From patchwork Wed Nov 17 02:11:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefano Stabellini X-Patchwork-Id: 12623541 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CEA25C433F5 for ; Wed, 17 Nov 2021 02:12:26 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 830F063222 for ; Wed, 17 Nov 2021 02:12:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 830F063222 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.226591.391595 (Exim 4.92) (envelope-from ) id 1mnAQT-0003LE-KD; Wed, 17 Nov 2021 02:11:53 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 226591.391595; Wed, 17 Nov 2021 02:11:53 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mnAQT-0003L7-GZ; Wed, 17 Nov 2021 02:11:53 +0000 Received: by outflank-mailman (input) for mailman id 226591; Wed, 17 Nov 2021 02:11:52 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mnAQS-0003Kv-5y for xen-devel@lists.xenproject.org; Wed, 17 Nov 2021 02:11:52 +0000 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id b7ec6bbb-474b-11ec-a9d2-d9f7a1cc8784; Wed, 17 Nov 2021 03:11:48 +0100 (CET) Received: by mail.kernel.org (Postfix) with ESMTPSA id 7572761507; Wed, 17 Nov 2021 02:11:47 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: b7ec6bbb-474b-11ec-a9d2-d9f7a1cc8784 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1637115107; bh=1sJR+x8QSuLwW/kR5p/1Dip3rvuByc6vAKciM3MxL+Q=; h=From:To:Cc:Subject:Date:From; b=g/XwgabaeLNS1AEjamMRtCcZFcGKZDMcoxKQ3cvC3A22/ImQv7CGvtc0Mbwi6m2sg bGnHNmvAII0X2EyopbfdL9zDsV+ThTWDe94DVWl8N0tapFDZRHdicZj9fz0vsrjj8N VmfvxLWhqkUJ46iL7GYKyKz/i6UnlQg7h+YukiqajqMKhFZvG88mdJLlgx67u2WPzc 7HqbDdrzIz6eIctAYlpHZjnbK/qqQZw58tD4eqc7gsCqJoi+Plj2W72D07W6LRtTkz tHmnE7xJk4ZlwPG3Q7f2jvMt5q56osyqq9IUXemY6OKzM1r8Ad9L2KB3aMKPKdPBqR lUJmhzwT0tR0g== From: Stefano Stabellini To: jgross@suse.com Cc: boris.ostrovsky@oracle.com, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, sstabellini@kernel.org, jbeulich@suse.com, Stefano Stabellini , stable@vger.kernel.org Subject: [PATCH] xen: detect uninitialized xenbus in xenbus_init Date: Tue, 16 Nov 2021 18:11:45 -0800 Message-Id: <20211117021145.3105042-1-sstabellini@kernel.org> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 From: Stefano Stabellini If the xenstore page hasn't been allocated properly, reading the value of the related hvm_param (HVM_PARAM_STORE_PFN) won't actually return error. Instead, it will succeed and return zero. Instead of attempting to xen_remap a bad guest physical address, detect this condition and return early. Note that although a guest physical address of zero for HVM_PARAM_STORE_PFN is theoretically possible, it is not a good choice and zero has never been validly used in that capacity. Cc: stable@vger.kernel.org Signed-off-by: Stefano Stabellini --- drivers/xen/xenbus/xenbus_probe.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c index 94405bb3829e..c89de0062399 100644 --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -951,6 +951,18 @@ static int __init xenbus_init(void) err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v); if (err) goto out_error; + /* + * Uninitialized hvm_params are zero and return no error. + * Although it is theoretically possible to have + * HVM_PARAM_STORE_PFN set to zero on purpose, in reality it is + * not zero when valid. If zero, it means that Xenstore hasn't + * been properly initialized. Instead of attempting to map a + * wrong guest physical address return error. + */ + if (v == 0) { + err = -ENOENT; + goto out_error; + } xen_store_gfn = (unsigned long)v; xen_store_interface = xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,