aug 2023 13:22:18 -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 B81D51BCA for ; Thu, 24 Aug 2023 10:22:12 -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 98FF3675B1 for ; Thu, 24 Aug 2023 17:22:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ACE57C433C8; Thu, 24 Aug 2023 17:22:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692897732; bh=4sL7G+p3DcFUon8bDiJn5oy8c/f1m24p8oRECnbEW/g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0oHc2TX0C99CYprhoCy5gunvHJmcvBNRkv8TejFnCReKjkTpkfTdojPC0XscPn66D oxEcgf8H2TmRgXCc3rfXebwsObEsAz+Vu6NkSWP4PfG03rTJyD4TYkgK2i/HCoZroN +HFz2/Pzb07jMoNsD8ElmZJNuIwUfBf1emijchEs= 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 5.10 131/135] x86/CPU/AMD: Fix the DIV(0) initial fix attempt Date: Thu, 24 Aug 2023 19:10:03 +0200 Message-ID: <20230824170622.924407979@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230824170617.074557800@linuxfoundation.org> References: <20230824170617.074557800@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ 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 | 1 + 4 files changed, 3 insertions(+), 2 deletions(-) --- a/arch/x86/include/asm/entry-common.h +++ b/arch/x86/include/asm/entry-common.h @@ -78,6 +78,7 @@ 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 @@ -1332,3 +1332,4 @@ 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 @@ -198,8 +198,6 @@ 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 @@ -3376,6 +3376,7 @@ static void svm_flush_tlb_gva(struct kvm static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu) { + amd_clear_divider(); } static inline void sync_cr8_to_lapic(struct kvm_vcpu *vcpu)