linux-kernel - Re: [PATCH] Add file permission mode helpers

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Date:	Wed, 3 Aug 2016 11:53:06 +0200
From:	Marcel Holtmann <marcel@...tmann.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pavel Machek <pavel@....cz>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Baole Ni <baolex.ni@...el.com>,
	Russell King - ARM Linux <linux@...linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	chuansheng.liu@...el.com
Subject: Re: [PATCH] Add file permission mode helpers

Hi Greg,

>> An added advantage would be that during review it would stick out like a sore 
>> thumb if anyone used a 'weird' permission variant.
>> 
>> For example, if you saw these lines in a driver patch:
>> 
>> +	__ATTR(l1, 0444, driver_show_l4, NULL);
>> +		__ATTR(l3, 0446, driver_show_l4, NULL);
>> +			__ATTR(l2, 04444, driver_show_l4, NULL);
>> +		__ATTR(l4, 0444, driver_show_l4, NULL);
>> 
>> ... would you notice it at a glance that it contains two security holes?
> 
> I've tried to deal with that in the past with the __ATTR_RW() and
> __ATTR_RO() and __ATTR_WO() macros that more should be using.  I swept
> the tree a few years ago to try to fix up most of them, but I know I
> didn't catch them all, and more files have been added since then.

I said in another response that maybe module_param_rw and module_param_ro will make some sense. Not sure if they are easier to read or not. I mean for each usage, we could look at the tree and see what values are actually used. My bet is that for module_param only a few ones are used. I have the feeling it is 0444 or 0644 and nothing else. Maybe some outlaws with 0400 and 0600 that don't even need to be that secretive.

Regards

Marcel