From patchwork Tue Mar 10 12:44:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 229627 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 74B64C18E5B for ; Tue, 10 Mar 2020 13:14:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4DB1920409 for ; Tue, 10 Mar 2020 13:14:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583846059; bh=gEpI/WZAhYT91gRr4vJsYerumiMWnUy/i4/TlfwAmcY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=w2zhxYUW9VHklh/cEJ4Dj7yMe4QptL4XvT2uSCwmRLGFSFQ9ReX5X3dreQ03VWUc6 +gjOW2c+6WZOx5aOrzEX1eGRHylm8p7UUrfBfiyW9Qdg9Ov1v+GaKn50LrtLty4zF0 AWTdG+0gZRL/wJdHIAAVhSDV+upFcKUGMyTsDS1w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731462AbgCJNOS (ORCPT ); Tue, 10 Mar 2020 09:14:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:37904 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729264AbgCJNOS (ORCPT ); Tue, 10 Mar 2020 09:14:18 -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 3253224649; Tue, 10 Mar 2020 13:14:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583846057; bh=gEpI/WZAhYT91gRr4vJsYerumiMWnUy/i4/TlfwAmcY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P6xyhMiRpAzcMuQ7qGwMbG6WL0U+fZrCZYQPornA89q6lA6daO5s5yKM4/Zzo3ncS StOYsB0+mR3WyqbB+wMDcCpl9r1Lo00075Mzk/gdaf85lKuMXUxPgkkhs3jADqUhlf e+DbjfR5NnkxaxR/GHS5DUE6X73VqHVoyXNQa0cA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kees Cook , Juergen Gross , Boris Ostrovsky , Sasha Levin Subject: [PATCH 4.19 30/86] x86/xen: Distribute switch variables for initialization Date: Tue, 10 Mar 2020 13:44:54 +0100 Message-Id: <20200310124532.408826948@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200310124530.808338541@linuxfoundation.org> References: <20200310124530.808338541@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Kees Cook [ Upstream commit 9038ec99ceb94fb8d93ade5e236b2928f0792c7c ] Variables declared in a switch statement before any case statements cannot be automatically initialized with compiler instrumentation (as they are not part of any execution flow). With GCC's proposed automatic stack variable initialization feature, this triggers a warning (and they don't get initialized). Clang's automatic stack variable initialization (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also doesn't initialize such variables[1]. Note that these warnings (or silent skipping) happen before the dead-store elimination optimization phase, so even when the automatic initializations are later elided in favor of direct initializations, the warnings remain. To avoid these problems, move such variables into the "case" where they're used or lift them up into the main function body. arch/x86/xen/enlighten_pv.c: In function ‘xen_write_msr_safe’: arch/x86/xen/enlighten_pv.c:904:12: warning: statement will never be executed [-Wswitch-unreachable] 904 | unsigned which; | ^~~~~ [1] https://bugs.llvm.org/show_bug.cgi?id=44916 Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20200220062318.69299-1-keescook@chromium.org Reviewed-by: Juergen Gross [boris: made @which an 'unsigned int'] Signed-off-by: Boris Ostrovsky Signed-off-by: Sasha Levin --- arch/x86/xen/enlighten_pv.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 1730a26ff6abc..76864ea591605 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -908,14 +908,15 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err) static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high) { int ret; +#ifdef CONFIG_X86_64 + unsigned int which; + u64 base; +#endif ret = 0; switch (msr) { #ifdef CONFIG_X86_64 - unsigned which; - u64 base; - case MSR_FS_BASE: which = SEGBASE_FS; goto set; case MSR_KERNEL_GS_BASE: which = SEGBASE_GS_USER; goto set; case MSR_GS_BASE: which = SEGBASE_GS_KERNEL; goto set;