Message-ID: <552FD6C9.8060605@schaufler-ca.com>
Date: Thu, 16 Apr 2015 08:35:37 -0700
From: Casey Schaufler <casey@schaufler-ca.com>
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To: Seung-Woo Kim <sw0312.kim@samsung.com>, james.l.morris@oracle.com,
        serge@hallyn.com, linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org
CC: sumit.semwal@linaro.org, linaro-mm-sig@lists.linaro.org,
        jy0922.shim@samsung.com, Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [RFC PATCH] Security: ignore private inode from security_file_receive
References: <1429191656-8866-1-git-send-email-sw0312.kim@samsung.com>
In-Reply-To: <1429191656-8866-1-git-send-email-sw0312.kim@samsung.com>
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On 4/16/2015 6:40 AM, Seung-Woo Kim wrote:
> The dma-buf fd from anon_inode can be shared across processes, but
> there is no way to set security permission for the fd. So this
> patch fix just to ignore private inode from security_file_receive.
>
> Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> ---
>
> If security like smack is enabled, the dmabuf fd can not be shared between
> processes via unix domain socket. I am not familiar with security, so I am
> not sure that this kind of patch can be acceptable.

If an IS_PRIVATE() check is appropriate, it should be in
smack_file_receive(), not security_file_receive(). Why are you
looking at file->f_path.dentry->d_inode? That's not used in the
Smack access check. You'd want file->f_inode if anything.

Naked-by: Casey Schaufler <casey@schaufler-ca.com>

>
> Is there other option to share dmabuf fd via socket with security check?
>
> Best Regards,
> - Seung-Woo Kim
>
> ---
>  security/security.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/security/security.c b/security/security.c
> index 730ac65..c57354c 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -810,6 +810,9 @@ int security_file_send_sigiotask(struct task_struct *tsk,
>  
>  int security_file_receive(struct file *file)
>  {
> +
> +	if (unlikely(IS_PRIVATE(file->f_path.dentry->d_inode)))
> +		return 0;
>  	return security_ops->file_receive(file);
>  }
>  

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