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From:   Ondrej Mosnacek <omosnace@redhat.com>
Date:   Thu, 30 May 2019 10:30:17 +0200
Message-ID: <CAFqZXNtX1R1VDFxm7Jco3BZ=pVnNiHU3-C=d8MhCVV1XSUQ8bw@mail.gmail.com>
Subject: Re: [PATCH] hooks: fix a missing-check bug in selinux_add_mnt_opt()
To:     Gen Zhang <blackgod016574@gmail.com>
Cc:     Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Eric Paris <eparis@parisplace.org>, ccross@android.com,
        selinux@vger.kernel.org,
        Linux kernel mailing list <linux-kernel@vger.kernel.org>,
        netdev@vger.kernel.org
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On Thu, May 30, 2019 at 10:06 AM Gen Zhang <blackgod016574@gmail.com> wrote:
> In selinux_add_mnt_opt(), 'val' is allcoted by kmemdup_nul(). It returns
> NULL when fails. So 'val' should be checked.
>
> Signed-off-by: Gen Zhang <blackgod016574@gmail.com>

Please add a Fixes tag here, too:

Fixes: 757cbe597fe8 ("LSM: new method: ->sb_add_mnt_opt()")

> ---
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 3ec702c..4797c63 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1052,8 +1052,11 @@ static int selinux_add_mnt_opt(const char *option, const char *val, int len,
>         if (token == Opt_error)
>                 return -EINVAL;
>
> -       if (token != Opt_seclabel)
> -               val = kmemdup_nul(val, len, GFP_KERNEL);
> +       if (token != Opt_seclabel) {
> +                       val = kmemdup_nul(val, len, GFP_KERNEL);
> +                       if (!val)
> +                               return -ENOMEM;

There is one extra tab character in the above three lines ^^^

> +       }
>         rc = selinux_add_opt(token, val, mnt_opts);
>         if (unlikely(rc)) {
>                 kfree(val);

Thanks,

--
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.