From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753612AbcFOTFu (ORCPT ); Wed, 15 Jun 2016 15:05:50 -0400 Received: from mail-pf0-f170.google.com ([209.85.192.170]:36833 "EHLO mail-pf0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751591AbcFOTFr (ORCPT ); Wed, 15 Jun 2016 15:05:47 -0400 Date: Wed, 15 Jun 2016 12:05:45 -0700 From: Kees Cook To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Thomas Garnier , x86@kernel.org, Borislav Petkov , Matt Fleming , Toshi Kani , Sai Praneeth , Dexuan Cui , Christian Borntraeger , Chris Wilson Subject: [PATCH] x86/mm: Do not reference phys addr beyond kernel Message-ID: <20160615190545.GA26071@www.outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Garnier The new physical address randomized KASLR implementation can cause the kernel to be aligned close to the end of physical memory. In this case, _brk_end aligned to PMD will go beyond what is expected safe and hit the assert in __phys_addr_symbol(): VIRTUAL_BUG_ON(y >= KERNEL_IMAGE_SIZE); Instead, perform an inclusive range check to avoid incorrectly triggering the assert: kernel BUG at arch/x86/mm/physaddr.c:38! invalid opcode: 0000 [#1] SMP ... RIP: 0010:[] __phys_addr_symbol+0x41/0x50 ... Call Trace: [] cpa_process_alias+0xa9/0x210 [] ? do_raw_spin_unlock+0xc1/0x100 [] __change_page_attr_set_clr+0x8cf/0xbd0 [] ? vm_unmap_aliases+0x7d/0x210 [] change_page_attr_set_clr+0x18c/0x4e0 [] set_memory_4k+0x2c/0x40 [] check_bugs+0x28/0x2a [] start_kernel+0x49d/0x4b9 [] ? early_idt_handler_array+0x120/0x120 [] x86_64_start_reservations+0x29/0x2b [] x86_64_start_kernel+0x143/0x152 Signed-off-by: Thomas Garnier Signed-off-by: Kees Cook --- Needed before the KASLR improvement series can be finished. --- arch/x86/mm/pageattr.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 7a1f7bbf4105..379b5111ac6b 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -101,7 +101,8 @@ static inline unsigned long highmap_start_pfn(void) static inline unsigned long highmap_end_pfn(void) { - return __pa_symbol(roundup(_brk_end, PMD_SIZE)) >> PAGE_SHIFT; + /* Do not reference physical address outside the kernel. */ + return __pa_symbol(roundup(_brk_end, PMD_SIZE) - 1) >> PAGE_SHIFT; } #endif @@ -112,6 +113,12 @@ within(unsigned long addr, unsigned long start, unsigned long end) return addr >= start && addr < end; } +static inline int +within_inclusive(unsigned long addr, unsigned long start, unsigned long end) +{ + return addr >= start && addr <= end; +} + /* * Flushing functions */ @@ -1316,7 +1323,8 @@ static int cpa_process_alias(struct cpa_data *cpa) * to touch the high mapped kernel as well: */ if (!within(vaddr, (unsigned long)_text, _brk_end) && - within(cpa->pfn, highmap_start_pfn(), highmap_end_pfn())) { + within_inclusive(cpa->pfn, highmap_start_pfn(), + highmap_end_pfn())) { unsigned long temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) + __START_KERNEL_map - phys_base; alias_cpa = *cpa; -- 2.7.4 -- Kees Cook Chrome OS & Brillo Security