From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754703AbbIHMSO (ORCPT ); Tue, 8 Sep 2015 08:18:14 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:60672 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754189AbbIHMRn (ORCPT ); Tue, 8 Sep 2015 08:17:43 -0400 Message-ID: <55EED09E.3010107@huawei.com> Date: Tue, 8 Sep 2015 20:12:14 +0800 From: Xishi Qiu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Andrew Morton , Andrey Konovalov , Rusty Russell , Michal Marek , CC: Linux MM , LKML Subject: [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.25.179] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020206.55EED0A8.0300,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: a38eb41147421ad116eeb0a24e407a39 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The shadow which correspond 16 bytes memory may span 2 or 3 bytes. If the memory is aligned on 8, then the shadow takes only 2 bytes. So we check "shadow_first_bytes" is enough, and need not to call "memory_is_poisoned_1(addr + 15);". But the code "if (likely(!last_byte))" is wrong judgement. e.g. addr=0, so last_byte = 15 & KASAN_SHADOW_MASK = 7, then the code will continue to call "memory_is_poisoned_1(addr + 15);" Signed-off-by: Xishi Qiu --- mm/kasan/kasan.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 7b28e9c..8da2114 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -135,12 +135,11 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) if (unlikely(*shadow_addr)) { u16 shadow_first_bytes = *(u16 *)shadow_addr; - s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK; if (unlikely(shadow_first_bytes)) return true; - if (likely(!last_byte)) + if (likely(IS_ALIGNED(addr, 8))) return false; return memory_is_poisoned_1(addr + 15); -- 1.7.1