From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f169.google.com (mail-lb0-f169.google.com [209.85.217.169]) by kanga.kvack.org (Postfix) with ESMTP id 4406D828F3 for ; Mon, 11 Jan 2016 07:50:50 -0500 (EST) Received: by mail-lb0-f169.google.com with SMTP id sv6so245824935lbb.0 for ; Mon, 11 Jan 2016 04:50:50 -0800 (PST) Received: from relay.parallels.com (relay.parallels.com. [195.214.232.42]) by mx.google.com with ESMTPS id h64si33935787lfb.126.2016.01.11.04.50.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Jan 2016 04:50:49 -0800 (PST) From: 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> 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 Sender: owner-linux-mm@kvack.org List-ID: To: Borislav Petkov , Andy Lutomirski , x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Cc: Brian Gerst , Dave Hansen , Linus Torvalds , Oleg Nesterov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrey Ryabinin 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org