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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 26E7EC433B4 for ; Mon, 3 May 2021 14:55:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB663611CB for ; Mon, 3 May 2021 14:55:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230003AbhECO4H (ORCPT ); Mon, 3 May 2021 10:56:07 -0400 Received: from cloud.peff.net ([104.130.231.41]:43162 "EHLO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229596AbhECO4F (ORCPT ); Mon, 3 May 2021 10:56:05 -0400 Received: (qmail 6065 invoked by uid 109); 3 May 2021 14:55:10 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with ESMTP; Mon, 03 May 2021 14:55:10 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 4347 invoked by uid 111); 3 May 2021 14:55:10 -0000 Received: from coredump.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.2) by peff.net (qpsmtpd/0.94) with (TLS_AES_256_GCM_SHA384 encrypted) ESMTPS; Mon, 03 May 2021 10:55:10 -0400 Authentication-Results: peff.net; auth=none Date: Mon, 3 May 2021 10:55:09 -0400 From: Jeff King To: Derrick Stolee Cc: git@vger.kernel.org, Yiyuan guo Subject: Re: [PATCH 3/5] pack-objects: clamp negative window size to 0 Message-ID: References: <3d77d70b-2cc5-4ca9-8753-fa9af5111842@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <3d77d70b-2cc5-4ca9-8753-fa9af5111842@gmail.com> Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Mon, May 03, 2021 at 08:10:24AM -0400, Derrick Stolee wrote: > On 5/1/2021 10:03 AM, Jeff King wrote: > > A negative window size makes no sense, and the code in find_deltas() is > > not prepared to handle it. If you pass "-1", for example, we end up > > generate a 0-length array of "struct unpacked", but our loop assumes it > > has at least one entry in it (and we end up reading garbage memory). > > > > We could complain to the user about this, but it's more forgiving to > > just clamp it to 0, which means "do not find any deltas at all". The > > 0-case is already tested earlier in the script, so we'll make sure this > > does the same thing. > > This seems like a reasonable approach. It takes existing "undefined" > behavior and turns it into well-understood, "defined" behavior. I was on the fence on doing that, or just: if (window < 0) die("sorry dude, negative windows are nonsense"); So if anybody has a strong preference, I could be easily persuaded. Part of what led me to being forgiving was that we similarly clamp too-large depth values (with a warning; I didn't think it was really necessary here, though). -Peff