From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A9A0D1171A for ; Mon, 21 Aug 2023 20:06:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A0A5C433C7; Mon, 21 Aug 2023 20:06:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692648385; bh=6th6LfthIn3IlT5iCdpNktpEtzyPbwTmBGzjyMyhn18=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xkvDwEbdUytxtZdNOCI0KP4XnOuXK0KBoEnLn43+OaETov6Uew1kfir5ok6zhwsw1 i0SIK3Q4fZU83VE+36W4h3ddzas2p6y1H4RZc2C1aSpFVov4fsScZNtDBYQpUIZjNS S8sFQ7AqOzK3ifTEcLIwLtSpFeAoBc1qmzubpb2E= 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 6.4 127/234] x86/CPU/AMD: Fix the DIV(0) initial fix attempt Date: Mon, 21 Aug 2023 21:41:30 +0200 Message-ID: <20230821194134.453983732@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230821194128.754601642@linuxfoundation.org> References: <20230821194128.754601642@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 @@ -1329,3 +1329,4 @@ 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 @@ -4034,6 +4034,8 @@ 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