From nobody Fri Apr 26 08:43:49 2024 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 EB869C433FE for ; Wed, 17 Nov 2021 02:11:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CBF3961BF5 for ; Wed, 17 Nov 2021 02:11:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232537AbhKQCOq (ORCPT ); Tue, 16 Nov 2021 21:14:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:50980 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229957AbhKQCOp (ORCPT ); Tue, 16 Nov 2021 21:14:45 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7572761507; Wed, 17 Nov 2021 02:11:47 +0000 (UTC) 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 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 =3D 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 =3D=3D 0) { + err =3D -ENOENT; + goto out_error; + } xen_store_gfn =3D (unsigned long)v; xen_store_interface =3D xen_remap(xen_store_gfn << XEN_PAGE_SHIFT, --=20 2.25.1