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=-2.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_MED, USER_AGENT_NEOMUTT 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 7A33FECDFAA for ; Mon, 16 Jul 2018 14:47:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E4B4208AD for ; Mon, 16 Jul 2018 14:47:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="JPrF96ky" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E4B4208AD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shutemov.name 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 S1728290AbeGPPPb (ORCPT ); Mon, 16 Jul 2018 11:15:31 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:33795 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727328AbeGPPPb (ORCPT ); Mon, 16 Jul 2018 11:15:31 -0400 Received: by mail-pg1-f193.google.com with SMTP id y5-v6so7593702pgv.1 for ; Mon, 16 Jul 2018 07:47:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=/RrlAjlBz4vL/Kcd/+7/yrkfS4tpEbnBeA0cVabvIUI=; b=JPrF96kyx8xqknUqfl70ci7syj2UBphdKlZ1mwHj/M/GGdUWcR62N4ZHgN9i8z9Cal OqAlO1HZ6qXVV+Thw5cZQe1BvRtIrwV+G/8vMNtirbjsXVXKlXmBRm1Q1gdBDqDByBAO tI8a+vLUHAoplrFYhJl5JxPo+Ib8doRjoK53IInIiCK2fmxHOJudEz894QPiiDf9QeKJ aQnNUMRCcF4KBhwDevAyBTNY6u9EvCFP6g0WGWkEySl1AhuqGTiyWtD4R+FftPMhJmER lftaV22oQyBNWzTBCjTBfRA/f8oL3dlSbvqK05HSnhBHl0gFGMtf1ak4vJHs+XrlF3tL 0TUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=/RrlAjlBz4vL/Kcd/+7/yrkfS4tpEbnBeA0cVabvIUI=; b=Vrh9kbznukCdKlEgm+yd9KS/LWRI29Q3jGUfkxPT4QWlRFxFEuMOpWrNVPOd02KPRy 8T/Rmd7g+Guu5NGuXdadjObWRcy/la/MvH85rZ/W41Eczc+Fy4QYf5/le4AvtKG78xSb x9BbHPIQO74ulr/jEFg/MofyaUWUh8hA5pd82DNWjgUcdSZGSb4zXUw2xXZac+Cr/1+j SnIln184vO6tE7UrHbbBhxSLRNuCjY0d9Q4Pm9+St4FWsmNI797WSbpnK+NgPWGcTyqb WVbvQecmiZawFLiFFusB5865RiU6F3HzzBXrzzvN8ZpMKjkH5Z1u9PfPRfhJC0T049E2 q47Q== X-Gm-Message-State: AOUpUlHpisIl1TtKeLvKFf8MTraprGyByhdbYymGv/WtcJvWv7f5xDCf xZxuKRLWJxR3UXPDPosS67LWjg== X-Google-Smtp-Source: AAOMgpfloj1RL7NfCCre4aZAvlnp4P3t7u/1qz9M0KuQG8gicZmsOz9xlejtcMQZ531GHdr0kDfh2Q== X-Received: by 2002:a63:8f03:: with SMTP id n3-v6mr15917672pgd.166.1531752465520; Mon, 16 Jul 2018 07:47:45 -0700 (PDT) Received: from kshutemo-mobl1.localdomain ([134.134.139.83]) by smtp.gmail.com with ESMTPSA id q25-v6sm8115212pfk.96.2018.07.16.07.47.44 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Jul 2018 07:47:44 -0700 (PDT) Received: by kshutemo-mobl1.localdomain (Postfix, from userid 1000) id B35E83001F8; Mon, 16 Jul 2018 17:47:39 +0300 (+03) Date: Mon, 16 Jul 2018 17:47:39 +0300 From: "Kirill A. Shutemov" To: Michal Hocko Cc: "Kirill A. Shutemov" , Andrew Morton , Dmitry Vyukov , Oleg Nesterov , Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/2] mm: Fix vma_is_anonymous() false-positives Message-ID: <20180716144739.que5362bofty6ocp@kshutemo-mobl1> References: <20180710134821.84709-1-kirill.shutemov@linux.intel.com> <20180710134821.84709-2-kirill.shutemov@linux.intel.com> <20180710134858.3506f097104859b533c81bf3@linux-foundation.org> <20180716133028.GQ17280@dhcp22.suse.cz> <20180716140440.fd3sjw5xys5wozw7@black.fi.intel.com> <20180716142245.GT17280@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180716142245.GT17280@dhcp22.suse.cz> User-Agent: NeoMutt/20180622 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 16, 2018 at 04:22:45PM +0200, Michal Hocko wrote: > On Mon 16-07-18 17:04:41, Kirill A. Shutemov wrote: > > On Mon, Jul 16, 2018 at 01:30:28PM +0000, Michal Hocko wrote: > > > On Tue 10-07-18 13:48:58, Andrew Morton wrote: > > > > On Tue, 10 Jul 2018 16:48:20 +0300 "Kirill A. Shutemov" wrote: > > > > > > > > > vma_is_anonymous() relies on ->vm_ops being NULL to detect anonymous > > > > > VMA. This is unreliable as ->mmap may not set ->vm_ops. > > > > > > > > > > False-positive vma_is_anonymous() may lead to crashes: > > > > > > > > > > ... > > > > > > > > > > This can be fixed by assigning anonymous VMAs own vm_ops and not relying > > > > > on it being NULL. > > > > > > > > > > If ->mmap() failed to set ->vm_ops, mmap_region() will set it to > > > > > dummy_vm_ops. This way we will have non-NULL ->vm_ops for all VMAs. > > > > > > > > Is there a smaller, simpler fix which we can use for backporting > > > > purposes and save the larger rework for development kernels? > > > > > > Why cannot we simply keep anon vma with null vm_ops and set dummy_vm_ops > > > for all users who do not initialize it in their mmap callbacks? > > > Basically have a sanity check&fixup in call_mmap? > > > > As I said, there's a corner case of MAP_PRIVATE of /dev/zero. > > This is really creative. I really didn't think about that. I am > wondering whether this really has to be handled as a private anonymous > mapping implicitly. Why does vma_is_anonymous has to succeed for these > mappings? Why cannot we simply handle it as any other file backed > PRIVATE mapping? Because it's established way to create anonymous mappings in Linux. And we cannot break the semantics. -- Kirill A. Shutemov