From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:59146 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751333AbeAENg3 (ORCPT ); Fri, 5 Jan 2018 08:36:29 -0500 Subject: Patch "x86/kasan: Clear kasan_zero_page after TLB flush" has been added to the 4.4-stable tree To: aryabinin@virtuozzo.com, akpm@linux-foundation.org, bp@alien8.de, bp@suse.de, brgerst@gmail.com, dave.hansen@linux.intel.com, dvlasenk@redhat.com, gregkh@linuxfoundation.org, hpa@zytor.com, jamie.iles@oracle.com, luto@amacapital.net, luto@kernel.org, mcgrof@suse.com, mingo@kernel.org, oleg@redhat.com, peterz@infradead.org, tglx@linutronix.de, torvalds@linux-foundation.org, toshi.kani@hp.com Cc: , From: Date: Fri, 05 Jan 2018 14:36:33 +0100 Message-ID: <151515939361221@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled x86/kasan: Clear kasan_zero_page after TLB flush to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-kasan-clear-kasan_zero_page-after-tlb-flush.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 69e0210fd01ff157d332102219aaf5c26ca8069b Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Mon, 11 Jan 2016 15:51:18 +0300 Subject: x86/kasan: Clear kasan_zero_page after TLB flush From: Andrey Ryabinin commit 69e0210fd01ff157d332102219aaf5c26ca8069b upstream. 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 Cc: Jamie Iles Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/kasan_init_64.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -121,11 +121,16 @@ 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"); } Patches currently in stable-queue which might be from aryabinin@virtuozzo.com are queue-4.4/x86-kasan-clear-kasan_zero_page-after-tlb-flush.patch queue-4.4/x86-boot-add-early-cmdline-parsing-for-options-with-arguments.patch