From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932727AbcAKMuw (ORCPT ); Mon, 11 Jan 2016 07:50:52 -0500 Received: from relay.parallels.com ([195.214.232.42]:55102 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757478AbcAKMut (ORCPT ); Mon, 11 Jan 2016 07:50:49 -0500 From: Andrey Ryabinin To: Borislav Petkov , Andy Lutomirski , , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" CC: Brian Gerst , Dave Hansen , Linus Torvalds , Oleg Nesterov , , , Andrey Ryabinin Subject: [PATCH 1/2] x86/kasan: clear kasan_zero_page after TLB flush Date: Mon, 11 Jan 2016 15:51:18 +0300 Message-ID: <1452516679-32040-2-git-send-email-aryabinin@virtuozzo.com> X-Mailer: git-send-email 2.4.10 In-Reply-To: <1452516679-32040-1-git-send-email-aryabinin@virtuozzo.com> References: <20160110185916.GD22896@pd.tnic> <1452516679-32040-1-git-send-email-aryabinin@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain X-ClientProxiedBy: US-EXCH.sw.swsoft.com (10.255.249.47) To MSK-EXCH1.sw.swsoft.com (10.67.48.55) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently we clear kasan_zero_page before __flush_tlb_all(). This works with current implementation of native_flush_tlb[_global]() because it doesn't cause do any writes to kasan shadow memory. But any subtle change made in native_flush_tlb*() could break this. Also current code seems doesn't work for paravirt guests (lguest). Only after the TLB flush we can be sure that kasan_zero_page is not used as early shadow anymore (instrumented code will not write to it). So it should cleared it only after the TLB flush. Signed-off-by: Andrey Ryabinin --- arch/x86/mm/kasan_init_64.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c index d470cf2..303e470 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -120,11 +120,16 @@ void __init kasan_init(void) kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END), (void *)KASAN_SHADOW_END); - memset(kasan_zero_page, 0, PAGE_SIZE); - load_cr3(init_level4_pgt); __flush_tlb_all(); - init_task.kasan_depth = 0; + /* + * kasan_zero_page has been used as early shadow memory, thus it may + * contain some garbage. Now we can clear it, since after the TLB flush + * no one should write to it. + */ + memset(kasan_zero_page, 0, PAGE_SIZE); + + init_task.kasan_depth = 0; pr_info("KernelAddressSanitizer initialized\n"); } -- 2.4.10