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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 CBBCBC433F5 for ; Fri, 3 Sep 2021 07:02:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B0BBE610A2 for ; Fri, 3 Sep 2021 07:02:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347532AbhICHDQ (ORCPT ); Fri, 3 Sep 2021 03:03:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:53910 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347087AbhICHDM (ORCPT ); Fri, 3 Sep 2021 03:03:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630652533; 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: in-reply-to:in-reply-to:references:references; bh=07FgH7wT67po2w8bQGIw93/1x6mvSaBB2yNe5PGszL8=; b=KfzTMChXoFsHlKFnQ3QLnB0Z15byHWp29rk0HWfCkQtgDev6rd355pPGfguT9/V4CHN2Kf /dJJKbXgvbB6gNA7glbJwbRRBLOsg3zc1l2dgw06z2/Hb9ExUs+r9RZP36J4kzooe+Uxjm jmckaga8qT+E/upbjRNLA8hzvnwYpt4= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-206-5IwTppg8MqCdmhQrBaTU7A-1; Fri, 03 Sep 2021 03:02:11 -0400 X-MC-Unique: 5IwTppg8MqCdmhQrBaTU7A-1 Received: by mail-wr1-f69.google.com with SMTP id 102-20020adf82ef000000b001576e345169so1258182wrc.7 for ; Fri, 03 Sep 2021 00:02:11 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=07FgH7wT67po2w8bQGIw93/1x6mvSaBB2yNe5PGszL8=; b=KfU+2yuhPjwkPpgs53BmlzUno1T2WIiw9SF2qz7hwWEZ5ji4I44BM/EuGsijlhyqjy 9o0kHbQK+OTF9HIgVSypGcgScGdO/3K2ndSxzoHFEEvMSqhkz8qlkQ6kSvv8XSE9RDA2 yqzjPJEtIfE1dMNCXWtJIbrchKHyZ/NKKZZvpmSreOe4lUJdfEXIfvb997JYvLG39zqe fQDOiWumwcdYx7Ug+f+3yO9HX7vLnWhU1sbPb+hrGWZpFAw63unhABk7dcElqAHTiYkV rjnW5JO4p7JpAnYmDwrlkBq4hlmNnQj79smp3oY0huimDnLap3wH7GOqzO+9G7/8Ru8q jbsw== X-Gm-Message-State: AOAM532UzRSb3CqJfJXpcxoFQPwWNosSVqG9HR9so1/Z3kftxpj7/rku UHUY5D8Fe3sBjLpKDRMMGDXovAYJzmWr8qkLvjS/0F81ki1LlyLeD4D08gyIXmt9v1RH+Y4Wy0X gO0gY0F5k441ux/OvOdZ/5VOS X-Received: by 2002:a5d:51c6:: with SMTP id n6mr2223510wrv.402.1630652530706; Fri, 03 Sep 2021 00:02:10 -0700 (PDT) X-Google-Smtp-Source: ABdhPJydsWfnmMs9uEFqCpYm22oyb0W/h3tDknscsNUxRfbHoKaj/53aSdqrSr8X//PvyYQLUFL9pw== X-Received: by 2002:a5d:51c6:: with SMTP id n6mr2223485wrv.402.1630652530498; Fri, 03 Sep 2021 00:02:10 -0700 (PDT) Received: from redhat.com ([2a03:c5c0:207f:7f47:ccd3:7600:6a2d:c5a]) by smtp.gmail.com with ESMTPSA id x9sm3336534wmi.30.2021.09.03.00.02.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Sep 2021 00:02:08 -0700 (PDT) Date: Fri, 3 Sep 2021 03:02:04 -0400 From: "Michael S. Tsirkin" To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Arnd Bergmann , Greg Kroah-Hartman , Jason Wang , "Rafael J. Wysocki" , Andrew Morton , Dan Williams , Hanjun Guo , Andy Shevchenko , virtualization@lists.linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH v4 3/3] virtio-mem: disallow mapping virtio-mem memory via /dev/mem Message-ID: <20210903025630-mutt-send-email-mst@kernel.org> References: <20210902160919.25683-1-david@redhat.com> <20210902160919.25683-4-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210902160919.25683-4-david@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 02, 2021 at 06:09:19PM +0200, David Hildenbrand wrote: > We don't want user space to be able to map virtio-mem device memory > directly (e.g., via /dev/mem) in order to have guarantees that in a sane > setup we'll never accidentially access unplugged memory within the > device-managed region of a virtio-mem device, just as required by the > virtio-spec. > > As soon as the virtio-mem driver is loaded, the device region is visible > in /proc/iomem via the parent device region. From that point on user space > is aware of the device region and we want to disallow mapping anything > inside that region (where we will dynamically (un)plug memory) until > the driver has been unloaded cleanly and e.g., another driver might take > over. > > By creating our parent IORESOURCE_SYSTEM_RAM resource with > IORESOURCE_EXCLUSIVE, we will disallow any /dev/mem access to our > device region until the driver was unloaded cleanly and removed the > parent region. This will work even though only some memory blocks are > actually currently added to Linux and appear as busy in the resource tree. > > So access to the region from user space is only possible > a) if we don't load the virtio-mem driver. > b) after unloading the virtio-mem driver cleanly. > > Don't build virtio-mem if access to /dev/mem cannot be restricticted -- > if we have CONFIG_DEVMEM=y but CONFIG_STRICT_DEVMEM is not set. > > Reviewed-by: Dan Williams > Signed-off-by: David Hildenbrand > --- > drivers/virtio/Kconfig | 1 + > drivers/virtio/virtio_mem.c | 4 +++- > 2 files changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig > index ce1b3f6ec325..ff80cd03f1d1 100644 > --- a/drivers/virtio/Kconfig > +++ b/drivers/virtio/Kconfig > @@ -101,6 +101,7 @@ config VIRTIO_MEM > depends on MEMORY_HOTPLUG_SPARSE > depends on MEMORY_HOTREMOVE > depends on CONTIG_ALLOC > + depends on !DEVMEM || STRICT_DEVMEM > help > This driver provides access to virtio-mem paravirtualized memory > devices, allowing to hotplug and hotunplug memory. It would be nicer if there was a symbol in the MEMORY_ namespace we can depend on exported by mm and depending on !DEVMEM || STRICT_DEVMEM. E.g. config MEMORY_EXCLUSIVE def_bool y depends on !DEVMEM || STRICT_DEVMEM and then in virtio depends on MEMORY_EXCLUSIVE the virtio change itself is ok though: Acked-by: Michael S. Tsirkin for merging through -mm. > diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c > index b91bc810a87e..c2d93492cf0f 100644 > --- a/drivers/virtio/virtio_mem.c > +++ b/drivers/virtio/virtio_mem.c > @@ -2523,8 +2523,10 @@ static int virtio_mem_create_resource(struct virtio_mem *vm) > if (!name) > return -ENOMEM; > > + /* Disallow mapping device memory via /dev/mem completely. */ > vm->parent_resource = __request_mem_region(vm->addr, vm->region_size, > - name, IORESOURCE_SYSTEM_RAM); > + name, IORESOURCE_SYSTEM_RAM | > + IORESOURCE_EXCLUSIVE); > if (!vm->parent_resource) { > kfree(name); > dev_warn(&vm->vdev->dev, "could not reserve device region\n"); > -- > 2.31.1