From: Junio C Hamano <gitster@pobox•com>
To: Dennis Kaarsemaker <dennis@kaarsemaker•net>
Cc: git@vger•kernel.org, pclouds@gmail•com
Subject: Re: [PATCH v3] reflog-walk: don't segfault on non-commit sha1's in the reflog
Date: Wed, 30 Dec 2015 16:02:41 -0800 [thread overview]
Message-ID: <xmqq37ujcwny.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20151230233301.GA9194@spirit> (Dennis Kaarsemaker's message of "Thu, 31 Dec 2015 00:33:03 +0100")
Dennis Kaarsemaker <dennis@kaarsemaker•net> writes:
> This turned out to be doable in the same code segment: just keep on
> processing reflog entries until you hit a commit or run out of entries.
> That (and the updated foremerly-failing test) are the only changes
> between v2 and v3.
>
> I'll try to actually implement the proper solution, but that'll take a
> while. Until then, this at least stops a segfault :)
Yeah, that would be an ambitious project.
> diff --git a/reflog-walk.c b/reflog-walk.c
> index 85b8a54..0ebd1da 100644
> --- a/reflog-walk.c
> +++ b/reflog-walk.c
> @@ -221,6 +221,7 @@ void fake_reflog_parent(struct reflog_walk_info *info, struct commit *commit)
> struct commit_info *commit_info =
> get_commit_info(commit, &info->reflogs, 0);
> struct commit_reflog *commit_reflog;
> + struct object *logobj;
This thing is not initialized...
> struct reflog_info *reflog;
>
> info->last_commit_reflog = NULL;
> @@ -232,15 +233,20 @@ void fake_reflog_parent(struct reflog_walk_info *info, struct commit *commit)
> commit->parents = NULL;
> return;
> }
> -
> - 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) {
> +
> + do {
> + reflog = &commit_reflog->reflogs->items[commit_reflog->recno];
> + commit_reflog->recno--;
> + logobj = parse_object(reflog->osha1);
> + } while (commit_reflog->recno && (logobj && logobj->type != OBJ_COMMIT));
But this loop runs at least once, so logobj will always have some
sane value when the loop exits.
> + if (!logobj || logobj->type != OBJ_COMMIT) {
And the only case where this should trigger is when we ran out of
recno. Am I reading the updated code correctly?
With the updated code, the number of times we return from this
function is different from the number initially set to recno. I had
to wonder if the caller cares and misbehaves, but the caller does
not know how long the reflog is before starting to call
get_revision() in a loop anyway, so it already has to deal with a
case where it did .recno=20 and get_revision() did not return that
many times. So this probably is safe.
> + commit_info->commit = NULL;
> commit->parents = NULL;
> return;
> }
> + commit_info->commit = (struct commit *)logobj;
>
> commit->parents = xcalloc(1, sizeof(struct commit_list));
> commit->parents->item = commit_info->commit;
> diff --git a/t/t1410-reflog.sh b/t/t1410-reflog.sh
> index b79049f..f97513c 100755
> --- a/t/t1410-reflog.sh
> +++ b/t/t1410-reflog.sh
> @@ -325,4 +325,17 @@ test_expect_success 'parsing reverse reflogs at BUFSIZ boundaries' '
> test_cmp expect actual
> '
>
> +test_expect_success 'no segfaults for reflog containing non-commit sha1s' '
> + git update-ref --create-reflog -m "Creating ref" \
> + refs/tests/tree-in-reflog HEAD &&
> + git update-ref -m "Forcing tree" refs/tests/tree-in-reflog HEAD^{tree} &&
> + git update-ref -m "Restoring to commit" refs/tests/tree-in-reflog HEAD &&
> + git reflog refs/tests/tree-in-reflog
> +'
> +
> +test_expect_success 'reflog containing non-commit sha1s displays properly' '
In general, "properly" is a poor word to use in test description (or
a commit log message or a bug report, for that matter), as the whole
point of a test is to precisely define what is "proper".
And the code change declares that a proper thing to do is to omit
non-commit entries without segfaulting, so something like
s/displays properly/omits them/
perhaps?
> + git reflog refs/tests/tree-in-reflog >actual &&
> + test_line_count = 2 actual
> +'
> +
> test_done
> --
> 2.7.0-rc1-207-ga35084c
next prev parent reply other threads:[~2015-12-31 0:02 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-30 9:24 Segfault in git reflog Dennis Kaarsemaker
2015-12-30 10:31 ` Duy Nguyen
2015-12-30 11:17 ` Dennis Kaarsemaker
2015-12-30 11:26 ` Duy Nguyen
2015-12-30 11:28 ` Duy Nguyen
2015-12-30 12:28 ` Dennis Kaarsemaker
2015-12-30 13:19 ` Duy Nguyen
2015-12-30 15:22 ` [PATCH] reflog-walk: don't segfault on non-commit sha1's in the reflog Dennis Kaarsemaker
2015-12-30 21:20 ` Junio C Hamano
2015-12-30 21:33 ` Dennis Kaarsemaker
2015-12-30 21:41 ` Junio C Hamano
2015-12-30 21:49 ` Dennis Kaarsemaker
2015-12-30 22:17 ` [PATCH v2] " Dennis Kaarsemaker
2015-12-30 22:42 ` Junio C Hamano
2015-12-30 23:33 ` [PATCH v3] " Dennis Kaarsemaker
2015-12-31 0:02 ` Junio C Hamano [this message]
2015-12-31 8:57 ` Dennis Kaarsemaker
2015-12-31 15:43 ` Dennis Kaarsemaker
2016-01-05 21:12 ` [PATCH v4] " Dennis Kaarsemaker
2016-01-06 1:05 ` Eric Sunshine
2016-01-06 1:20 ` Dennis Kaarsemaker
2016-01-06 1:28 ` Eric Sunshine
2016-01-06 1:52 ` Eric Sunshine
2016-01-06 9:13 ` Dennis Kaarsemaker
2016-01-06 9:30 ` Duy Nguyen
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