Re: [PATCH 06/10] security: fix documentation for the path_chmod hook

Stephen Smalley
2019-02-07T14:33:13Z

On 2/7/19 9:09 AM, Edwin Zimmerman wrote:
> On Thursday, February 07, 2019 8:50 AM Al Viro wrote:
>> On Thu, Feb 07, 2019 at 03:44:54PM +0300, Denis Efremov wrote:
>>> The path_chmod hook was changed in the commit
>>> "switch security_path_chmod() to struct path *" (cdcf116d44e7).
>>> The argument @mnt was removed from the hook, @dentry was changed
>>> to @path. This patch updates the documentation accordingly.
>>>
>>> Signed-off-by: Denis Efremov <efremov@ispras.ru>
>>> ---
>>> include/linux/lsm_hooks.h | 3 +--
>>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
>>> index cb93972257be..5d6428d0027b 100644
>>> --- a/include/linux/lsm_hooks.h
>>> +++ b/include/linux/lsm_hooks.h
>>> @@ -304,8 +304,7 @@
>>> * Return 0 if permission is granted.
>>> * @path_chmod:
>>> * Check for permission to change DAC's permission of a file or directory.
>>> - * @dentry contains the dentry structure.
>>> - * @mnt contains the vfsmnt structure.
>>> + * @path contains the path structure.
>>
>> May I politely inquire about the value of these comments? How much information
>> is provided by refering to an argument as "the dentry structure" or "the path
>> structure", especially when there's nothing immediately above that would introduce
>> either. "Type of 'dentry' argument is somehow related to struct dentry,
>> try and guess what the value might be - we don't care, we just need every
>> argument commented"?
>>
>> Who needs that crap in the first place?
>
> The comments fill a valuable place to folks like me who are new to the linux security modules.
> In my spare time, I'm writing a new LSM specifically geared for parental controls uses, and the
> comments in lsm_hooks.h have helped me out more than once. Perhaps the comments could
> be inproved by changing them to something like this:
> "@[arg] contains the [type] structure, defined in linux/[?].h"

I don't think so. The point is not what type of structure but what
object is being passed and why is it relevant to the hook, e.g.

+ @path contains the path structure for the file whose permissions are
being modified

or similar.