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=-12.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 48B6EC433E0 for ; Thu, 21 Jan 2021 21:34:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0ADD723A53 for ; Thu, 21 Jan 2021 21:34:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727356AbhAUVdI (ORCPT ); Thu, 21 Jan 2021 16:33:08 -0500 Received: from mail.kernel.org ([198.145.29.99]:38276 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727305AbhAUVb6 (ORCPT ); Thu, 21 Jan 2021 16:31:58 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9E23E23A53; Thu, 21 Jan 2021 21:31:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611264675; bh=L5lsmNVyN/gM7eKC23++Z8NFz5Zp1K8u7Gf3EzsLgTA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=s3E9tnK1u5bQtDZDhFxLwTEjQoye8OEe0JSXIIJXh59aGqORZ3Q8zdNRiWOaMY+g0 TyUNgL3pMTFaj2i3ooCy4cYUQgvFaWz8j3pr7ekeyTHWMRQm9QUVerC+yaSarK3yAv k+nnKZRsH9DipeZjI+Gyv2WfmmJpfAvnKNk38ZgnZtopWjVX/ds6YZFCJlf7Fzsgmw rtNd74QkiodsM0W+U02QglBYZ24GfAaF4uX1/H7V2igVdCZbkDbyUU9SgJ8QuK+MpZ bvOiVG6YGB0g+tiI+r4SIy132vvXRgO3YyF2zsSGpEidBTJBECm2W4/wcn4D2sWSrO m+qCinZgzKkHw== Date: Thu, 21 Jan 2021 21:31:10 +0000 From: Will Deacon To: "Paul E. McKenney" Cc: Naresh Kamboju , rcu@vger.kernel.org, open list , Linux-Next Mailing List , lkft-triage@lists.linaro.org, Peter Zijlstra , Steven Rostedt , Ingo Molnar , catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, vincenzo.frascino@arm.com, mark.rutland@arm.com Subject: Re: rcu-torture: Internal error: Oops: 96000006 Message-ID: <20210121213110.GB23234@willie-the-truck> References: <20210121185521.GQ2743@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210121185521.GQ2743@paulmck-ThinkPad-P72> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Thu, Jan 21, 2021 at 10:55:21AM -0800, Paul E. McKenney wrote: > On Thu, Jan 21, 2021 at 10:37:21PM +0530, Naresh Kamboju wrote: > > While running rcu-torture test on qemu_arm64 and arm64 Juno-r2 device > > the following kernel crash noticed. This started happening from Linux next > > next-20210111 tag to next-20210121. > > > > metadata: > > git branch: master > > git repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next > > git describe: next-20210111 > > kernel-config: https://builds.tuxbuild.com/1muTTn7AfqcWvH5x2Alxifn7EUH/config > > > > output log: > > > > [ 621.538050] mem_dump_obj() slab test: rcu_torture_stats = > > ffff0000c0a3ac40, &rhp = ffff800012debe40, rhp = ffff0000c8cba000, &z > > = ffff8000091ab8e0 > > [ 621.546662] mem_dump_obj(ZERO_SIZE_PTR): > > [ 621.546696] Unable to handle kernel NULL pointer dereference at > > virtual address 0000000000000008 [...] > Huh. I am relying on virt_addr_valid() rejecting NULL pointers and > things like ZERO_SIZE_PTR, which is defined as ((void *)16). It looks > like your configuration rejects NULL as an invalid virtual address, > but does not reject ZERO_SIZE_PTR. Is this the intent, given that you > are not allowed to dereference a ZERO_SIZE_PTR? > > Adding the ARM64 guys on CC for their thoughts. Spooky timing, there was a thread _today_ about that: https://lore.kernel.org/r/ecbc7651-82c4-6518-d4a9-dbdbdf833b5b@arm.com Will