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 EEE6DC433F5 for ; Thu, 24 Feb 2022 01:46:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229743AbiBXBqe (ORCPT ); Wed, 23 Feb 2022 20:46:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229739AbiBXBqd (ORCPT ); Wed, 23 Feb 2022 20:46:33 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18EAC141FC2; Wed, 23 Feb 2022 17:46:02 -0800 (PST) Received: from kwepemi500001.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4K3wDl2BGGzbbnh; Thu, 24 Feb 2022 09:24:39 +0800 (CST) Received: from kwepemm600009.china.huawei.com (7.193.23.164) by kwepemi500001.china.huawei.com (7.221.188.114) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Thu, 24 Feb 2022 09:29:10 +0800 Received: from [10.174.176.73] (10.174.176.73) by kwepemm600009.china.huawei.com (7.193.23.164) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Thu, 24 Feb 2022 09:29:10 +0800 Subject: Re: [PATCH RFC] blk-mq: fix potential uaf for 'queue_hw_ctx' To: Ming Lei CC: , , , References: <20220223112601.2902761-1-yukuai3@huawei.com> From: "yukuai (C)" Message-ID: Date: Thu, 24 Feb 2022 09:29:09 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.176.73] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemm600009.china.huawei.com (7.193.23.164) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org ÔÚ 2022/02/23 22:30, Ming Lei дµÀ: > On Wed, Feb 23, 2022 at 07:26:01PM +0800, Yu Kuai wrote: >> blk_mq_realloc_hw_ctxs() will free the 'queue_hw_ctx'(e.g. undate >> submit_queues through configfs for null_blk), while it might still be >> used from other context(e.g. switch elevator to none): >> >> t1 t2 >> elevator_switch >> blk_mq_unquiesce_queue >> blk_mq_run_hw_queues >> queue_for_each_hw_ctx >> // assembly code for hctx = (q)->queue_hw_ctx[i] >> mov 0x48(%rbp),%rdx -> read old queue_hw_ctx >> >> __blk_mq_update_nr_hw_queues >> blk_mq_realloc_hw_ctxs >> hctxs = q->queue_hw_ctx >> q->queue_hw_ctx = new_hctxs >> kfree(hctxs) >> movslq %ebx,%rax >> mov (%rdx,%rax,8),%rdi ->uaf >> > > Not only uaf on queue_hw_ctx, but also other similar issue on other > structures, and I think the correct and easy fix is to quiesce request > queue during updating nr_hw_queues, something like the following patch: > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index a05ce7725031..d8e7c3cce0dd 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -4467,8 +4467,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, > if (set->nr_maps == 1 && nr_hw_queues == set->nr_hw_queues) > return; > > - list_for_each_entry(q, &set->tag_list, tag_set_list) > + list_for_each_entry(q, &set->tag_list, tag_set_list) { > blk_mq_freeze_queue(q); > + blk_mq_quiesce_queue(q); > + } > /* > * Switch IO scheduler to 'none', cleaning up the data associated > * with the previous scheduler. We will switch back once we are done > @@ -4518,8 +4520,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, > list_for_each_entry(q, &set->tag_list, tag_set_list) > blk_mq_elv_switch_back(&head, q); > > - list_for_each_entry(q, &set->tag_list, tag_set_list) > + list_for_each_entry(q, &set->tag_list, tag_set_list) { > + blk_mq_unquiesce_queue(q); > blk_mq_unfreeze_queue(q); > + } > } > > void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues) Hi, Ming If blk_mq_quiesce_queue() is called from __blk_mq_update_nr_hw_queues() first, and then swithing elevator to none won't trigger the problem. However, what if blk_mq_unquiesce_queue() from switching elevator decrease quiesce_depth to 0 first, and then blk_mq_quiesce_queue() is called from __blk_mq_update_nr_hw_queues(), it seems to me such concurrent scenarios still exist. Thanks, Kuai > > > > Thanks, > Ming > > . >