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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 3CB74C4360C for ; Thu, 10 Oct 2019 07:38:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14C7E218AC for ; Thu, 10 Oct 2019 07:38:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570693111; bh=NL/tEtpoIxvVymAAXR8kmQMbwXwYwo1MzSsxWl1R5mY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=egkwHhzP78uNNdhJ+3BXmeoaARp0USzS1SgY7vUBJXqdVEbUftk2gxa8ptZ9PgFgP JrfV60+AlUb2UxgMLUn8TEBru9YZo7lzpE1/N1cQp3FO5P5EtG4VOIC2OeCVmLWgW8 LmbH6kDc2I5FUve8k7rpYL8lDiVneYWK5iKf3RS4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733306AbfJJHi3 (ORCPT ); Thu, 10 Oct 2019 03:38:29 -0400 Received: from mx2.suse.de ([195.135.220.15]:46604 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1733073AbfJJHd5 (ORCPT ); Thu, 10 Oct 2019 03:33:57 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id A5BF1B169; Thu, 10 Oct 2019 07:33:54 +0000 (UTC) Date: Thu, 10 Oct 2019 09:19:37 +0200 From: Michal Hocko To: Yizhuo Zhai Cc: Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zhiyun Qian , Chengyu Song Subject: Re: Potential NULL pointer deference in mm/memcontrol.c Message-ID: <20191010071937.GA18412@dhcp22.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 09-10-19 21:56:04, Yizhuo Zhai wrote: > Hi All: > mm/memcontrol.c: > The function mem_cgroup_from_css() could return NULL, but some callers This is the case only when the memory cgroup controller is disabled which is a boot time option. > in this file > checks the return value but directly dereference it, which seems > potentially unsafe. > Such callers include mem_cgroup_hierarchy_read(), > mem_cgroup_hierarchy_write(), mem_cgroup_read_u64(), > mem_cgroup_reset(), etc. And none of those should be ever called under that condition AFAICS. Thanks! -- Michal Hocko SUSE Labs