From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752766AbcEJVKf (ORCPT ); Tue, 10 May 2016 17:10:35 -0400 Received: from mail.kernel.org ([198.145.29.136]:47103 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751466AbcEJVKe (ORCPT ); Tue, 10 May 2016 17:10:34 -0400 From: Andy Lutomirski To: x86@kernel.org Cc: Cyrill Gorcunov , Dmitry Safonov <0x7f454c46@gmail.com>, Ruslan Kabatsayev , Borislav Petkov , Pavel Emelyanov , Oleg Nesterov , linux-kernel@vger.kernel.org, Andy Lutomirski Subject: [PATCH] x86/mm: Switch from TASK_SIZE to TASK_SIZE_MAX in the page fault code Date: Tue, 10 May 2016 14:10:29 -0700 Message-Id: <1242fb23b0d05c3069dbf5758ac55d26bc114bef.1462914565.git.luto@kernel.org> X-Mailer: git-send-email 2.5.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org x86's page fault handlers had two TASK_SIZE uses that should have been TASK_SIZE_MAX. I don't think that either one had a visible effect, but this makes the code clearer and should save a few bytes of text. (And I eventually want to eradicate TASK_SIZE. This will help.) Reported-by: Cyrill Gorcunov Signed-off-by: Andy Lutomirski --- arch/x86/mm/fault.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 1d75b98a8414..45940239b983 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -292,7 +292,7 @@ void vmalloc_sync_all(void) return; for (address = VMALLOC_START & PMD_MASK; - address >= TASK_SIZE && address < FIXADDR_TOP; + address >= TASK_SIZE_MAX && address < FIXADDR_TOP; address += PMD_SIZE) { struct page *page; @@ -854,8 +854,13 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, return; } #endif - /* Kernel addresses are always protection faults: */ - if (address >= TASK_SIZE) + + /* + * To avoid leaking information about the kernel page table + * layout, pretend that user-mode accesses to kernel addresses + * are always protection faults. + */ + if (address >= TASK_SIZE_MAX) error_code |= PF_PROT; if (likely(show_unhandled_signals)) -- 2.5.5