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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 4D068C32751 for ; Sun, 11 Aug 2019 02:30:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 15D1420880 for ; Sun, 11 Aug 2019 02:30:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726530AbfHKCaR (ORCPT ); Sat, 10 Aug 2019 22:30:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34834 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726292AbfHKCaR (ORCPT ); Sat, 10 Aug 2019 22:30:17 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8EFBF3DE0F; Sun, 11 Aug 2019 02:30:16 +0000 (UTC) Received: from localhost.localdomain (ovpn-12-36.pek2.redhat.com [10.72.12.36]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B5326100195F; Sun, 11 Aug 2019 02:30:00 +0000 (UTC) Subject: Re: crash: `kmem -s` reported "kmem: dma-kmalloc-512: slab: ffffe192c0001000 invalid freepointer: e5ffef4e9a040b7e" on a dumped vmcore To: "Lendacky, Thomas" , Dave Young Cc: "linux-kernel@vger.kernel.org" , Dave Anderson , "kexec@lists.infradead.org" , "vgoyal@redhat.com" , "bhe@redhat.com" , "ebiederm@xmission.com" References: <20190802010538.GA2202@dhcp-128-65.nay.redhat.com> <5d91e856-01de-bc80-e4bc-497d57652072@amd.com> From: lijiang Message-ID: <2d3c7ab8-0b83-4ef5-bb89-0c7c476265b3@redhat.com> Date: Sun, 11 Aug 2019 10:29:57 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <5d91e856-01de-bc80-e4bc-497d57652072@amd.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Sun, 11 Aug 2019 02:30:16 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2019年08月09日 06:37, Lendacky, Thomas 写道: > On 8/1/19 8:05 PM, Dave Young wrote: >> Add kexec cc list. >> On 08/01/19 at 11:02pm, lijiang wrote: >>> Hi, Tom >>> >>> Recently, i ran into a problem about SME and used crash tool to check the vmcore as follow: >>> >>> crash> kmem -s | grep -i invalid >>> kmem: dma-kmalloc-512: slab: ffffe192c0001000 invalid freepointer: e5ffef4e9a040b7e >>> kmem: dma-kmalloc-512: slab: ffffe192c0001000 invalid freepointer: e5ffef4e9a040b7e >>> >>> And the crash tool reported the above error, probably, the main reason is that kernel does not >>> correctly handle the first 640k region when SME is enabled. >>> >>> When SME is enabled, the kernel and initramfs images are loaded into the decrypted memory, and >>> the backup area(first 640k) is also mapped as decrypted, but the first 640k data is copied to >>> the backup area in purgatory(). Please refer to this file: arch/x86/purgatory/purgatory.c >>> ...... >>> static int copy_backup_region(void) >>> { >>> if (purgatory_backup_dest) { >>> memcpy((void *)purgatory_backup_dest, >>> (void *)purgatory_backup_src, purgatory_backup_sz); >>> } >>> return 0; >>> } >>> ...... >>> >>> arch/x86/kernel/machine_kexec_64.c >>> ...... >>> machine_kexec_prepare()-> >>> arch_update_purgatory()-> >>> ..... >>> >>> Actually, the firs 640k area is encrypted in the first kernel when SME is enabled, here kernel >>> copies the first 640k data to the backup area in purgatory(), because the backup area is mapped >>> as decrypted, this copying operation makes that the first 640k data is decrypted(decoded) and >>> saved to the backup area, but probably kernel can not aware of SME in purgatory(), which causes >>> kernel mistakenly read out the first 640k. >>> >>> In addition, i hacked kernel code as follow: >>> >>> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c >>> index 7bcc92add72c..a51631d36a7a 100644 >>> --- a/fs/proc/vmcore.c >>> +++ b/fs/proc/vmcore.c >>> @@ -377,6 +378,16 @@ static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos, >>> m->offset + m->size - *fpos, >>> buflen); >>> start = m->paddr + *fpos - m->offset; >>> + if (m->paddr == 0x73f60000) {//the backup area's start address:0x73f60000 >>> + tmp = read_from_oldmem(buffer, tsz, &start, >>> + userbuf, false); >>> + } else >>> tmp = read_from_oldmem(buffer, tsz, &start, >>> userbuf, mem_encrypt_active()); >>> if (tmp < 0) >>> >>> Here, i used the crash tool to check the vmcore, i can see that the backup area is decrypted, >>> except for the dma-kmalloc-512. So i suspect that kernel did not correctly read out the first >>> 640k data to backup area. Do you happen to know how to deal with the first 640k area in purgatory() >>> when SME is enabled? Any idea? > > I'm not all that familiar with kexec and purgatory, etc., but I think > that you want to setup the page table that is active when purgatory runs > so that the src and dest both have the SME encryption mask set in their > respective page table entries. This way, when the copy is performed, > everything is copied correctly. Exactly. That's just what i was thinking. > Remember, encrypted data from one page > cannot be directly copied as unencrypted data and decrypted properly in > the new location (e.g. a page of zeroes encrypted at one address will not > appear the same as a page of zeroes encrypted at a different address). Yes, that's right. Thank you, Tom. I'm considering how to solve it, and i guess that probably it needs to properly deal with this problem in purgatory(). Thanks. Lianbo > > Thanks, > Tom > >>> >>> BTW: I' curious the reason why the address of dma-kmalloc-512k always falls into the first 640k >>> region, and i did not see the same issue on another machine. >>> >>> Machine: >>> Serial Number diesel-sys9079-0001 >>> Model AMD Diesel (A0C) >>> CPU AMD EPYC 7601 32-Core Processor >>> >>> >>> Background: >>> On x86_64, the first 640k region is special because of some historical reasons. And kdump kernel will >>> reuse the first 640k region, so kernel will back up(copy) the first 640k region to a backup area in >>> purgatory(), in order not to rewrite the old region(640k) in kdump kernel, which makes sure that kdump >>> can read out the old memory from vmcore. >>> >>> >>> Thanks. >>> Lianbo