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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 52862C0044C for ; Thu, 1 Nov 2018 17:09:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F28BC20820 for ; Thu, 1 Nov 2018 17:09:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F28BC20820 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727546AbeKBCNl (ORCPT ); Thu, 1 Nov 2018 22:13:41 -0400 Received: from mx2.suse.de ([195.135.220.15]:36488 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725843AbeKBCNl (ORCPT ); Thu, 1 Nov 2018 22:13:41 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id CB3DBAE61; Thu, 1 Nov 2018 17:09:49 +0000 (UTC) Date: Thu, 1 Nov 2018 18:09:48 +0100 From: Michal Hocko To: miles.chen@mediatek.com Cc: Andrew Morton , Joe Perches , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com Subject: Re: [PATCH v4] mm/page_owner: clamp read count to PAGE_SIZE Message-ID: <20181101170948.GN23921@dhcp22.suse.cz> References: <1541091607-27402-1-git-send-email-miles.chen@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1541091607-27402-1-git-send-email-miles.chen@mediatek.com> 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 Fri 02-11-18 01:00:07, miles.chen@mediatek.com wrote: > From: Miles Chen > > The page owner read might allocate a large size of memory with > a large read count. Allocation fails can easily occur when doing > high order allocations. > > Clamp buffer size to PAGE_SIZE to avoid arbitrary size allocation > and avoid allocation fails due to high order allocation. It is good to mention that interface is root only so the harm due to unbounded allocation request is somehow reduced. I believe we want to use seq_file infrastructure in the long term solution. > Change since v3: > - remove the change in kvmalloc > - keep kmalloc in page_owner.c > > Change since v2: > - improve kvmalloc, allow sub page allocations fallback to > vmalloc when CONFIG_HIGHMEM=y > > Change since v1: > - use kvmalloc() > - clamp buffer size to PAGE_SIZE > > Signed-off-by: Miles Chen > Cc: Joe Perches > Cc: Matthew Wilcox > Cc: Michal Hocko Acked-by: Michal Hocko Thanks! > --- > mm/page_owner.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 87bc0dfdb52b..b83f295e4eca 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -351,6 +351,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn, > .skip = 0 > }; > > + count = count > PAGE_SIZE ? PAGE_SIZE : count; > kbuf = kmalloc(count, GFP_KERNEL); > if (!kbuf) > return -ENOMEM; > -- > 2.18.0 > -- Michal Hocko SUSE Labs