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 6C269C433EF for ; Mon, 6 Dec 2021 15:43:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1391130AbhLFPpK (ORCPT ); Mon, 6 Dec 2021 10:45:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59374 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1388170AbhLFPcX (ORCPT ); Mon, 6 Dec 2021 10:32:23 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 872D2C08E856; Mon, 6 Dec 2021 07:19:27 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 50471B81135; Mon, 6 Dec 2021 15:19:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7C7F3C341C1; Mon, 6 Dec 2021 15:19:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1638803965; bh=rhQ6gw2N4GendxGyO6hG8ndGQ19HAKkm+QVk7bFiWG4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=l5DPpk9RX95DJpmynOdqDLExYCGEMTL2B0eLGRI3g5HoeRVpjhRrAhp4UoJ23CObh V+VLdDwZpFwThehRgLdgfviE4xv5jZxprBoQGXNaOBP0xSuhHiWhi4vaCNOZoDfJvm 2dQELSnRyiBHP9V1hI5rJd75N0otaVZ0wCBnhZpM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lai Jiangshan , Borislav Petkov , Sasha Levin Subject: [PATCH 5.10 110/130] x86/entry: Add a fence for kernel entry SWAPGS in paranoid_entry() Date: Mon, 6 Dec 2021 15:57:07 +0100 Message-Id: <20211206145603.437518528@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211206145559.607158688@linuxfoundation.org> References: <20211206145559.607158688@linuxfoundation.org> User-Agent: quilt/0.66 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: Lai Jiangshan [ Upstream commit c07e45553da1808aa802e9f0ffa8108cfeaf7a17 ] Commit 18ec54fdd6d18 ("x86/speculation: Prepare entry code for Spectre v1 swapgs mitigations") added FENCE_SWAPGS_{KERNEL|USER}_ENTRY for conditional SWAPGS. In paranoid_entry(), it uses only FENCE_SWAPGS_KERNEL_ENTRY for both branches. This is because the fence is required for both cases since the CR3 write is conditional even when PTI is enabled. But 96b2371413e8f ("x86/entry/64: Switch CR3 before SWAPGS in paranoid entry") changed the order of SWAPGS and the CR3 write. And it missed the needed FENCE_SWAPGS_KERNEL_ENTRY for the user gsbase case. Add it back by changing the branches so that FENCE_SWAPGS_KERNEL_ENTRY can cover both branches. [ bp: Massage, fix typos, remove obsolete comment while at it. ] Fixes: 96b2371413e8f ("x86/entry/64: Switch CR3 before SWAPGS in paranoid entry") Signed-off-by: Lai Jiangshan Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20211126101209.8613-2-jiangshanlai@gmail.com Signed-off-by: Sasha Levin --- arch/x86/entry/entry_64.S | 16 +++++----------- 1 file changed, 5 insertions(+), 11 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 166554a109aeb..a24ce5905ab82 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -936,6 +936,7 @@ SYM_CODE_START_LOCAL(paranoid_entry) .Lparanoid_entry_checkgs: /* EBX = 1 -> kernel GSBASE active, no restore required */ movl $1, %ebx + /* * The kernel-enforced convention is a negative GSBASE indicates * a kernel value. No SWAPGS needed on entry and exit. @@ -943,21 +944,14 @@ SYM_CODE_START_LOCAL(paranoid_entry) movl $MSR_GS_BASE, %ecx rdmsr testl %edx, %edx - jns .Lparanoid_entry_swapgs - ret + js .Lparanoid_kernel_gsbase -.Lparanoid_entry_swapgs: + /* EBX = 0 -> SWAPGS required on exit */ + xorl %ebx, %ebx swapgs +.Lparanoid_kernel_gsbase: - /* - * The above SAVE_AND_SWITCH_TO_KERNEL_CR3 macro doesn't do an - * unconditional CR3 write, even in the PTI case. So do an lfence - * to prevent GS speculation, regardless of whether PTI is enabled. - */ FENCE_SWAPGS_KERNEL_ENTRY - - /* EBX = 0 -> SWAPGS required on exit */ - xorl %ebx, %ebx ret SYM_CODE_END(paranoid_entry) -- 2.33.0