From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dennis Kaarsemaker Subject: Re: [PATCH] reflog-walk: don't segfault on non-commit sha1's in the reflog Date: Wed, 30 Dec 2015 22:49:12 +0100 Message-ID: <1451512152.9251.23.camel@kaarsemaker.net> References: <20151230131914.GA27241@lanh> <20151230152245.GA30549@spirit> <1451511208.9251.21.camel@kaarsemaker.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: git@vger.kernel.org, pclouds@gmail.com To: Junio C Hamano X-From: git-owner@vger.kernel.org Wed Dec 30 22:49:21 2015 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1aEOcS-00020a-56 for gcvg-git-2@plane.gmane.org; Wed, 30 Dec 2015 22:49:20 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753993AbbL3VtR (ORCPT ); Wed, 30 Dec 2015 16:49:17 -0500 Received: from mail-wm0-f52.google.com ([74.125.82.52]:32923 "EHLO mail-wm0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751017AbbL3VtP (ORCPT ); Wed, 30 Dec 2015 16:49:15 -0500 Received: by mail-wm0-f52.google.com with SMTP id f206so78028845wmf.0 for ; Wed, 30 Dec 2015 13:49:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kaarsemaker-net.20150623.gappssmtp.com; s=20150623; h=message-id:subject:from:to:cc:date:in-reply-to:references :content-type:mime-version:content-transfer-encoding; bh=giOpflP4boO8lT+T0xsxPij87ylIGxP/eh4/GAvtLnw=; b=QVEckgUITRvsAHCpXqjVXmHncIPIhD+iofngTxE4zVxC6xIzR6YPqU3U7LSKB2zqE6 Z5uo8JM0doxYY6XPQNGtklxyc6/cf/79kvYQgrV4S3RTxnJolKhN7FgIvcgg2jcn4+Ia RO73G/weJS5N0OdzQtNTAleCtKozP2iAUgAo/KFvrGwouIh+QOlripbTb7kzjAFMAk5k i0RpuA2DQrOjgQYaxs6o7IgHXWOio6GzAsxWMjL/vF2lqDanBcytLQgaKC1q/Dh05Rgh 15q5IHUABoEw9jNWIC6mXqPzzs8X/CifT4dtp4ywi7dIV8eehdO817pNJx9VBOlSJqjN iKsg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:content-type:mime-version:content-transfer-encoding; bh=giOpflP4boO8lT+T0xsxPij87ylIGxP/eh4/GAvtLnw=; b=D8iKzke3mWtCPi6bYrXOcyU80Vzo1dbExc75abGspV64eWeGL3CNZdAwmAjq9PlKgL /94WQAF6X05uKJxN/bYZucpXJf6wB8LZTgs8fH8QP+GkKbG9+A2QFXfK3FT7KpzI9UzQ ZNSWlmMClP8lVLCL/PBI7dvyx8buCjw6csT5oU8JSJiuMAayHZCEI7t72XjmX8mf50ET ud/EZSaRTZjkMfjuiktsGThww+TeepKmH9bSCorzP8PTWg1OrjkO5Hvso9Rv1e8UMyXC n7iOYz+bbFkIys9qeme4PsofGcDL8wTa7XMQF4MOvdwlSyc6tfjv7lesLyP9nvRxZFR0 T/Ww== X-Gm-Message-State: ALoCoQkR4AwvNBmcIOWlVV8s9kEQV3a2fDz6GUfAKgspXhtggk8Sd8uN71iIL/LbekCNCPfQpilsq/qK5/k4B/wYaX75ZgHe1A== X-Received: by 10.28.187.198 with SMTP id l189mr59160330wmf.89.1451512154388; Wed, 30 Dec 2015 13:49:14 -0800 (PST) Received: from spirit.home.kaarsemaker.net ([145.132.209.114]) by smtp.gmail.com with ESMTPSA id w194sm12520874wmd.0.2015.12.30.13.49.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Dec 2015 13:49:13 -0800 (PST) In-Reply-To: X-Mailer: Evolution 3.16.5-1ubuntu3.1 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On wo, 2015-12-30 at 13:41 -0800, Junio C Hamano wrote: > Dennis Kaarsemaker writes: > > > On wo, 2015-12-30 at 13:20 -0800, Junio C Hamano wrote: > > > Dennis Kaarsemaker writes: > > > > > > > diff --git a/reflog-walk.c b/reflog-walk.c > > > > index 85b8a54..b85c8e8 100644 > > > > --- a/reflog-walk.c > > > > +++ b/reflog-walk.c > > > > @@ -236,8 +236,8 @@ void fake_reflog_parent(struct > > > > reflog_walk_info > > > > *info, struct commit *commit) > > > > reflog = &commit_reflog->reflogs->items[commit_reflog > > > > ->recno]; > > > > info->last_commit_reflog = commit_reflog; > > > > commit_reflog->recno--; > > > > - commit_info->commit = (struct commit > > > > *)parse_object(reflog > > > > ->osha1); > > > > - if (!commit_info->commit) { > > > > + commit_info->commit = lookup_commit(reflog->osha1); > > > > + if (!commit_info->commit || parse_commit(commit_info > > > > ->commit)) { > > > > commit->parents = NULL; > > > > return; > > > > > > This looks somewhat roundabout and illogical. The original was > > > bad > > > because it blindly assumed reflgo->osha1 refers to a commit > > > without > > > making sure that assumption holds. Calling lookup_commit() > > > blindly > > > is not much better, even though you are helped that the function > > > happens not to barf if the given object is not a commit. > > > > > > Also this changes semantics, no? Trace the original flow and > > > think > > > what happens, when we see a commit object that cannot be parsed > > > in > > > parse_commit_buffer(). parse_object() calls > > > parse_object_buffer() > > > which in turn calls parse_commit_buffer() and the entire > > > callchain > > > returns NULL. commit_info->commit will become NULL in such a > > > case. > > > > > > With your code, lookup_commit() will store a non NULL in > > > commit_info->commit, and parse_commit() calls > > > parse_commit_buffer() > > > and that would fail, so you clear commit->parents to NULL but > > > fail > > > to set commit_info->commit to NULL. > > > > > > Why not keep the parse_object() as-is and make sure we error out > > > unless the result is a commit with a more explicit check, perhaps > > > like this, instead? > > > > lookup_commit actually returns NULL (via object_as_type) for > > objects > > that are not commits, so I don't think the above is true. > > I think you did not read what you are responding to. I was talking > about the error case where the object _is_ a commit (hence lookup > returns it), but parse_commit_buffer() does not like its contents. I read it, but misunderstood it. Thanks for clarifying. > > The code below also loses the diagnostic message about the object > > not being a commit. > > Giving such a diagnostic message is a BUG. > > A ref can legitimately point at any type of object (only refs under > refs/heads/, aka "branches", must point at commits), so you MUST NOT > complain about seeing a non-commit in a reflog in general. Yeah, that makes sense, didn't think of that. -- Dennis Kaarsemaker www.kaarsemaker.net