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 C358EC4332F for ; Thu, 17 Mar 2022 19:02:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237816AbiCQTDx (ORCPT ); Thu, 17 Mar 2022 15:03:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237814AbiCQTDw (ORCPT ); Thu, 17 Mar 2022 15:03:52 -0400 Received: from srv1.home.kabele.me (unknown [IPv6:2a02:768:2704:8c1a:3eec:efff:fe00:2ce4]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 879081F6856; Thu, 17 Mar 2022 12:02:35 -0700 (PDT) Received: from srv1.home.kabele.me (localhost [IPv6:::1]) by srv1.home.kabele.me (Postfix) with ESMTP id A5CB41692B1; Thu, 17 Mar 2022 20:02:38 +0100 (CET) Received: from localhost ([2a01:c22:8dfa:1400:beea:2810:7764:7afc]) by srv1.home.kabele.me with ESMTPSA id hQBTJc6FM2L9WDQAnmUwTQ (envelope-from ); Thu, 17 Mar 2022 20:02:38 +0100 Date: Thu, 17 Mar 2022 20:02:33 +0100 From: Vit Kabele To: platform-driver-x86@vger.kernel.org Cc: r.marek@assembler.cz, devel@acpica.org, mingo@redhat.com, robert.moore@intel.com, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org Subject: [PATCH 2/3 RESEND] acpica: Check that the EBDA pointer is in valid range Message-ID: Mail-Followup-To: platform-driver-x86@vger.kernel.org, r.marek@assembler.cz, devel@acpica.org, mingo@redhat.com, robert.moore@intel.com, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org If the memory at 0x40e is uninitialized, the retrieved physical_memory address of EBDA may be beyond the low memory (i.e. above 640K). If so, the kernel may unintentionally access the VGA memory, that might not be decoded or even present in case of virtualization. Signed-off-by: Vit Kabele Reviewed-by: Rudolf Marek --- drivers/acpi/acpica/tbxfroot.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/acpi/acpica/tbxfroot.c b/drivers/acpi/acpica/tbxfroot.c index 9fec3df6c3ba..67b7df1c0520 100644 --- a/drivers/acpi/acpica/tbxfroot.c +++ b/drivers/acpi/acpica/tbxfroot.c @@ -138,8 +138,11 @@ acpi_find_root_pointer(acpi_physical_address *table_address) acpi_os_unmap_memory(table_ptr, ACPI_EBDA_PTR_LENGTH); /* EBDA present? */ - - if (physical_address > 0x400) { + /* Check that the EBDA pointer from 0x40e is sane and does not point + * above valid low memory + */ + if (physical_address > 0x400 && + physical_address < 0xA0000) { /* * 1b) Search EBDA paragraphs (EBDA is required to be a * minimum of 1K length) -- 2.30.2