linux-kernel - Re: [PATCH v4 20/19] LSM: Correct file blob free empty blob check

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Message-ID: <CAGXu5jLrvuhGonjCxUxMXi+HeEb8yWina=31OCvEqOeBBu1pkw@mail.gmail.com>
Date:   Mon, 1 Oct 2018 13:29:25 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     LSM <linux-security-module@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        SE Linux <selinux@...ho.nsa.gov>,
        LKLM <linux-kernel@...r.kernel.org>,
        John Johansen <john.johansen@...onical.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Salvatore Mesoraca <s.mesoraca16@...il.com>
Subject: Re: [PATCH v4 20/19] LSM: Correct file blob free empty blob check

On Wed, Sep 26, 2018 at 2:57 PM, Casey Schaufler <casey@...aufler-ca.com> wrote:
> Instead of checking if the kmem_cache for file blobs
> has been initialized check if the blob is NULL. This
> allows non-blob using modules to do other kinds of
> clean up in the security_file_free hooks.
>
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

This looks like it should get folded into "LSM: Infrastructure
management of the file security".

-Kees


> ---
>  security/security.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/security/security.c b/security/security.c
> index e7c8506041f1..76f7dc49b63c 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1202,14 +1202,13 @@ void security_file_free(struct file *file)
>  {
>         void *blob;
>
> -       if (!lsm_file_cache)
> -               return;
> -
>         call_void_hook(file_free_security, file);
>
>         blob = file->f_security;
> -       file->f_security = NULL;
> -       kmem_cache_free(lsm_file_cache, blob);
> +       if (blob) {
> +               file->f_security = NULL;
> +               kmem_cache_free(lsm_file_cache, blob);
> +       }
>  }
>
>  int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> --
> 2.17.1
>
>



-- 
Kees Cook
Pixel Security