From: Patrick Steinhardt <ps@pks.im>
Date: Mon, 10 Aug 2026 06:17:52 GMT
Subject: Re: [PATCH v2] object-name: avoid use-after-free in get_oid_with_context_1()
Message-ID: <anltEAohp3F9Jbx5@pks.im>
In-Reply-To: <20260809194212.77439-1-diy2903@gmail.com>

On Mon, Aug 10, 2026 at 01:12:09AM +0530, Shlok Kulshreshtha wrote:
> diff --git a/object-name.c b/object-name.c
> index 83efba0ba6..bffe795830 100644
> --- a/object-name.c
> +++ b/object-name.c
> @@ -1803,13 +1803,16 @@ static enum get_oid_result get_oid_with_context_1(struct repository *repo,
>  			    memcmp(ce->name, cp, namelen))
>  				break;
>  			if (ce_stage(ce) == stage) {
> +				int ret = -1;
> +
> +				if (!reject_tree_in_index(repo, only_to_die, ce,
> +							  stage, prefix, cp)) {
> +					oidcpy(oid, &ce->oid);
> +					oc->mode = ce->ce_mode;
> +					ret = 0;
> +				}

The function only ever returns `-1` or `0` itself, so we could've
written it this way:


	int ret = reject_tree_in_index(repo, only_to_die, ce,
				       stage, prefix, cp);
	if (!ret) {
		oidcpy(oid, &ce->oid);
		oc->mode = ce->ce_mode;
	}

	free(new_path);
	return ret;

But I won't insist on that change, this is already a clear improvement.

> diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
> index 4140c4d8ef..e88946c254 100755
> --- a/t/t1092-sparse-checkout-compatibility.sh
> +++ b/t/t1092-sparse-checkout-compatibility.sh
> @@ -1357,6 +1357,17 @@ do
>  	"
>  done
>  
> +test_expect_success 'relative path to a sparse directory' '
> +	init_repos &&
> +
> +	# A ":<stage>:<path>" argument whose path is relative is resolved
> +	# into a heap-allocated buffer, and a sparse directory found at that
> +	# path is reported through it.  Cover that combination, so that the
> +	# reporting does not read the buffer after it has been released.
> +	test_sparse_match test_must_fail git show :0:./folder1/ &&
> +	test_sparse_match test_must_fail git rev-parse :0:./folder1/
> +'

Yup, this test indeed catches the bug:

    --- sparse-checkout-err	2026-08-10 06:13:59.698011294 +0000
    +++ sparse-index-err	2026-08-10 06:13:59.703981906 +0000
    @@ -1 +1 @@
    -fatal: path 'folder1/' does not exist (neither on disk nor in the index)
    +fatal: path '�[UU?' does not exist (neither on disk nor in the index)

Overall this looks good to me, thanks!

Patrick