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=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 2A074C433E0 for ; Fri, 19 Jun 2020 16:51:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05281206B7 for ; Fri, 19 Jun 2020 16:51:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592585484; bh=Uw9/vRLVgKmqGjw40c38O9e7lpuxn5NHt5DzieU+7Dk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=XCE6rb3kKqEJmTOxVjvh9662hbR7yh92GEr4FkbVdE7lV5gHqP2xAAxKcSCiFSkJk HBm27tZIngAhCY/NbdxLsYW72soRJt77WRhoszmWAqNO6MhO1F/KVQIZiG3Dd6hu8z Jjc8lYLNkHdlQoA9IRQVFdQSEbJOosryu66ZY5TQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405875AbgFSQvO (ORCPT ); Fri, 19 Jun 2020 12:51:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:55190 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733301AbgFSOiL (ORCPT ); Fri, 19 Jun 2020 10:38:11 -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 98B2B208B8; Fri, 19 Jun 2020 14:38:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592577491; bh=Uw9/vRLVgKmqGjw40c38O9e7lpuxn5NHt5DzieU+7Dk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DniKQu16FzvSdTDCfI1IC2lhO6X/ofjhKUDWuTXyhDoSL2op8D/dyAvNItU8FjMbA 3qfxNrXu7dAkOx/PJxnMDERIoyzRnVIxXM0lvyiKuwGuQdU9YAwx7CviIlzOTfmAVH NAXdXfXTu+uhT89uUbNd0MwqUF4xM9ihzRNr7DVs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Will Deacon , Douglas Anderson , Daniel Thompson , Sasha Levin Subject: [PATCH 4.4 064/101] kgdb: Fix spurious true from in_dbg_master() Date: Fri, 19 Jun 2020 16:32:53 +0200 Message-Id: <20200619141617.408531048@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200619141614.001544111@linuxfoundation.org> References: <20200619141614.001544111@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: Daniel Thompson [ Upstream commit 3fec4aecb311995189217e64d725cfe84a568de3 ] Currently there is a small window where a badly timed migration could cause in_dbg_master() to spuriously return true. Specifically if we migrate to a new core after reading the processor id and the previous core takes a breakpoint then we will evaluate true if we read kgdb_active before we get the IPI to bring us to halt. Fix this by checking irqs_disabled() first. Interrupts are always disabled when we are executing the kgdb trap so this is an acceptable prerequisite. This also allows us to replace raw_smp_processor_id() with smp_processor_id() since the short circuit logic will prevent warnings from PREEMPT_DEBUG. Fixes: dcc7871128e9 ("kgdb: core changes to support kdb") Suggested-by: Will Deacon Link: https://lore.kernel.org/r/20200506164223.2875760-1-daniel.thompson@linaro.org Reviewed-by: Douglas Anderson Signed-off-by: Daniel Thompson Signed-off-by: Sasha Levin --- include/linux/kgdb.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h index e465bb15912d..6be5545d3584 100644 --- a/include/linux/kgdb.h +++ b/include/linux/kgdb.h @@ -317,7 +317,7 @@ extern void gdbstub_exit(int status); extern int kgdb_single_step; extern atomic_t kgdb_active; #define in_dbg_master() \ - (raw_smp_processor_id() == atomic_read(&kgdb_active)) + (irqs_disabled() && (smp_processor_id() == atomic_read(&kgdb_active))) extern bool dbg_is_early; extern void __init dbg_late_init(void); #else /* ! CONFIG_KGDB */ -- 2.25.1