linux-kernel - Re: [RFC PATCH] Security: ignore private inode from security_file

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Date:	Fri, 17 Apr 2015 11:00:01 +0900
From:	Seung-Woo Kim <sw0312.kim@...sung.com>
To:	Stephen Smalley <sds@...ho.nsa.gov>
Cc:	james.l.morris@...cle.com, serge@...lyn.com,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, sumit.semwal@...aro.org,
	linaro-mm-sig@...ts.linaro.org, jy0922.shim@...sung.com,
	Seung-Woo Kim <sw0312.kim@...sung.com>
Subject: Re: [RFC PATCH] Security: ignore private inode from
 security_file_receive

Hello,

On 2015년 04월 16일 22:48, Stephen Smalley wrote:
> On 04/16/2015 09:40 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@...sung.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.
>>
>> 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);
>>  }
> 
> SELinux handles this internally; see its inode_has_perm() function.
> Doing it here would prevent any security module checking at all, even of
> the struct file, which SELinux does presently do (selinux_file_receive
> calls file_has_perm which applies the fd use check and then calls
> inode_has_perm on the inode).  Unless you are saying that the
> file->f_security field is also not being set correctly.

Thanks for the suggestion. I will try to do on smack side.

Best Regards,
- Seung-Woo Kim

> 
> 
> 

-- 
Seung-Woo Kim
Samsung Software R&D Center
--

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