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 01E55CE7B09 for ; Thu, 28 Sep 2023 07:41:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230439AbjI1Hlv (ORCPT ); Thu, 28 Sep 2023 03:41:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43796 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230394AbjI1Hlt (ORCPT ); Thu, 28 Sep 2023 03:41:49 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 351568F for ; Thu, 28 Sep 2023 00:41:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695886865; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ik4NJ/TGlJZz+KHb//NIC0FfeN79I9S7Nn+XpOdL4hI=; b=LQqRx9n2vKqp3TjsbaloRgDvIRjDa/UfgzzGG00UHLHllWtgCglMXivOWaHxTAd3ru9Aj2 Yli0862mhXdEXksaqlaS6ZY82vTCpitURAR/u2dfMGLCorNCtrgFIkoGiXIRtjbZNyqI/d VUkzMsO3Z8oqko95vo1XX3lKU6ncOOI= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-251-PUt-YSMNMSWUFoSPp6bpuQ-1; Thu, 28 Sep 2023 03:41:00 -0400 X-MC-Unique: PUt-YSMNMSWUFoSPp6bpuQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 337CF185A79B; Thu, 28 Sep 2023 07:41:00 +0000 (UTC) Received: from fedora (unknown [10.72.120.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 62923C15BB8; Thu, 28 Sep 2023 07:40:51 +0000 (UTC) Date: Thu, 28 Sep 2023 15:40:46 +0800 From: Ming Lei To: Yu Kuai Cc: linan666@huaweicloud.com, josef@toxicpanda.com, axboe@kernel.dk, linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org, linan122@huawei.com, yi.zhang@huawei.com, houtao1@huawei.com, yangerkun@huawei.com, "yukuai (C)" , ming.lei@redhat.com Subject: Re: [PATCH] nbd: pass nbd_sock to nbd_read_reply() instead of index Message-ID: References: <20230911023308.3467802-1-linan666@huaweicloud.com> <47669fb6-3700-e327-11af-93a92b0984a0@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <47669fb6-3700-e327-11af-93a92b0984a0@huaweicloud.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 28, 2023 at 02:03:28PM +0800, Yu Kuai wrote: > Hi, > > 在 2023/09/28 12:05, Ming Lei 写道: > > On Mon, Sep 11, 2023 at 10:33:08AM +0800, linan666@huaweicloud.com wrote: > > > From: Li Nan > > > > > > If a socket is processing ioctl 'NBD_SET_SOCK', config->socks might be > > > krealloc in nbd_add_socket(), and a garbage request is received now, a UAF > > > may occurs. > > > > > > T1 > > > nbd_ioctl > > > __nbd_ioctl > > > nbd_add_socket > > > blk_mq_freeze_queue > > > T2 > > > recv_work > > > nbd_read_reply > > > sock_xmit > > > krealloc config->socks > > > def config->socks > > > > > > Pass nbd_sock to nbd_read_reply(). And introduce a new function > > > sock_xmit_recv(), which differs from sock_xmit only in the way it get > > > socket. > > > > > > > I am wondering why not grab queue usage counter before calling nbd_read_reply() > > for avoiding such issue, something like the following change: > > > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > > index df1cd0f718b8..09215b605b12 100644 > > --- a/drivers/block/nbd.c > > +++ b/drivers/block/nbd.c > > @@ -837,9 +837,6 @@ static void recv_work(struct work_struct *work) > > while (1) { > > struct nbd_reply reply; > > - if (nbd_read_reply(nbd, args->index, &reply)) > > - break; > > - > > /* > > * Grab .q_usage_counter so request pool won't go away, then no > > * request use-after-free is possible during nbd_handle_reply(). > > @@ -852,6 +849,9 @@ static void recv_work(struct work_struct *work) > > break; > > } > > This break how nbd works, if there is no reply yet, recv_work() will > wait for reply in: > > nbd_read_reply > sock_xmit > sock_recvmsg > > After this change, recv_work() will just return if there is no io. OK, got it, thanks for the input. But I feel it isn't necessary & fragile to store one extra reference of nsock in `recv_thread_args`. Just run a quick look, the only potential UAF on config->socks should be recv_work(), so you can retrieve the `nsock` reference at the entry of recv_work(), and just pass it(local variable) to nbd_read_reply() and nbd_handle_reply() since `nsock` won't be freed. Thanks, Ming