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 3BB1DC433EF for ; Fri, 26 Nov 2021 10:22:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376758AbhKZK0F (ORCPT ); Fri, 26 Nov 2021 05:26:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37452 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229505AbhKZKYE (ORCPT ); Fri, 26 Nov 2021 05:24:04 -0500 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2DBCEC061574 for ; Fri, 26 Nov 2021 02:12:08 -0800 (PST) Received: by mail-pl1-x62b.google.com with SMTP id p18so6352585plf.13 for ; Fri, 26 Nov 2021 02:12:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Zx01fK1SLqQ1j4TsG58btBXdwyGveKzyqnLszlU1jmU=; b=lSsyccXWquWd/0zdEf/qLmNniz/iQDKEgTgeL1N4+8xhLjvEKphBSRk9GeP81YEtZ1 wydZo5SwjMBX8KAdoLqbft8/VKs2zaJleQvkXli0rTGbwQoBDDpLgehUzwPEFI2B4A38 1VvLk4Senco+DuM4H22rsRzv2vkGNp6LNHt1K+5oZAerBhqBnjzbYzAY3H2wgrGKpBg+ 25iVD1f05hDp8vftilKDQO2Fu2zlIzR3x6ae39bd3+8VbNjY11433eIEc/rmNFI53wlP hNSDju5/A65AJaWHfgIfkYTxdkPYMrfhJ/FjaVvT3wOIgEpH+U6QHlalVZDkDqlsoxHZ 17OA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Zx01fK1SLqQ1j4TsG58btBXdwyGveKzyqnLszlU1jmU=; b=XWHJADCzhW/wp2/Up2hsIXdMSzncV6z0U0sFJpU7Z17yQIKjE5P88uFSpuoH+9uiFv QDsiKpB2W3CkFyFuda7zy5CTcOOv/KrcluKOFTwaZsXe2T7moHJXZi7bFWYAKlxVoDk3 cE+twVUIDid37BFNxJ6UoHtcqAyeK6yMkpAqw2C3KzVSB0OVPYnJsm+PmxEgCW1YLYuu 4vJJAYqFggst0/4+ezImPO1EGtMTyC8oj3gMGCUCQKYVYGrWwEBVexMIQFQCbUC+4zdp q+qerpdHqxVSnNsVN/P8yfdZ2dW44e9znUJb1bArpoKzZGN6wwDNLydyX0m3FpOpH7r8 /VQg== X-Gm-Message-State: AOAM532VJEsRlu2l9kaGUvHgCtCY5gH4HrD4tDDJ8YmAA/cIPPksRTIU G+BEcbIqpPa5q4qNz4BHKy7LWyRIEjg= X-Google-Smtp-Source: ABdhPJw6xdeeZ7uUjopKyLHSKzVakylonjAvPQ8ZkD5TTUa4VukkswjO5wsXN7f8MQTf2VOQJ4Ui6A== X-Received: by 2002:a17:90b:1b06:: with SMTP id nu6mr14385370pjb.155.1637921527584; Fri, 26 Nov 2021 02:12:07 -0800 (PST) Received: from localhost ([47.251.3.230]) by smtp.gmail.com with ESMTPSA id mv22sm5089395pjb.36.2021.11.26.02.12.06 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Nov 2021 02:12:07 -0800 (PST) From: Lai Jiangshan To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Lai Jiangshan , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Subject: [PATCH V6 02/49] x86/entry: Use the correct fence macro after swapgs in kernel CR3 Date: Fri, 26 Nov 2021 18:11:22 +0800 Message-Id: <20211126101209.8613-3-jiangshanlai@gmail.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20211126101209.8613-1-jiangshanlai@gmail.com> References: <20211126101209.8613-1-jiangshanlai@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan The commit c75890700455 ("x86/entry/64: Remove unneeded kernel CR3 switching") removes 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. Rahter, it depends on the CR3 write of SWITCH_TO_KERNEL_CR3. So the path should use FENCE_SWAPGS_KERNEL_ENTRY if SWITCH_TO_KERNEL_CR3 is removed. Fixes: c75890700455 ("x86/entry/64: Remove unneeded kernel CR3 switching") Signed-off-by: Lai Jiangshan --- arch/x86/entry/entry_64.S | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 8582709576bf..4967edded48d 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -991,11 +991,6 @@ 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 @@ -1018,8 +1013,15 @@ SYM_CODE_START_LOCAL(error_entry) * .Lgs_change's error handler with kernel gsbase. */ SWAPGS - FENCE_SWAPGS_USER_ENTRY - jmp .Lerror_entry_done + + /* + * The above code has no serializing instruction. So do an lfence + * to prevent GS speculation, regardless of whether it is kernel + * gsbase or user gsbase. + */ +.Lerror_entry_done_lfence: + FENCE_SWAPGS_KERNEL_ENTRY + ret .Lbstep_iret: /* Fix truncated RIP */ -- 2.19.1.6.gb485710b