From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753097AbcEIWXK (ORCPT ); Mon, 9 May 2016 18:23:10 -0400 Received: from mail-vk0-f65.google.com ([209.85.213.65]:34979 "EHLO mail-vk0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751658AbcEIWXI (ORCPT ); Mon, 9 May 2016 18:23:08 -0400 MIME-Version: 1.0 In-Reply-To: References: <1462825332-10505-1-git-send-email-keescook@chromium.org> <1462825332-10505-2-git-send-email-keescook@chromium.org> Date: Mon, 9 May 2016 15:23:06 -0700 X-Google-Sender-Auth: 4ajW9_IPp0eHP0g3J6V_dnOuBLg Message-ID: Subject: Re: [PATCH v7 1/9] x86/KASLR: Initialize mapping_info every time From: Yinghai Lu To: Kees Cook Cc: Ingo Molnar , Borislav Petkov , Baoquan He , Ingo Molnar , "H. Peter Anvin" , Borislav Petkov , Vivek Goyal , Andy Lutomirski , lasse.collin@tukaani.org, Andrew Morton , Dave Young , "kernel-hardening@lists.openwall.com" , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 9, 2016 at 3:01 PM, Yinghai Lu wrote: > On Mon, May 9, 2016 at 1:22 PM, Kees Cook wrote: >> As it turns out, mapping_info DOES need to be initialized every >> time. Without this, page tables were not being corrected updated, which >> could cause reboots when a physical address beyond 2G was chosen. >> >> Signed-off-by: Kees Cook >> --- >> arch/x86/boot/compressed/pagetable.c | 16 +++++----------- >> 1 file changed, 5 insertions(+), 11 deletions(-) >> >> diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c >> index 3c99051566a9..34b95df14e69 100644 >> --- a/arch/x86/boot/compressed/pagetable.c >> +++ b/arch/x86/boot/compressed/pagetable.c >> @@ -90,23 +90,17 @@ static void prepare_level4(void) >> } >> >> /* >> - * Mapping information structure passed to kernel_ident_mapping_init(). >> - * Since this never changes, there's no reason to repeatedly fill it >> - * in on the stack when calling add_identity_map(). >> - */ >> -static struct x86_mapping_info mapping_info = { >> - .alloc_pgt_page = alloc_pgt_page, >> - .context = &pgt_data, >> - .pmd_flag = __PAGE_KERNEL_LARGE_EXEC, >> -}; >> - >> -/* >> * Adds the specified range to what will become the new identity mappings. >> * Once all ranges have been added, the new mapping is activated by calling >> * finalize_identity_maps() below. >> */ >> void add_identity_map(unsigned long start, unsigned long size) >> { >> + struct x86_mapping_info mapping_info = { >> + .alloc_pgt_page = alloc_pgt_page, >> + .context = &pgt_data, >> + .pmd_flag = __PAGE_KERNEL_LARGE_EXEC, >> + }; >> unsigned long end = start + size; > > Still should be assigned once, and should be done in > prepare_level4(). --- by may need different name for that ? > > The exact reason to have assigning in functions. > > pgt_data address could be changed during kernel relocation. > so can not assigned during compiling time. Something like: -/* - * Mapping information structure passed to kernel_ident_mapping_init(). - * Since this never changes, there's no reason to repeatedly fill it - * in on the stack when calling add_identity_map(). - */ -static struct x86_mapping_info mapping_info = { - .alloc_pgt_page = alloc_pgt_page, - .context = &pgt_data, - .pmd_flag = __PAGE_KERNEL_LARGE_EXEC, -}; +static struct x86_mapping_info mapping_info; /* * Adds the specified range to what will become the new identity mappings. @@ -110,8 +101,14 @@ void add_identity_map(unsigned long start, unsigned long size) unsigned long end = start + size; /* Make sure we have a top level page table ready to use. */ - if (!level4p) + if (!level4p) { + /* need to set once during run time */ + mapping_info.alloc_pgt_page = alloc_pgt_page; + mapping_info.context = &pgt_data; + mapping_info.pmd_flag = __PAGE_KERNEL_LARGE_EXEC; + prepare_level4(); + } /* Align boundary to 2M. */ start = round_down(start, PMD_SIZE);