Re: [PATCH 3/6] clone: fix a memory leak of the "git_dir" variable

From: Junio C Hamano <gitster@pobox.com>
Date: Oct 22, 2021, 00:07 UTC
Message-ID: <xmqqilxpgbvv.fsf@gitster.g>
In-Reply-To: <patch-3.6-86d928ae2f9-20211021T155529Z-avarab@gmail.com>

Ævar Arnfjörð Bjarmason  <avarab@gmail.com> writes:

Show 25 quoted lines

> At this point in cmd_clone the "git_dir" is always either an
> xstrdup()'d string, or something we got from mkpathdup(). Let's free()
> it before we clobber it.
>
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---
>  builtin/clone.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/builtin/clone.c b/builtin/clone.c
> index 559acf9e036..fb377b27657 100644
> --- a/builtin/clone.c
> +++ b/builtin/clone.c
> @@ -1040,8 +1040,10 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
>  	init_db(git_dir, real_git_dir, option_template, GIT_HASH_UNKNOWN, NULL,
>  		INIT_DB_QUIET);
>  
> -	if (real_git_dir)
> +	if (real_git_dir) {
> +		free((char *)git_dir);
>  		git_dir = real_git_dir;
> +	}
>  
>  	/*
>  	 * additional config can be injected with -c, make sure it's included

I had to wonder if the old git_dir can still be pointed at by junk_git_dir. Much earlier than this point there is this:

	if (real_git_dir) {
		if (real_dest_exists)
			junk_git_dir_flags |= REMOVE_DIR_KEEP_TOPLEVEL;
		junk_git_dir = real_git_dir;
	} else {
		if (dest_exists)
			junk_git_dir_flags |= REMOVE_DIR_KEEP_TOPLEVEL;
		junk_git_dir = git_dir;
	}
	if (safe_create_leading_directories_const(git_dir) < 0)
		die(_("could not create leading directories of '%s'"), git_dir);

Luckily, junk_git_dir gets git_dir only when !real_git_dir, so it is safe. real_git_dir can only be set via the --separate-git-dir command line option, so we are safe here.

Thanks.