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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 58263C10F03 for ; Sun, 10 Mar 2019 06:10:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2DE2E20657 for ; Sun, 10 Mar 2019 06:10:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725865AbfCJGKy convert rfc822-to-8bit (ORCPT ); Sun, 10 Mar 2019 01:10:54 -0500 Received: from terminus.zytor.com ([198.137.202.136]:55275 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725796AbfCJGKx (ORCPT ); Sun, 10 Mar 2019 01:10:53 -0500 Received: from [IPv6:2601:646:8680:2bb1:b911:67c8:ac46:1844] ([IPv6:2601:646:8680:2bb1:b911:67c8:ac46:1844]) (authenticated bits=0) by mail.zytor.com (8.15.2/8.15.2) with ESMTPSA id x2A6ATst3386469 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NO); Sat, 9 Mar 2019 22:10:30 -0800 Date: Sat, 09 Mar 2019 22:10:19 -0800 User-Agent: K-9 Mail for Android In-Reply-To: <20190308124904.216497374@linuxfoundation.org> References: <20190308124902.257040783@linuxfoundation.org> <20190308124904.216497374@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Subject: Re: [PATCH 5.0 30/46] x86/boot/compressed/64: Do not read legacy ROM on EFI system To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org CC: stable@vger.kernel.org, Pitam Mitra , "Kirill A. Shutemov" , Thomas Gleixner , Bockjoo Kim , bp@alien8.de From: hpa@zytor.com Message-ID: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On March 8, 2019 4:50:03 AM PST, Greg Kroah-Hartman wrote: >5.0-stable review patch. If anyone has any objections, please let me >know. > >------------------ > >From: Kirill A. Shutemov > >commit 6f913de3231e1d70a871135b38219da7810df218 upstream. > >EFI systems do not necessarily provide a legacy ROM. If the ROM is >missing >the memory is not mapped at all. > >Trying to dereference values in the legacy ROM area leads to a crash on >Macbook Pro. > >Only look for values in the legacy ROM area for non-EFI system. > >Fixes: 3548e131ec6a ("x86/boot/compressed/64: Find a place for 32-bit >trampoline") >Reported-by: Pitam Mitra >Signed-off-by: Kirill A. Shutemov >Signed-off-by: Thomas Gleixner >Tested-by: Bockjoo Kim >Cc: bp@alien8.de >Cc: hpa@zytor.com >Cc: stable@vger.kernel.org >Link: >https://lkml.kernel.org/r/20190219075224.35058-1-kirill.shutemov@linux.intel.com >Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=202351 >Signed-off-by: Greg Kroah-Hartman > >--- > arch/x86/boot/compressed/pgtable_64.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > >--- a/arch/x86/boot/compressed/pgtable_64.c >+++ b/arch/x86/boot/compressed/pgtable_64.c >@@ -1,5 +1,7 @@ >+#include > #include > #include >+#include > #include "pgtable.h" > #include "../string.h" > >@@ -37,9 +39,10 @@ int cmdline_find_option_bool(const char > > static unsigned long find_trampoline_placement(void) > { >- unsigned long bios_start, ebda_start; >+ unsigned long bios_start = 0, ebda_start = 0; > unsigned long trampoline_start; > struct boot_e820_entry *entry; >+ char *signature; > int i; > > /* >@@ -47,8 +50,18 @@ static unsigned long find_trampoline_pla > * This code is based on reserve_bios_regions(). > */ > >- ebda_start = *(unsigned short *)0x40e << 4; >- bios_start = *(unsigned short *)0x413 << 10; >+ /* >+ * EFI systems may not provide legacy ROM. The memory may not be >mapped >+ * at all. >+ * >+ * Only look for values in the legacy ROM for non-EFI system. >+ */ >+ signature = (char *)&boot_params->efi_info.efi_loader_signature; >+ if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) && >+ strncmp(signature, EFI64_LOADER_SIGNATURE, 4)) { >+ ebda_start = *(unsigned short *)0x40e << 4; >+ bios_start = *(unsigned short *)0x413 << 10; >+ } > > if (bios_start < BIOS_START_MIN || bios_start > BIOS_START_MAX) > bios_start = BIOS_START_MAX; Only one objection: the explanation is nonsensical. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.