git@vger.kernel.org list mirror (unofficial, one of many)
 help / color / mirror / code / Atom feed
From: Jeff King <peff@peff.net>
To: "Martin Ågren" <martin.agren@gmail.com>
Cc: git@vger.kernel.org, "brian m . carlson" <sandals@crustytoothpaste.net>
Subject: Re: [PATCH v2 2/3] setup: do not use invalid `repository_format`
Date: Tue, 15 Jan 2019 14:31:13 -0500	[thread overview]
Message-ID: <20190115193112.GE4886@sigill.intra.peff.net> (raw)
In-Reply-To: <a7e58385290e6789105d2d5b794f4bf8607285dd.1547488709.git.martin.agren@gmail.com>

On Mon, Jan 14, 2019 at 07:34:56PM +0100, Martin Ågren wrote:

> If `read_repository_format()` encounters an error, `format->version`
> will be -1 and all other fields of `format` will be undefined. However,
> in `setup_git_directory_gently()`, we use `repo_fmt.hash_algo`
> regardless of the value of `repo_fmt.version`.
> 
> This can be observed by adding this to the end of
> `read_repository_format()`:
> 
> 	if (format->version == -1)
> 		format->hash_algo = 0; /* no-one should peek at this! */
> 
> This causes, e.g., "git branch -m q q2 without config should succeed" in
> t3200 to fail with "fatal: Failed to resolve HEAD as a valid ref."
> because it has moved .git/config out of the way and is now trying to use
> a bad hash algorithm.
> 
> Check that `version` is non-negative before using `hash_algo`.
> 
> This patch adds no tests, but do note that if we skip this patch, the
> next patch would cause existing tests to fail as outlined above.

I'm still somewhat confused about how this breaks. If we move
".git/config" out of the way, then we have no version indicator and
presumably we should guess GIT_HASH_SHA1. Which is what's happening if
we fail to call repo_set_hash_algo(), no?  In other words, wouldn't
repo_set_hash_algo() always be a noop in that case?

I get why adding the code snippet above would cause that assumption to
break, but I am just not sure why we would add that code snippet. ;)

I also get why read_repository_format() doing this in patch 3 would be a
problem:

  +       if (format->version == -1) {
  +               clear_repository_format(format);
  +               format->version = -1;
  +       }

but doesn't that point out that clear_repository_format() should be
setting hash_algo to GIT_HASH_SHA1 as the default (and likewise "bare =
-1", etc, that is done in that function)?

-Peff

  reply	other threads:[~2019-01-15 19:31 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-18  7:25 [PATCH 0/3] setup: add `clear_repository_format()` Martin Ågren
2018-12-18  7:25 ` [PATCH 1/3] setup: drop return value from `read_repository_format()` Martin Ågren
2018-12-19 15:27   ` Jeff King
2018-12-19 21:42     ` Martin Ågren
2018-12-20  0:17     ` brian m. carlson
2018-12-20  2:52       ` Jeff King
2018-12-20  3:45         ` brian m. carlson
2018-12-20 14:53           ` Jeff King
2018-12-18  7:25 ` [PATCH 2/3] setup: do not use invalid `repository_format` Martin Ågren
2018-12-19  0:18   ` brian m. carlson
2018-12-19 21:43     ` Martin Ågren
2018-12-19 15:38   ` Jeff King
2018-12-19 21:46     ` Martin Ågren
2018-12-19 23:17       ` Jeff King
2018-12-20  0:21     ` brian m. carlson
2018-12-18  7:25 ` [PATCH 3/3] setup: add `clear_repository_format()` Martin Ågren
2018-12-19 15:48   ` Jeff King
2018-12-19 21:49     ` Martin Ågren
2019-01-14 18:34 ` [PATCH v2 0/3] " Martin Ågren
2019-01-14 18:34   ` [PATCH v2 1/3] setup: free old value before setting `work_tree` Martin Ågren
2019-01-14 18:34   ` [PATCH v2 2/3] setup: do not use invalid `repository_format` Martin Ågren
2019-01-15 19:31     ` Jeff King [this message]
2019-01-17  6:31       ` Martin Ågren
2019-01-22  7:07         ` Jeff King
2019-01-22 13:34           ` Martin Ågren
2019-01-22 21:45             ` [PATCH v3 0/2] setup: fix memory leaks with `struct repository_format` Martin Ågren
2019-01-22 21:45               ` [PATCH v3 1/2] setup: free old value before setting `work_tree` Martin Ågren
2019-01-22 21:45               ` [PATCH v3 2/2] setup: fix memory leaks with `struct repository_format` Martin Ågren
2019-01-23  5:57                 ` Jeff King
2019-01-24  0:14                   ` brian m. carlson
2019-01-25 19:25                     ` Martin Ågren
2019-01-25 19:24                   ` Martin Ågren
2019-01-25 19:51                     ` Jeff King
2019-02-25 19:21                       ` Martin Ågren
2019-02-26 17:46                         ` Jeff King
2019-02-28 20:36                           ` [PATCH v4 0/2] " Martin Ågren
2019-02-28 20:36                             ` [PATCH v4 1/2] setup: free old value before setting `work_tree` Martin Ågren
2019-02-28 20:36                             ` [PATCH v4 2/2] setup: fix memory leaks with `struct repository_format` Martin Ågren
2019-03-06  4:56                             ` [PATCH v4 0/2] " Jeff King
2019-01-14 18:34   ` [PATCH v2 3/3] setup: add `clear_repository_format()` Martin Ågren

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190115193112.GE4886@sigill.intra.peff.net \
    --to=peff@peff.net \
    --cc=git@vger.kernel.org \
    --cc=martin.agren@gmail.com \
    --cc=sandals@crustytoothpaste.net \
    --subject='Re: [PATCH v2 2/3] setup: do not use invalid `repository_format`' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

git@vger.kernel.org list mirror (unofficial, one of many)

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://public-inbox.org/git
	git clone --mirror http://ou63pmih66umazou.onion/git
	git clone --mirror http://czquwvybam4bgbro.onion/git
	git clone --mirror http://hjrcffqmbrq6wope.onion/git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V1 git git/ https://public-inbox.org/git \
		git@vger.kernel.org
	public-inbox-index git

Example config snippet for mirrors.
Newsgroups are available over NNTP:
	nntp://news.public-inbox.org/inbox.comp.version-control.git
	nntp://7fh6tueqddpjyxjmgtdiueylzoqt6pt7hec3pukyptlmohoowvhde4yd.onion/inbox.comp.version-control.git
	nntp://ie5yzdi7fg72h7s4sdcztq5evakq23rdt33mfyfcddc5u3ndnw24ogqd.onion/inbox.comp.version-control.git
	nntp://4uok3hntl7oi7b4uf4rtfwefqeexfzil2w6kgk2jn5z2f764irre7byd.onion/inbox.comp.version-control.git
	nntp://news.gmane.io/gmane.comp.version-control.git
 note: .onion URLs require Tor: https://www.torproject.org/

code repositories for project(s) associated with this inbox:

	https://80x24.org/mirrors/git.git

AGPL code for this site: git clone https://public-inbox.org/public-inbox.git