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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 617A8C4360F for ; Tue, 2 Apr 2019 16:13:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 30D51206BA for ; Tue, 2 Apr 2019 16:13:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730612AbfDBQNk (ORCPT ); Tue, 2 Apr 2019 12:13:40 -0400 Received: from relay.sw.ru ([185.231.240.75]:60910 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729384AbfDBQNi (ORCPT ); Tue, 2 Apr 2019 12:13:38 -0400 Received: from [172.16.25.12] by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1hBM2U-00028a-GG; Tue, 02 Apr 2019 19:13:30 +0300 Subject: Re: [RFC PATCH v2 3/3] kasan: add interceptors for all string functions To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Nicholas Piggin , "Aneesh Kumar K.V" , Alexander Potapenko , Dmitry Vyukov , Daniel Axtens Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com References: <51a6d9d7185de310f37ccbd7e4ebfdd6c7e9791f.1553785020.git.christophe.leroy@c-s.fr> <3211b0f8-7b52-01b7-8208-65d746969248@c-s.fr> From: Andrey Ryabinin Message-ID: Date: Tue, 2 Apr 2019 19:14:02 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <3211b0f8-7b52-01b7-8208-65d746969248@c-s.fr> 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 4/2/19 12:43 PM, Christophe Leroy wrote: > Hi Dmitry, Andrey and others, > > Do you have any comments to this series ? > I don't see justification for adding all these non-instrumented functions. We need only some subset of these functions and only on powerpc so far. Arches that don't use str*() that early simply doesn't need not-instrumented __str*() variant. Also I don't think that auto-replace str* to __str* for all not instrumented files is a good idea, as this will reduce KASAN coverage. E.g. we don't instrument slub.c but there is no reason to use non-instrumented __str*() functions there. And finally, this series make bug reporting slightly worse. E.g. let's look at strcpy(): +char *strcpy(char *dest, const char *src) +{ + size_t len = __strlen(src) + 1; + + check_memory_region((unsigned long)src, len, false, _RET_IP_); + check_memory_region((unsigned long)dest, len, true, _RET_IP_); + + return __strcpy(dest, src); +} If src is not-null terminated string we might not see proper out-of-bounds report from KASAN only a crash in __strlen(). Which might make harder to identify where 'src' comes from, where it was allocated and what's the size of allocated area. > I'd like to know if this approach is ok or if it is better to keep doing as in https://patchwork.ozlabs.org/patch/1055788/ > I think the patch from link is a better solution to the problem.