From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757560AbcBIQIP (ORCPT ); Tue, 9 Feb 2016 11:08:15 -0500 Received: from terminus.zytor.com ([198.137.202.10]:38343 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757510AbcBIQIJ (ORCPT ); Tue, 9 Feb 2016 11:08:09 -0500 Date: Tue, 9 Feb 2016 08:06:41 -0800 From: tip-bot for Andrey Ryabinin Message-ID: Cc: oleg@redhat.com, hpa@zytor.com, peterz@infradead.org, luto@kernel.org, tglx@linutronix.de, dave.hansen@linux.intel.com, dvlasenk@redhat.com, bp@alien8.de, mcgrof@suse.com, brgerst@gmail.com, bp@suse.de, mingo@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, luto@amacapital.net, toshi.kani@hp.com, aryabinin@virtuozzo.com, torvalds@linux-foundation.org Reply-To: torvalds@linux-foundation.org, toshi.kani@hp.com, aryabinin@virtuozzo.com, linux-kernel@vger.kernel.org, luto@amacapital.net, bp@suse.de, brgerst@gmail.com, akpm@linux-foundation.org, mingo@kernel.org, dvlasenk@redhat.com, dave.hansen@linux.intel.com, mcgrof@suse.com, bp@alien8.de, peterz@infradead.org, oleg@redhat.com, hpa@zytor.com, tglx@linutronix.de, luto@kernel.org In-Reply-To: <1452516679-32040-2-git-send-email-aryabinin@virtuozzo.com> References: <1452516679-32040-2-git-send-email-aryabinin@virtuozzo.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/mm] x86/kasan: Clear kasan_zero_page after TLB flush Git-Commit-ID: 69e0210fd01ff157d332102219aaf5c26ca8069b X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 69e0210fd01ff157d332102219aaf5c26ca8069b Gitweb: http://git.kernel.org/tip/69e0210fd01ff157d332102219aaf5c26ca8069b Author: Andrey Ryabinin AuthorDate: Mon, 11 Jan 2016 15:51:18 +0300 Committer: Ingo Molnar CommitDate: Tue, 9 Feb 2016 13:33:14 +0100 x86/kasan: Clear kasan_zero_page after TLB flush 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 Reviewed-by: Borislav Petkov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Toshi Kani Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/1452516679-32040-2-git-send-email-aryabinin@virtuozzo.com Signed-off-by: Ingo Molnar --- 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"); }