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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 67F04C43387 for ; Mon, 7 Jan 2019 05:28:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3365D20657 for ; Mon, 7 Jan 2019 05:28:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726273AbfAGF2U (ORCPT ); Mon, 7 Jan 2019 00:28:20 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:17118 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725300AbfAGF2T (ORCPT ); Mon, 7 Jan 2019 00:28:19 -0500 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 2ED2F9A25E917C6C7EE1; Mon, 7 Jan 2019 13:28:17 +0800 (CST) Received: from [127.0.0.1] (10.177.19.113) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.408.0; Mon, 7 Jan 2019 13:27:53 +0800 Subject: Re: [PATCH v2] nvme-pci: fix dbbuf_sq_db point to freed memory To: Christoph Hellwig References: <20190104180710.GA4642@infradead.org> CC: "axboe@kernel.dk" , "hch@lst.de" , "linux-kernel@vger.kernel.org" , "linux-nvme@lists.infradead.org" From: "Lulina (A)" Message-ID: <5C32E34D.3030705@huawei.com> Date: Mon, 7 Jan 2019 13:27:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <20190104180710.GA4642@infradead.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.177.19.113] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks for replying to my email, my description in the last email was not clear enough, so here's a supplementary note. The NVME device I used support DBBUF, but the nvme_admin_dbbuf request returned a failure that eventually led to the kernel crash. The problem occurs as follows: 1, Device support NVME_CTRL_OACS_DBBUF_SUPP，so reset worker alloc memory for dev->dbbuf_dbs。 2, In nvme_setup_io_queues process, the nvme_dbbuf_init function is called to assign values to pointers such as nvmeq->dbbuf_sq_db. 3, In nvme_dev_add function, the nvme_admin_dbbuf request is sent to the device, but the device returns failed, so the memory that dev->dbbuf_dbs points to is released. Then, the driver issued IO requests, in the nvme_write_sq_db process, nvme_dbbuf_update_and_check_event function judgment to Nvmeq->dbbuf_sq_db pointer is not NULL, write to the memory it points to, causing memory confusion and kernel crash. On 2019/1/5 2:07, Christoph Hellwig wrote: > On Fri, Dec 21, 2018 at 01:07:25AM +0000, Lulina (A) wrote: >> The case is that nvme device support NVME_CTRL_OACS_DBBUF_SUPP, and >> return failed when the driver sent nvme_admin_dbbuf. The nvmeq->dbbuf_sq_db >> point to freed memory, as nvme_dbbuf_set is called after nvme_dbbuf_init. > > But we never use those pointers in that state, do we? Can you explain > the problem in a little more detail? > >