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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF475C433EF for ; Mon, 25 Apr 2022 23:57:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234204AbiDZAAk (ORCPT ); Mon, 25 Apr 2022 20:00:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231433AbiDZAAi (ORCPT ); Mon, 25 Apr 2022 20:00:38 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B2D63107700 for ; Mon, 25 Apr 2022 16:57:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=h5QXgxJ1aGDceWrYuG1jHB6di1JRZTFGfTsmuiIJuLI=; b=cTUxTt2w7Cd4Omul8GluhjKvMy IgxMLdp7R2egxMUOh8rwLY3KI0/ZvCAcQTwDCurSvPfX5otLeixPESApdXmQfs8+yozu3zD+UMeHD OJ1x09XCsoq4haPh6oh36mi25XLt7auXzvmyxLC4Mtj+eAaJyBGt7m5MDAmA3hjx38fo5ucw2c6HS hbewRNEZ9NrmSeu02balT5srjsLE1T49h9JCL9YSKWGkQzZkOEbRm2dgJlx+YvzesnTHYuepBOSuS rHe/KqZZRCRx+ie8Zn3Nwa6cZlO46wqX3/vs+8oBhBjksfxXhlTI4Q28TeOPkEc5U/gq5KcTvCx/s In5OO/CQ==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nj8a6-00BmLt-D2; Mon, 25 Apr 2022 23:57:26 +0000 Date: Mon, 25 Apr 2022 16:57:26 -0700 From: Luis Chamberlain To: Andrew Morton Cc: kernel test robot , Julius Hemanth Pitti , Johannes Weiner , Kees Cook , Iurii Zaikin , Ingo Molnar , Al Viro , LKML , lkp@lists.01.org, lkp@intel.com, Eli Cohen Subject: Re: [proc/sysctl] 1dd38979b2: BUG:kernel_NULL_pointer_dereference,address Message-ID: References: <20220425083302.GD21864@xsang-OptiPlex-9020> <20220425144607.2c2588e6b1f00ab8a6f3f6ea@linux-foundation.org> <20220425163434.5f8f47e8c301ea30c2f94a5a@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220425163434.5f8f47e8c301ea30c2f94a5a@linux-foundation.org> Sender: Luis Chamberlain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 25, 2022 at 04:34:34PM -0700, Andrew Morton wrote: > On Mon, 25 Apr 2022 16:08:57 -0700 Luis Chamberlain wrote: > > > On Mon, Apr 25, 2022 at 02:46:07PM -0700, Andrew Morton wrote: > > > On Mon, 25 Apr 2022 12:00:21 -0700 Luis Chamberlain wrote: > > > > > > > Andrew, can we drop this patch for now? > > > > > > I've been sitting on (ie, forgotten about) this patch > > > (https://lore.kernel.org/all/20200709235115.56954-1-jpitti@cisco.com/T/#u) > > > > Jesh, yeah I see. > > > > > for two years. Evidently waiting for you/Kees/Ingo to provide > > > guidance. So sure, the need seems very unurgent so I can drop it. > > > > Well Keew as OK with it, but I yeah I can't decipher the issue at this > > point in time. > > > > > However I fail to see how that patch could have caused this crash. I'm > > > suspecting a bisection error? > > > > > > Maybe something is unwell in drivers/vdpa/vdpa_user/vduse_dev.c. > > > > At a quick glance, yes it could very well by vduse_init() is messy and > > races somehow with init, but if a race does lurk here my instincts tell > > me this can't be the only place. > > > > Not sure if leaving a patch in place more time to see how else things > > can explode is worth it. > > Confused. Are you thinking that the above-linked patch was somehow > involved in this crash? If so, but how? All it does it to permit > unprivileged reads to four ints via proc_dointvec_minmax()? If the priv allows for it access to dereferencing a pointer is allowed. How that race happens though, indeed is beyond the patch's fault. Luis