From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f176.google.com (mail-ig0-f176.google.com [209.85.213.176]) by kanga.kvack.org (Postfix) with ESMTP id 04A066B0038 for ; Tue, 8 Sep 2015 08:18:52 -0400 (EDT) Received: by igbni9 with SMTP id ni9so75344847igb.0 for ; Tue, 08 Sep 2015 05:18:51 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [119.145.14.66]) by mx.google.com with ESMTPS id v11si5186614pdi.230.2015.09.08.05.18.50 for (version=TLS1 cipher=RC4-SHA bits=128/128); Tue, 08 Sep 2015 05:18:51 -0700 (PDT) Message-ID: <55EED09E.3010107@huawei.com> Date: Tue, 8 Sep 2015 20:12:14 +0800 From: Xishi Qiu MIME-Version: 1.0 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 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Andrey Konovalov , Rusty Russell , Michal Marek , zhongjiang@huawei.com Cc: Linux MM , LKML 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 -- 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