Re: [PATCH v3 1/4] environment.c: fix potential segfault by get_git_common_dir()

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 18, 2017, 17:54 UTC
Message-ID: <xmqq8to24gif.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20170318100206.5980-2-pclouds@gmail.com>

Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:

Show 8 quoted lines

> setup_git_env() must be called before this function to initialize
> git_common_dir so that it returns a non NULL string. And it must return
> a non NULL string or segfault can happen because all callers expect so.
>
> Normally if somebody has called get_git_dir(), or set_git_dir() then
> setup_git_env() is already called. But if you do setup_git_directory()
> at top dir (which skips set_git_dir) and never call get_git_dir, you'll
> get NULL here.

Hmph, and the solution for the problem not being "so let's make sure get_git_dir() is called even when the command is started at the top directory" is because...?

> test-ref-store.c will hit this problem because it's very lightweight,
> just enough initialization to exercise refs code, and get_git_dir() will
> never be called until get_worktrees() is, which uses get_git_common_dir().
> ---

Missing sign-off.

Show 15 quoted lines

>  environment.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/environment.c b/environment.c
> index 42dc3106d2..2986ee7200 100644
> --- a/environment.c
> +++ b/environment.c
> @@ -214,6 +214,8 @@ const char *get_git_dir(void)
>  
>  const char *get_git_common_dir(void)
>  {
> +	if (!git_dir)
> +		setup_git_env();
>  	return git_common_dir;
>  }