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 D293AC433FE for ; Mon, 6 Dec 2021 14:58:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344791AbhLFPCS (ORCPT ); Mon, 6 Dec 2021 10:02:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344691AbhLFPCM (ORCPT ); Mon, 6 Dec 2021 10:02:12 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77634C0613F8; Mon, 6 Dec 2021 06:58:43 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 38C57B81018; Mon, 6 Dec 2021 14:58:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 813E5C341C5; Mon, 6 Dec 2021 14:58:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1638802720; bh=rDQtwXULIRUdDIKjJJLmJvvfGOAlGmQYSWA+poLGulA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uFD7MSV8C72d8m3a+mxB+iubQ9vyqBpjCi68hKNLgcJ0CsAAo505Z9w5zEi2n6E+H /xttAGqa+Pn+lZ9PTBv4sCTTn6PHUZD9V5MxheEkyyqmMABd0RiinN8oHrGuV2pWqC PvXf3e59hNnygyA51rN0pA1JjtjzCEGgNqeibYAM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stefano Stabellini , Juergen Gross , Jan Beulich , Boris Ostrovsky Subject: [PATCH 4.4 10/52] xen: detect uninitialized xenbus in xenbus_init Date: Mon, 6 Dec 2021 15:55:54 +0100 Message-Id: <20211206145548.242923818@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211206145547.892668902@linuxfoundation.org> References: <20211206145547.892668902@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Stefano Stabellini commit 36e8f60f0867d3b70d398d653c17108459a04efe upstream. 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. Also recognize all bits set as an invalid value. For 32-bit Linux, any pfn above ULONG_MAX would get truncated. Pfns above ULONG_MAX should never be passed by the Xen tools to HVM guests anyway, so check for this condition and return early. Cc: stable@vger.kernel.org Signed-off-by: Stefano Stabellini Reviewed-by: Juergen Gross Reviewed-by: Jan Beulich Link: https://lore.kernel.org/r/20211123210748.1910236-1-sstabellini@kernel.org Signed-off-by: Boris Ostrovsky Signed-off-by: Greg Kroah-Hartman --- drivers/xen/xenbus/xenbus_probe.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) --- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -804,6 +804,29 @@ 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. + * + * Also recognize all bits set as an invalid value. + */ + if (!v || !~v) { + err = -ENOENT; + goto out_error; + } + /* Avoid truncation on 32-bit. */ +#if BITS_PER_LONG == 32 + if (v > ULONG_MAX) { + pr_err("%s: cannot handle HVM_PARAM_STORE_PFN=%llx > ULONG_MAX\n", + __func__, v); + err = -EINVAL; + goto out_error; + } +#endif xen_store_gfn = (unsigned long)v; xen_store_interface = xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,