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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 C3D42C433E0 for ; Mon, 18 Jan 2021 19:20:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B6F422573 for ; Mon, 18 Jan 2021 19:20:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437219AbhARTUA (ORCPT ); Mon, 18 Jan 2021 14:20:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:34128 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390488AbhARLip (ORCPT ); Mon, 18 Jan 2021 06:38:45 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id B194F22BEA; Mon, 18 Jan 2021 11:38:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610969887; bh=4SfJdloB45KTxytxtJ2ZFq4iDMuLZiL5ji8CUdcueb4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=d4vINXWNaEvSugNUaUvuffLJoUdNfYf39GrA/luljFAnEnuA6kDUg/UiSMQiFAq3o qCYsGkRH7b2KEHwnWV0kurgcJRPVge0fZ43YI2IBCEoVYsNOUV4G0saarod3FpR4vU Yj11IbiEHb6w6hUD7bN3fxBOoaFzBCIzatDWM0ro= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Wei Liu , stable@kernel.org, Michael Kelley Subject: [PATCH 5.4 04/76] x86/hyperv: check cpu mask after interrupt has been disabled Date: Mon, 18 Jan 2021 12:34:04 +0100 Message-Id: <20210118113341.197374462@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210118113340.984217512@linuxfoundation.org> References: <20210118113340.984217512@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: Wei Liu commit ad0a6bad44758afa3b440c254a24999a0c7e35d5 upstream. We've observed crashes due to an empty cpu mask in hyperv_flush_tlb_others. Obviously the cpu mask in question is changed between the cpumask_empty call at the beginning of the function and when it is actually used later. One theory is that an interrupt comes in between and a code path ends up changing the mask. Move the check after interrupt has been disabled to see if it fixes the issue. Signed-off-by: Wei Liu Cc: stable@kernel.org Link: https://lore.kernel.org/r/20210105175043.28325-1-wei.liu@kernel.org Reviewed-by: Michael Kelley Signed-off-by: Greg Kroah-Hartman --- arch/x86/hyperv/mmu.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/arch/x86/hyperv/mmu.c +++ b/arch/x86/hyperv/mmu.c @@ -66,11 +66,17 @@ static void hyperv_flush_tlb_others(cons if (!hv_hypercall_pg) goto do_native; - if (cpumask_empty(cpus)) - return; - local_irq_save(flags); + /* + * Only check the mask _after_ interrupt has been disabled to avoid the + * mask changing under our feet. + */ + if (cpumask_empty(cpus)) { + local_irq_restore(flags); + return; + } + flush_pcpu = (struct hv_tlb_flush **) this_cpu_ptr(hyperv_pcpu_input_arg);