Re: [PATCH 0/2] Shared flags

[Pavel Shilovsky <piastry@etersoft.ru>]

Christoph Hellwig wrote:
> On Tue, Nov 11, 2008 at 10:09:40AM +0000, Jamie Lokier wrote:
>   
>> Christoph Hellwig wrote:
>>     
>>> On Mon, Nov 10, 2008 at 04:58:17PM +0300, Pavel Shilovsky wrote:
>>>       
>>>> #define O_DENYREAD      004000000 /* Do not permit read access */
>>>> #define O_DENYWRITE     010000000 /* Do not permit write access */
>>>> #define O_DENYDELETE  020000000 /* Do not permit delete or rename operations*/
>>>>         
>>>  (2) you also need to enforce these semantics in the VFS for local
>>>      filesystems
>>>
>>> Now if (2) doesn't cause too much overhead I would say it's fine, if not
>>> I would rather avoid it.
>>>       
>> On the face of it, they look like they have similar denial-of-service
>> potential as mandatory locks.  For example, a root process cleaning
>> out /tmp gets stuck because a user process has O_DENYDELETE set.
>>     
>
> Oh, that's the part I forgot to mention in the previous mail, all of
> these option of course can only be root only, everything else would
> be - as you say - a complete security nightmare.
>
>   
We suggest to switch on this flags with special options during mounting. 
By default, it'll be switch off.
This solution deletes possibility of such situations, like in example.

Pavel Shilovsky.