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=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 E8A6EC433F5 for ; Mon, 20 Sep 2021 17:09:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2C8F615E1 for ; Mon, 20 Sep 2021 17:09:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345912AbhITRLB (ORCPT ); Mon, 20 Sep 2021 13:11:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:33538 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345932AbhITRI6 (ORCPT ); Mon, 20 Sep 2021 13:08:58 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D8D4A6139E; Mon, 20 Sep 2021 16:56:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1632156961; bh=zWRyMRxFe1EWlVNwJftPpmD8XfzvNluhmXS0Qz9Tbkk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bifDPxGDCRH5g5DGfZbqr/awBt2AV3yYlo6PJSgE9OOTQYMX6OfJWwtC4AcBpCgoR XethweVO0SPCThxGXyfF5PHfiZnYxhwEUr/GryaPnEz4SWBxE+UspC+dkfKpG4ToH/ XHVVegYqkDjruq472X7EKhGwBOr7i6X7dBj9LW6A= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jiri Olsa , Mike Rapoport , Borislav Petkov , David Hildenbrand , Dave Hansen Subject: [PATCH 4.9 165/175] x86/mm: Fix kern_addr_valid() to cope with existing but not present entries Date: Mon, 20 Sep 2021 18:43:34 +0200 Message-Id: <20210920163923.459567132@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210920163918.068823680@linuxfoundation.org> References: <20210920163918.068823680@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: Mike Rapoport commit 34b1999da935a33be6239226bfa6cd4f704c5c88 upstream. Jiri Olsa reported a fault when running: # cat /proc/kallsyms | grep ksys_read ffffffff8136d580 T ksys_read # objdump -d --start-address=0xffffffff8136d580 --stop-address=0xffffffff8136d590 /proc/kcore /proc/kcore: file format elf64-x86-64 Segmentation fault general protection fault, probably for non-canonical address 0xf887ffcbff000: 0000 [#1] SMP PTI CPU: 12 PID: 1079 Comm: objdump Not tainted 5.14.0-rc5qemu+ #508 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-4.fc34 04/01/2014 RIP: 0010:kern_addr_valid Call Trace: read_kcore ? rcu_read_lock_sched_held ? rcu_read_lock_sched_held ? rcu_read_lock_sched_held ? trace_hardirqs_on ? rcu_read_lock_sched_held ? lock_acquire ? lock_acquire ? rcu_read_lock_sched_held ? lock_acquire ? rcu_read_lock_sched_held ? rcu_read_lock_sched_held ? rcu_read_lock_sched_held ? lock_release ? _raw_spin_unlock ? __handle_mm_fault ? rcu_read_lock_sched_held ? lock_acquire ? rcu_read_lock_sched_held ? lock_release proc_reg_read ? vfs_read vfs_read ksys_read do_syscall_64 entry_SYSCALL_64_after_hwframe The fault happens because kern_addr_valid() dereferences existent but not present PMD in the high kernel mappings. Such PMDs are created when free_kernel_image_pages() frees regions larger than 2Mb. In this case, a part of the freed memory is mapped with PMDs and the set_memory_np_noalias() -> ... -> __change_page_attr() sequence will mark the PMD as not present rather than wipe it completely. Have kern_addr_valid() check whether higher level page table entries are present before trying to dereference them to fix this issue and to avoid similar issues in the future. Stable backporting note: ------------------------ Note that the stable marking is for all active stable branches because there could be cases where pagetable entries exist but are not valid - see 9a14aefc1d28 ("x86: cpa, fix lookup_address"), for example. So make sure to be on the safe side here and use pXY_present() accessors rather than pXY_none() which could #GP when accessing pages in the direct map. Also see: c40a56a7818c ("x86/mm/init: Remove freed kernel image areas from alias mapping") for more info. Reported-by: Jiri Olsa Signed-off-by: Mike Rapoport Signed-off-by: Borislav Petkov Reviewed-by: David Hildenbrand Acked-by: Dave Hansen Tested-by: Jiri Olsa Cc: # 4.4+ Link: https://lkml.kernel.org/r/20210819132717.19358-1-rppt@kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/init_64.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1126,21 +1126,21 @@ int kern_addr_valid(unsigned long addr) return 0; pud = pud_offset(pgd, addr); - if (pud_none(*pud)) + if (!pud_present(*pud)) return 0; if (pud_large(*pud)) return pfn_valid(pud_pfn(*pud)); pmd = pmd_offset(pud, addr); - if (pmd_none(*pmd)) + if (!pmd_present(*pmd)) return 0; if (pmd_large(*pmd)) return pfn_valid(pmd_pfn(*pmd)); pte = pte_offset_kernel(pmd, addr); - if (pte_none(*pte)) + if (!pte_present(*pte)) return 0; return pfn_valid(pte_pfn(*pte));