From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 688AEC432C0 for ; Thu, 21 Nov 2019 13:04:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B6352089D for ; Thu, 21 Nov 2019 13:04:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726961AbfKUNEA (ORCPT ); Thu, 21 Nov 2019 08:04:00 -0500 Received: from relay.sw.ru ([185.231.240.75]:52106 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726293AbfKUND7 (ORCPT ); Thu, 21 Nov 2019 08:03:59 -0500 Received: from dhcp-172-16-25-5.sw.ru ([172.16.25.5]) by relay.sw.ru with esmtp (Exim 4.92.3) (envelope-from ) id 1iXm7i-0002DQ-S4; Thu, 21 Nov 2019 16:03:50 +0300 Subject: Re: [PATCH v4 1/2] kasan: detect negative size in memory operation function To: Walter Wu Cc: Alexander Potapenko , Dmitry Vyukov , Matthias Brugger , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, wsd_upstream , linux-mediatek@lists.infradead.org References: <20191112065302.7015-1-walter-zh.wu@mediatek.com> <040479c3-6f96-91c6-1b1a-9f3e947dac06@virtuozzo.com> <1574341376.8338.4.camel@mtksdccf07> From: Andrey Ryabinin Message-ID: <217bd537-e6b7-3acc-b6bb-ac9c5d94da89@virtuozzo.com> Date: Thu, 21 Nov 2019 16:03:38 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <1574341376.8338.4.camel@mtksdccf07> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/21/19 4:02 PM, Walter Wu wrote: > On Thu, 2019-11-21 at 15:26 +0300, Andrey Ryabinin wrote: >> >> On 11/12/19 9:53 AM, Walter Wu wrote: >> >>> diff --git a/mm/kasan/common.c b/mm/kasan/common.c >>> index 6814d6d6a023..4bfce0af881f 100644 >>> --- a/mm/kasan/common.c >>> +++ b/mm/kasan/common.c >>> @@ -102,7 +102,8 @@ EXPORT_SYMBOL(__kasan_check_write); >>> #undef memset >>> void *memset(void *addr, int c, size_t len) >>> { >>> - check_memory_region((unsigned long)addr, len, true, _RET_IP_); >>> + if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_)) >>> + return NULL; >>> >>> return __memset(addr, c, len); >>> } >>> @@ -110,8 +111,9 @@ void *memset(void *addr, int c, size_t len) >>> #undef memmove >>> void *memmove(void *dest, const void *src, size_t len) >>> { >>> - check_memory_region((unsigned long)src, len, false, _RET_IP_); >>> - check_memory_region((unsigned long)dest, len, true, _RET_IP_); >>> + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || >>> + !check_memory_region((unsigned long)dest, len, true, _RET_IP_)) >>> + return NULL; >>> >>> return __memmove(dest, src, len); >>> } >>> @@ -119,8 +121,9 @@ void *memmove(void *dest, const void *src, size_t len) >>> #undef memcpy >>> void *memcpy(void *dest, const void *src, size_t len) >>> { >>> - check_memory_region((unsigned long)src, len, false, _RET_IP_); >>> - check_memory_region((unsigned long)dest, len, true, _RET_IP_); >>> + if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || >>> + !check_memory_region((unsigned long)dest, len, true, _RET_IP_)) >>> + return NULL; >>> >> >> I realized that we are going a wrong direction here. Entirely skipping mem*() operation on any >> poisoned shadow value might only make things worse. Some bugs just don't have any serious consequences, >> but skipping the mem*() ops entirely might introduce such consequences, which wouldn't happen otherwise. >> >> So let's keep this code as this, no need to check the result of check_memory_region(). >> >> > Ok, we just need to determine whether size is negative number. If yes > then KASAN produce report and continue to execute mem*(). right? > Yes.