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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 416FDC0044D for ; Wed, 11 Mar 2020 23:38:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2055520756 for ; Wed, 11 Mar 2020 23:38:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="fRsZjvD6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2055520756 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7443A6B0005; Wed, 11 Mar 2020 19:38:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6F4726B0006; Wed, 11 Mar 2020 19:38:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 60A316B0007; Wed, 11 Mar 2020 19:38:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0033.hostedemail.com [216.40.44.33]) by kanga.kvack.org (Postfix) with ESMTP id 447926B0005 for ; Wed, 11 Mar 2020 19:38:03 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 02E3A812D for ; Wed, 11 Mar 2020 23:38:03 +0000 (UTC) X-FDA: 76584696804.17.alarm74_80704662f061b X-HE-Tag: alarm74_80704662f061b X-Filterd-Recvd-Size: 3118 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Wed, 11 Mar 2020 23:38:02 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 61D4A20754; Wed, 11 Mar 2020 23:38:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583969881; bh=tYse/b2VgvRrHBIlQlCMRUOHJDMPsP7MDl/1tT5CHKA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fRsZjvD6guoPFk2BEwdeTGQoG+yB0UFjHX5rYzIeElepPrrkmGa8tHDNkI/3bJcjw c6HaCi4KjYzlUuyPlnw5PKl3e2cpomqfzDKAFyF0Ka8sRL4rq/8GhcXDVckxbfx5x/ ++T4pZu93SiPDvEq388UoOwzyE2RnNP1+OiqA2Z0= Date: Wed, 11 Mar 2020 16:38:00 -0700 From: Andrew Morton To: Walter Wu Cc: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Qian Cai , Stephen Rothwell , , , , , wsd_upstream Subject: Re: [PATCH -next] kasan: fix -Wstringop-overflow warning Message-Id: <20200311163800.a264d4ec8f26cca7bb5046fb@linux-foundation.org> In-Reply-To: <20200311134244.13016-1-walter-zh.wu@mediatek.com> References: <20200311134244.13016-1-walter-zh.wu@mediatek.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 11 Mar 2020 21:42:44 +0800 Walter Wu wrote: > Compiling with gcc-9.2.1 points out below warnings. > > In function 'memmove', > inlined from 'kmalloc_memmove_invalid_size' at lib/test_kasan.c:301:2: > include/linux/string.h:441:9: warning: '__builtin_memmove' specified > bound 18446744073709551614 exceeds maximum object size > 9223372036854775807 [-Wstringop-overflow=] > > Why generate this warnings? > Because our test function deliberately pass a negative number in memmove(), > so we need to make it "volatile" so that compiler doesn't see it. > > ... > > --- a/lib/test_kasan.c > +++ b/lib/test_kasan.c > @@ -289,6 +289,7 @@ static noinline void __init kmalloc_memmove_invalid_size(void) > { > char *ptr; > size_t size = 64; > + volatile size_t invalid_size = -2; > > pr_info("invalid size in memmove\n"); > ptr = kmalloc(size, GFP_KERNEL); > @@ -298,7 +299,7 @@ static noinline void __init kmalloc_memmove_invalid_size(void) > } > > memset((char *)ptr, 0, 64); > - memmove((char *)ptr, (char *)ptr + 4, -2); > + memmove((char *)ptr, (char *)ptr + 4, invalid_size); > kfree(ptr); > } Huh. Why does this trick suppress the warning? Do we have any guarantee that this it will contiue to work in future gcc's?