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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2551FC433EF for ; Tue, 19 Apr 2022 03:55:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 91E8C8D0030; Mon, 18 Apr 2022 23:55:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8CE1C8D0026; Mon, 18 Apr 2022 23:55:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 797278D0030; Mon, 18 Apr 2022 23:55:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0219.hostedemail.com [216.40.44.219]) by kanga.kvack.org (Postfix) with ESMTP id 6AE318D0026 for ; Mon, 18 Apr 2022 23:55:36 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 0E8D51833821D for ; Tue, 19 Apr 2022 03:55:36 +0000 (UTC) X-FDA: 79372264272.30.DE2C995 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf25.hostedemail.com (Postfix) with ESMTP id 270C2A000A for ; Tue, 19 Apr 2022 03:55:34 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 03C67B81125; Tue, 19 Apr 2022 03:55:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E316C385A7; Tue, 19 Apr 2022 03:55:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1650340532; bh=nibgm+F/f0uCqZcCAC6pQ5BE8cFf97BjnCM7yu3WDcQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=x3HUvsmJ98Fg2AORmS7dNPTHsUkdoXLB+QBZ9l9ra7yTPsuluL8hOVQ9T4DK+WUs/ xC3pDpSNTqQ13lRQngWTJCYLdpl/LIxNa5hwWqx0R7Vw2BAnALet5Jj/46kU/WWhjv DluZUnMUXrrc1ulU79pNPDhgp/VY1QRzKORTaCuk= Date: Mon, 18 Apr 2022 20:55:31 -0700 From: Andrew Morton To: Miaohe Lin Cc: , , , , , David Hildenbrand Subject: Re: [PATCH 09/12] mm: compaction: avoid possible NULL pointer dereference in kcompactd_cpu_online Message-Id: <20220418205531.2e4ed0f72e0e537ef55c6468@linux-foundation.org> In-Reply-To: <20220418141253.24298-10-linmiaohe@huawei.com> References: <20220418141253.24298-1-linmiaohe@huawei.com> <20220418141253.24298-10-linmiaohe@huawei.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 270C2A000A X-Rspam-User: Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=x3HUvsmJ; spf=pass (imf25.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Stat-Signature: xoi6uk1y5enubc1cyetrergzjfj3etx7 X-HE-Tag: 1650340534-209247 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Please cc David H on memhotplug stuff. On Mon, 18 Apr 2022 22:12:50 +0800 Miaohe Lin wrote: > It's possible that kcompactd_run could fail to run kcompactd for a hot > added node and leave pgdat->kcompactd as NULL. So pgdat->kcompactd should > be checked here to avoid possible NULL pointer dereference. > > .. > > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -3052,7 +3052,8 @@ static int kcompactd_cpu_online(unsigned int cpu) > > if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) > /* One of our CPUs online: restore mask */ > - set_cpus_allowed_ptr(pgdat->kcompactd, mask); > + if (pgdat->kcompactd) > + set_cpus_allowed_ptr(pgdat->kcompactd, mask); > } > return 0; > } Why not fail to bring the node online if kcompactd_run() failed? Also, should we panic the system if kcompactd_run() failed in kcompactd_init()?