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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 84FB6C3F2D2 for ; Tue, 3 Mar 2020 02:49:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A31B24684 for ; Tue, 3 Mar 2020 02:49:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583203774; bh=gEpI/WZAhYT91gRr4vJsYerumiMWnUy/i4/TlfwAmcY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=gtDeN9HHNZPfG/d4j1X8xbLO97jsCsI4iCgxZtsKpQ1r7nMl0w3HacrjpxCaLcelE 7V0YUUpS1MxXoks/KeFkO6KSXo6vtrVAlfUV90BFO4/xH3moVceoEbBHrk5rPFsWOZ BTkF7wIK9hUbQlLIMPQyG+m2xZAi5sAk4ehVQfBE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728900AbgCCCtc (ORCPT ); Mon, 2 Mar 2020 21:49:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:45730 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728895AbgCCCta (ORCPT ); Mon, 2 Mar 2020 21:49:30 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DC64E24684; Tue, 3 Mar 2020 02:49:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583203769; bh=gEpI/WZAhYT91gRr4vJsYerumiMWnUy/i4/TlfwAmcY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oDuVka1+F6KegRBwepafRVOZkgCK05HOBXr7yeXHhWk4tdHkmOH/KywqRb2x/kmUx n3zYItt9QCmpwOI79NO3fY6fLku4jYMwZFj1ELYCEb5r0sdbNeiV+O/18FBoAxujX0 hQQ3qCbZ68oQVoyf3LBIiPXmya/p1DYDm52PRKA0= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Kees Cook , Juergen Gross , Boris Ostrovsky , Sasha Levin , xen-devel@lists.xenproject.org, clang-built-linux@googlegroups.com Subject: [PATCH AUTOSEL 4.19 30/32] x86/xen: Distribute switch variables for initialization Date: Mon, 2 Mar 2020 21:48:49 -0500 Message-Id: <20200303024851.10054-30-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200303024851.10054-1-sashal@kernel.org> References: <20200303024851.10054-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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; -- 2.20.1