Re: [PATCH -next] libbpf: Add additional null-pointer checking in make_parent_dir

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Gaosheng Cui <cuigaosheng1@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>, Martin Lau <kafai@fb.com>,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	john fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	gongruiqi1@huawei.com, wangweiyang2@huawei.com
Subject: Re: [PATCH -next] libbpf: Add additional null-pointer checking in make_parent_dir
Date: Thu, 21 Apr 2022 09:55:08 -0700	[thread overview]
Message-ID: <CAEf4Bza3inoAHsS0w=nKXNgxyFqzPXJVyDHq03Foody6Vgp7=Q@mail.gmail.com> (raw)
In-Reply-To: <20220421130056.2510372-1-cuigaosheng1@huawei.com>

On Thu, Apr 21, 2022 at 6:01 AM Gaosheng Cui <cuigaosheng1@huawei.com> wrote:
>
> The make_parent_dir is called without null-pointer checking for path,
> such as bpf_link__pin. To ensure there is no null-pointer dereference
> in make_parent_dir, so make_parent_dir requires additional null-pointer
> checking for path.
>
> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
> ---
>  tools/lib/bpf/libbpf.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index b53e51884f9e..5786e6184bf5 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -7634,6 +7634,9 @@ static int make_parent_dir(const char *path)
>         char *dname, *dir;
>         int err = 0;
>
> +       if (path == NULL)
> +               return -EINVAL;
> +

API contract is that path shouldn't be NULL. Just like we don't check
link, obj, prog for NULL in every single API, I don't think we need to
do it here, unless I'm missing something?

>         dname = strdup(path);
>         if (dname == NULL)
>                 return -ENOMEM;
> --
> 2.25.1
>