Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20190530035310.GA9127@zhanggen-UX430UQ>
In-Reply-To: <20190530035310.GA9127@zhanggen-UX430UQ>
From:   William Roberts <bill.c.roberts@gmail.com>
Date:   Wed, 29 May 2019 21:39:50 -0700
Message-ID: <CAFftDdrX_=7KXfbvMDdCamj84nzYB+QCGXWArD3=zEkPZsQ1eQ@mail.gmail.com>
Subject: Re: [PATCH] hooks: fix a missing-check bug in selinux_sb_eat_lsm_opts()
To:     Gen Zhang <blackgod016574@gmail.com>
Cc:     Paul Moore <paul@paul-moore.com>, tony.luck@intel.com,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Eric Paris <eparis@parisplace.org>, selinux@vger.kernel.org,
        linux-kernel@vger.kernel.org, bpf@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, May 29, 2019 at 8:55 PM Gen Zhang <blackgod016574@gmail.com> wrote:
>
> In selinux_sb_eat_lsm_opts(), 'arg' is allocated by kmemdup_nul(). It
> returns NULL when fails. So 'arg' should be checked.
>
> Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> ---
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 3ec702c..5a9e959 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -2635,6 +2635,8 @@ static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts)
>                                                 *q++ = c;
>                                 }
>                                 arg = kmemdup_nul(arg, q - arg, GFP_KERNEL);
> +                               if (!arg)
> +                                       return 0;

The routine seems to return 0 on success, why would it return 0 on ENOMEM?

>                         }
>                         rc = selinux_add_opt(token, arg, mnt_opts);
>                         if (unlikely(rc)) {