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=-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 A3BB1C10F27 for ; Tue, 10 Mar 2020 12:57:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A6D82468D for ; Tue, 10 Mar 2020 12:57:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583845067; bh=Ijmq/i5PFf8y/H7vXVaSKWPVJgkUToA6JgRLsQDTu7M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=JTb93PU0N++DE91Zgx1fgW+G8wR5jTMCHSQVcsrmP38BjoIVh95XUDTv2quayW3eI 9im3MfgEpAMDo2msSsyOPPW0z0RCOX5JzqnAMkC3ZdfqIsUv/kWpcJIBplEixiqxxf 4xe4mjWGLdkyunbWabkiozTWam1AJKRjnjTzfl6U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727384AbgCJM5q (ORCPT ); Tue, 10 Mar 2020 08:57:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:37538 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729801AbgCJM5n (ORCPT ); Tue, 10 Mar 2020 08:57:43 -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 24CBB20674; Tue, 10 Mar 2020 12:57:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583845062; bh=Ijmq/i5PFf8y/H7vXVaSKWPVJgkUToA6JgRLsQDTu7M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gHBDt/Is9XhIs5F+ywYIOLZ7yGeHmANu6GD02HqgpOVISkZUbNU/HY15YWc9TiiYb aMaMHxlk4gZqbc3QaUYDosNgqpKiXWQfJtUWajfwtJQ+uRh5gEd8hE0sVepxlvqnLt XzkHgIKrIWqgJotPv1ssXxkEO1n64+w4ongeQ6ec= 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 5.5 049/189] x86/xen: Distribute switch variables for initialization Date: Tue, 10 Mar 2020 13:38:06 +0100 Message-Id: <20200310123644.460773649@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200310123639.608886314@linuxfoundation.org> References: <20200310123639.608886314@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 1f756ffffe8b3..79409120a6036 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -896,14 +896,15 @@ 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; -- 2.20.1