Re: [PATCH 4/4] SELinux: allow userspace to read policy back out of the kernel

[Casey Schaufler <casey@schaufler-ca.com>]

Eric Paris wrote:
> On Mon, 2010-06-14 at 10:48 -0400, Stephen Smalley wrote:
>   
>> On Fri, 2010-06-11 at 12:37 -0400, Eric Paris wrote:
>>     
>>> There is interest in being able to see what the actual policy is that was
>>> loaded into the kernel.  The patch creates a new selinuxfs file
>>> /selinux/policy which can be read by userspace.  The actual policy that is
>>> loaded into the kernel will be written back out to userspace.
>>>       
>> Why a new node vs a read op for /selinux/load?
>>     
>
> No reason why I couldn't.  Just 'load' seemed to imply a connotation
> which wasn't appropriate.  If you prefer I'll switch it when I do
> another version.
>   

If it makes any difference Smack /smack/load does read as well as write.
You have the opportunity to make 2 or 3 users less confused if you do
things consistently. After all, Smack uses load because SELinux does,
the name is actually arbitrary, and why do something differently when
it doesn't really matter?

> -Eric
>   
>>> Signed-off-by: Eric Paris <eparis@redhat.com>
>>> ---
>>>
>>>       
>>> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
>>> index 1de60ce..2e022db 100644
>>> --- a/security/selinux/ss/services.c
>>> +++ b/security/selinux/ss/services.c
>>> @@ -3126,3 +3125,27 @@ netlbl_sid_to_secattr_failure:
>>>  	return rc;
>>>  }
>>>  #endif /* CONFIG_NETLABEL */
>>> +
>>> +/**
>>> + * security_read_policy - read the policy.
>>> + * @data: binary policy data
>>> + * @len: length of data in bytes
>>> + *
>>> + */
>>> +int security_read_policy(void *data, ssize_t *len)
>>> +{
>>> +	int rc = 0;
>>> +	struct policy_file file = { data, *len }, *fp = &file;
>>> +
>>> +	if (!ss_initialized)
>>> +		return -EINVAL;
>>> +
>>> +	read_lock_irq(&policy_rwlock);
>>> +	rc = policydb_write(&policydb, fp);
>>> +	read_unlock_irq(&policy_rwlock);
>>> +
>>> +	*len = (unsigned long)fp->data - (unsigned long)data;
>>> +
>>> +	return rc;
>>> +
>>> +}
>>>       
>> Why _irq?
>>     
>
> Stolen from security_load_policy() and shouldn't have been.  Will fix.
>
>
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>   


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