Re: [PATCH v3] reflog-walk: don't segfault on non-commit sha1's in the reflog
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Dec 31, 2015, 00:02 UTC
- Message-ID
- <xmqq37ujcwny.fsf@gitster.mtv.corp.google.com>
- In-Reply-To
- <20151230233301.GA9194@spirit>
Dennis Kaarsemaker <dennis@kaarsemaker.net> writes:
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> 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.
Show 9 quoted lines
> 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...
Show 19 quoted lines
> 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; > }
Show 21 quoted lines
> + 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?
Show 7 quoted lines
> + git reflog refs/tests/tree-in-reflog >actual && > + test_line_count = 2 actual > +' > + > test_done > -- > 2.7.0-rc1-207-ga35084c