secure file deletion/SECRM support for JFFS2 and UBIFS

[Chris Packham]

On 04/28/2016 09:55 AM, Richard Weinberger wrote:
> Am 27.04.2016 um 23:49 schrieb Chris Packham:
>> On 04/27/2016 07:06 PM, Richard Weinberger wrote:
>>> On Wed, Apr 27, 2016 at 9:05 AM, Richard Weinberger
>>> <richard.weinberger at gmail.com> wrote:
>>>>> Is that something people on this list would be interested in? I realize
>>>>> JFFS2 is kind of in a twilight phase but we're really not able to
>>>>> migrate some customers away from it.
>>>>
>>>> This is definitely a nice feature.
>>>> But please keep in mind that you can overwrite data on flash. :-)
>>>
>>> Should be read "can't", of course...
>>>
>>
>> You can't overwrite with arbitrary data. But for NOR flash at least you
>> _can_ overwrite with 0 (at least I think you can). In other words if the
>> erased state is 0xff you can write 0xaa you would not be able to write
>> 0x55 without erasing the block first but you would be able to write 0x00.
>>
>> I was hoping to avoid having to do an immediate erase but if I'm wrong
>> that's what we'd have to do.
>
> Well, UBIFS and JFFS2 work on generic MTD, so having a special hack for NOR
> is not really what we want.

Agreed. I was hoping there was a similar trick for NAND which I'm less 
familiar with. The fallback behavior of an immediate erase is still 
doable but it has more corner cases that we'd need to be weary of.