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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AD684EB64DD for ; Tue, 1 Aug 2023 06:59:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231941AbjHAG7l (ORCPT ); Tue, 1 Aug 2023 02:59:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60094 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229675AbjHAG7k (ORCPT ); Tue, 1 Aug 2023 02:59:40 -0400 Received: from 1wt.eu (ded1.1wt.eu [163.172.96.212]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 48A591BD; Mon, 31 Jul 2023 23:59:39 -0700 (PDT) Received: (from willy@localhost) by mail.home.local (8.17.1/8.17.1/Submit) id 3716xHHu030364; Tue, 1 Aug 2023 08:59:17 +0200 Date: Tue, 1 Aug 2023 08:59:17 +0200 From: Willy Tarreau To: Thomas =?iso-8859-1?Q?Wei=DFschuh?= Cc: Shuah Khan , linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Yuan Tan , Zhangjin Wu Subject: Re: [PATCH v2 09/10] selftests/nolibc: test return value of read() in test_vfprintf Message-ID: References: <20230801-nolibc-warnings-v2-0-1ba5ca57bd9b@weissschuh.net> <20230801-nolibc-warnings-v2-9-1ba5ca57bd9b@weissschuh.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230801-nolibc-warnings-v2-9-1ba5ca57bd9b@weissschuh.net> Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Tue, Aug 01, 2023 at 07:30:16AM +0200, Thomas Weißschuh wrote: > If read() fails and returns -1 buf would be accessed out of bounds. > > Signed-off-by: Thomas Weißschuh > --- > tools/testing/selftests/nolibc/nolibc-test.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c > index 82714051c72f..a334f8450a34 100644 > --- a/tools/testing/selftests/nolibc/nolibc-test.c > +++ b/tools/testing/selftests/nolibc/nolibc-test.c > @@ -1031,6 +1031,12 @@ static int expect_vfprintf(int llen, int c, const char *expected, const char *fm > lseek(fd, 0, SEEK_SET); > > r = read(fd, buf, sizeof(buf) - 1); > + if (r == -1) { > + llen += printf(" read() = %s", errorname(errno)); > + result(llen, FAIL); > + return 1; > + } > + > buf[r] = '\0'; In fact given the nature of this file (test if we properly implemented our syscalls), I think that a more conservative approach is deserved because if we messed up on read() we can have anything on return and we don't want to trust that. As such I would suggest that we declare r as ssize_t and verify that it's neither negative nor larger than sizeof(buf)-1, which becomes: if ((size_t)r >= sizeof(buf)) { ... fail ... } You'll also have to turn w to ssize_t then due to the test later BTW. Willy