From patchwork Wed Nov 11 14:53:16 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 323838 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=-9.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED 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 E1052C388F9 for ; Wed, 11 Nov 2020 14:54:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7C556206D9 for ; Wed, 11 Nov 2020 14:54:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="KpPZCt4J" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727257AbgKKOxm (ORCPT ); Wed, 11 Nov 2020 09:53:42 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:37160 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727245AbgKKOxm (ORCPT ); Wed, 11 Nov 2020 09:53:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605106421; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=HauqxgXColeqjprPbUc0JmWW3cRk97A/ix3dTNECW2k=; b=KpPZCt4JBTik3HGu/InAtfDKWKpzPUPcxhQpZRvc33BkEfv/tA0mWx29qWMxHkn1viA5kR lVewmc/E1QJ3PHLqgJNyPc2xn8XOqclwh2hfx/o8bBxLQcKCOgljvcdk1Yntwim68L3izi yT83UxlicaT04Q8OvD5T4aykPKPG71s= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-548-lQFt9juWPYGtGkNOXol1zQ-1; Wed, 11 Nov 2020 09:53:37 -0500 X-MC-Unique: lQFt9juWPYGtGkNOXol1zQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C6B0B879539; Wed, 11 Nov 2020 14:53:35 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-151.ams2.redhat.com [10.36.114.151]) by smtp.corp.redhat.com (Postfix) with ESMTP id D95D1380; Wed, 11 Nov 2020 14:53:33 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, David Hildenbrand , stable@vger.kernel.org, Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Rashmica Gupta Subject: [PATCH v2 2/8] powernv/memtrace: fix crashing the kernel when enabling concurrently Date: Wed, 11 Nov 2020 15:53:16 +0100 Message-Id: <20201111145322.15793-3-david@redhat.com> In-Reply-To: <20201111145322.15793-1-david@redhat.com> References: <20201111145322.15793-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org It's very easy to crash the kernel right now by simply trying to enable memtrace concurrently, hammering on the "enable" interface loop.sh: #!/bin/bash dmesg --console-off while true; do echo 0x40000000 > /sys/kernel/debug/powerpc/memtrace/enable done [root@localhost ~]# loop.sh & [root@localhost ~]# loop.sh & Resulting quickly in a kernel crash. Let's properly protect using a mutex. Fixes: 9d5171a8f248 ("powerpc/powernv: Enable removal of memory for in memory tracing") Cc: stable@vger.kernel.org# v4.14+ Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Rashmica Gupta Signed-off-by: David Hildenbrand Reviewed-by: Oscar Salvador --- arch/powerpc/platforms/powernv/memtrace.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c index eea1f94482ff..0e42fe2d7b6a 100644 --- a/arch/powerpc/platforms/powernv/memtrace.c +++ b/arch/powerpc/platforms/powernv/memtrace.c @@ -30,6 +30,7 @@ struct memtrace_entry { char name[16]; }; +static DEFINE_MUTEX(memtrace_mutex); static u64 memtrace_size; static struct memtrace_entry *memtrace_array; @@ -279,6 +280,7 @@ static int memtrace_online(void) static int memtrace_enable_set(void *data, u64 val) { + int rc = -EAGAIN; u64 bytes; /* @@ -291,25 +293,31 @@ static int memtrace_enable_set(void *data, u64 val) return -EINVAL; } + mutex_lock(&memtrace_mutex); + /* Re-add/online previously removed/offlined memory */ if (memtrace_size) { if (memtrace_online()) - return -EAGAIN; + goto out_unlock; } - if (!val) - return 0; + if (!val) { + rc = 0; + goto out_unlock; + } /* Offline and remove memory */ if (memtrace_init_regions_runtime(val)) - return -EINVAL; + goto out_unlock; if (memtrace_init_debugfs()) - return -EINVAL; + goto out_unlock; memtrace_size = val; - - return 0; + rc = 0; +out_unlock: + mutex_unlock(&memtrace_mutex); + return rc; } static int memtrace_enable_get(void *data, u64 *val)