From patchwork Mon Sep 20 14:28:56 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12505533 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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,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 5E8F6C433EF for ; Mon, 20 Sep 2021 14:30:47 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EB1AD60E76 for ; Mon, 20 Sep 2021 14:30:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org EB1AD60E76 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 8FE3F6B0074; Mon, 20 Sep 2021 10:30:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8ABA26B0075; Mon, 20 Sep 2021 10:30:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 79B58900002; Mon, 20 Sep 2021 10:30:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0118.hostedemail.com [216.40.44.118]) by kanga.kvack.org (Postfix) with ESMTP id 6CD4A6B0074 for ; Mon, 20 Sep 2021 10:30:46 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 2DE74181AEF3F for ; Mon, 20 Sep 2021 14:30:46 +0000 (UTC) X-FDA: 78608188092.07.FB2F255 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf20.hostedemail.com (Postfix) with ESMTP id C9AF2D000653 for ; Mon, 20 Sep 2021 14:30:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632148245; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=u9TCtQQQDHvFRzvXMYX+z7+x7whiCvDZBWtE0o8SjRw=; b=VqhcvlXI01zjumZd3g770X4X7tkiItq7nv9C74CMNeoUBwGuUNpHKJ8nHcIjcb/9xgAvOL hx4Ir8cbXtUYNHFH/aLCAyB+JIwKL3smfaZqy/RpF8dIruyEwIlk21mYT5HBCQCC93Yfcq W+I7OIcoSbjJRbJjIy79Uw7g9Z4SkUc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-379-lQdMcZHkM46HaswXCYi9-g-1; Mon, 20 Sep 2021 10:30:42 -0400 X-MC-Unique: lQdMcZHkM46HaswXCYi9-g-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 53797100C670; Mon, 20 Sep 2021 14:30:40 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.194.236]) by smtp.corp.redhat.com (Postfix) with ESMTP id 25EF660C17; Mon, 20 Sep 2021 14:30:35 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: David Hildenbrand , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. Tsirkin" , Jason Wang , "Rafael J. Wysocki" , Andrew Morton , Dan Williams , Hanjun Guo , Andy Shevchenko , virtualization@lists.linux-foundation.org, linux-mm@kvack.org Subject: [PATCH v5 3/3] virtio-mem: disallow mapping virtio-mem memory via /dev/mem Date: Mon, 20 Sep 2021 16:28:56 +0200 Message-Id: <20210920142856.17758-4-david@redhat.com> In-Reply-To: <20210920142856.17758-1-david@redhat.com> References: <20210920142856.17758-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C9AF2D000653 X-Stat-Signature: twr8tocmerkbp4nh3zswsybyzdyb7r8o Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=VqhcvlXI; spf=none (imf20.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-HE-Tag: 1632148245-306401 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Acked-by: Michael S. Tsirkin 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..0d974162899d 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 EXCLUSIVE_SYSTEM_RAM help This driver provides access to virtio-mem paravirtualized memory devices, allowing to hotplug and hotunplug memory. diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index bef8ad6bf466..c619bc0e46a7 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -2525,8 +2525,10 @@ 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");