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 9A4CDC433EF for ; Mon, 6 Dec 2021 15:50:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239885AbhLFPxX (ORCPT ); Mon, 6 Dec 2021 10:53:23 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:49066 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1388469AbhLFPdf (ORCPT ); Mon, 6 Dec 2021 10:33:35 -0500 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 dfw.source.kernel.org (Postfix) with ESMTPS id 0987361322; Mon, 6 Dec 2021 15:30:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5DD2C34900; Mon, 6 Dec 2021 15:30:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1638804604; bh=wL4tWySXBrPzJT5fG9ckppc3JBbRbiWt60uRzrLiJp8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DDRfTYoQdPhO5x6/mhuh1r+ltWx9rV2OOpu/kSrVGLwepYv5fWxZ8v8rTsgoG9bpI GPWXguR47fM6J/6KhXH6vkLUYhFtHiINyk0W3H1XhD1dFGuJTACpoUHHYoN8SszLLy J7ukdK5XGGyKPi7U0GkC6cTHECS0nMzYmB6a2MHs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lai Jiangshan , Borislav Petkov , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 5.15 174/207] x86/entry: Use the correct fence macro after swapgs in kernel CR3 Date: Mon, 6 Dec 2021 15:57:08 +0100 Message-Id: <20211206145616.287986461@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211206145610.172203682@linuxfoundation.org> References: <20211206145610.172203682@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: linux-kernel@vger.kernel.org From: Lai Jiangshan [ Upstream commit 1367afaa2ee90d1c956dfc224e199fcb3ff3f8cc ] The commit c75890700455 ("x86/entry/64: Remove unneeded kernel CR3 switching") removed a CR3 write in the faulting path of load_gs_index(). But the path's FENCE_SWAPGS_USER_ENTRY has no fence operation if PTI is enabled, see spectre_v1_select_mitigation(). Rather, it depended on the serializing CR3 write of SWITCH_TO_KERNEL_CR3 and since it got removed, add a FENCE_SWAPGS_KERNEL_ENTRY call to make sure speculation is blocked. [ bp: Massage commit message and comment. ] Fixes: c75890700455 ("x86/entry/64: Remove unneeded kernel CR3 switching") Signed-off-by: Lai Jiangshan Signed-off-by: Borislav Petkov Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20211126101209.8613-3-jiangshanlai@gmail.com Signed-off-by: Sasha Levin --- arch/x86/entry/entry_64.S | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index f1a8b5b2af964..f9e1c06a1c329 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -987,11 +987,6 @@ SYM_CODE_START_LOCAL(error_entry) pushq %r12 ret -.Lerror_entry_done_lfence: - FENCE_SWAPGS_KERNEL_ENTRY -.Lerror_entry_done: - ret - /* * There are two places in the kernel that can potentially fault with * usergs. Handle them here. B stepping K8s sometimes report a @@ -1014,8 +1009,14 @@ SYM_CODE_START_LOCAL(error_entry) * .Lgs_change's error handler with kernel gsbase. */ SWAPGS - FENCE_SWAPGS_USER_ENTRY - jmp .Lerror_entry_done + + /* + * Issue an LFENCE to prevent GS speculation, regardless of whether it is a + * kernel or user gsbase. + */ +.Lerror_entry_done_lfence: + FENCE_SWAPGS_KERNEL_ENTRY + ret .Lbstep_iret: /* Fix truncated RIP */ -- 2.33.0