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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BBC5AC55186 for ; Wed, 22 Apr 2020 10:01:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8F6252077D for ; Wed, 22 Apr 2020 10:01:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587549700; bh=X7tkqdwf/gdG2Xy9w+W21yJY2bhLGPbO3mQXETkAvbU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=t8ceBCzvhT4clIpjLXwJioxYGDRZNEo5G6/keaan852g3pd8YLzRDZxuV+OhC7u/c qLFfaZRumiJdTEJd14VEMd8jdhdLOuOEfTxjVjv2NpSoWTdbaDwcRExFdyqejlheWR FCgXrQAAQmgCSdZAX5xk5pAXqRJzx0F641DZF6b8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726848AbgDVKBj (ORCPT ); Wed, 22 Apr 2020 06:01:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:50084 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726832AbgDVKBe (ORCPT ); Wed, 22 Apr 2020 06:01:34 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9A0902076C; Wed, 22 Apr 2020 10:01:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587549694; bh=X7tkqdwf/gdG2Xy9w+W21yJY2bhLGPbO3mQXETkAvbU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VFJDJWfbWPzJNUMgOzT1/CmsCGiFjgBZtCpmjVLXGWpP1MphyseHlazlLySW33w+w 52VpZeg/pVk1nVCnLkYt/ID2+6z4KZfDctu5pljgpmgEa97/z5NE6iUMTf9KddCLse //sUiUtQMCfw04VZZfn4DMmFPziDrm0xQ/+RF4YU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Borislav Petkov Subject: [PATCH 4.4 069/100] x86/mitigations: Clear CPU buffers on the SYSCALL fast path Date: Wed, 22 Apr 2020 11:56:39 +0200 Message-Id: <20200422095035.514854526@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200422095022.476101261@linuxfoundation.org> References: <20200422095022.476101261@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Borislav Petkov The fast SYSCALL exit path returns with SYSRET to userspace after verifying that there's no pending work. MDS mitigation mandates that CPU buffers must be cleared on transition from kernel to userspace so do that here too. Signed-off-by: Borislav Petkov Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/entry_64.S | 2 ++ arch/x86/include/asm/spec-ctrl.h | 2 ++ arch/x86/kernel/cpu/bugs.c | 5 +++++ 3 files changed, 9 insertions(+) --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -218,6 +218,8 @@ entry_SYSCALL_64_fastpath: testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) jnz int_ret_from_sys_call_irqs_off /* Go to the slow path */ + call mds_user_clear_buffers + movq RIP(%rsp), %rcx movq EFLAGS(%rsp), %r11 RESTORE_C_REGS_EXCEPT_RCX_R11 --- a/arch/x86/include/asm/spec-ctrl.h +++ b/arch/x86/include/asm/spec-ctrl.h @@ -85,4 +85,6 @@ static inline void speculative_store_byp extern void speculation_ctrl_update(unsigned long tif); extern void speculation_ctrl_update_current(void); +extern void mds_user_clear_buffers(void); + #endif --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -263,6 +263,11 @@ static int __init mds_cmdline(char *str) } early_param("mds", mds_cmdline); +void mds_user_clear_buffers(void) +{ + mds_user_clear_cpu_buffers(); +} + #undef pr_fmt #define pr_fmt(fmt) "TAA: " fmt