linux-kernel - Re: [PATCH] hooks: fix a missing-check bug in selinux_sb_eat_lsm

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Date:   Wed, 29 May 2019 21:39:50 -0700
From:   William Roberts <bill.c.roberts@...il.com>
To:     Gen Zhang <blackgod016574@...il.com>
Cc:     Paul Moore <paul@...l-moore.com>, tony.luck@...el.com,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Eric Paris <eparis@...isplace.org>, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] hooks: fix a missing-check bug in selinux_sb_eat_lsm_opts()

On Wed, May 29, 2019 at 8:55 PM Gen Zhang <blackgod016574@...il.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@...il.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)) {