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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D4275C2BB1D for ; Wed, 15 Apr 2020 02:02:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7930206D9 for ; Wed, 15 Apr 2020 02:02:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392840AbgDOCCD (ORCPT ); Tue, 14 Apr 2020 22:02:03 -0400 Received: from mga05.intel.com ([192.55.52.43]:40304 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392789AbgDOCB5 (ORCPT ); Tue, 14 Apr 2020 22:01:57 -0400 IronPort-SDR: TxEr8Kj0dMWMhLLIKlDjaSS4qPK087B27BYnFZWOjdjpvpI9IKiTGeZcY5r9wv5AhGFbs9VBri nGLDtsaQNoVA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Apr 2020 19:01:56 -0700 IronPort-SDR: Hmt0b3bWk3FGU0LKmcKgQ0wNl3GKIVKo4Fb+10Tv+bsqQf9j0sO0wYR8CZxlB27WI+ElswuQJu QGh6XA0w7J5Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,385,1580803200"; d="scan'208";a="242172668" Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.23]) by orsmga007.jf.intel.com with ESMTP; 14 Apr 2020 19:01:54 -0700 From: "Huang\, Ying" To: Qian Cai Cc: Linux-MM , LKML , Minchan Kim , Hugh Dickins , "Andrew Morton" Subject: Re: linux-next: not-present page at swap_vma_readahead() References: <62A0ACFC-E023-4269-8121-F96B879A8C51@lca.pw> <81F06AA9-F25B-4342-9CF7-2763AC394A18@lca.pw> Date: Wed, 15 Apr 2020 10:01:53 +0800 In-Reply-To: <81F06AA9-F25B-4342-9CF7-2763AC394A18@lca.pw> (Qian Cai's message of "Tue, 14 Apr 2020 17:22:54 -0400") Message-ID: <874ktl1p7y.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Qian Cai writes: >> On Apr 14, 2020, at 10:32 AM, Qian Cai wrote: >> >> Fuzzers are unhappy. Thoughts? > > This is rather to reproduce. All the traces so far are from copy_from_user() to trigger a page fault, > and then it dereferences a bad pte in swap_vma_readahead(), > > for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte; > i++, pte++) { > pentry = *pte; <— crashed here. > if (pte_none(pentry)) Is it possible to bisect this? Because the crash point is identified, it may be helpful to collect and analyze the status of the faulting page table and readahead ptes. But I am not familiar with the ARM64 architecture. So I cannot help much here. Best Regards, Huang, Ying