linux-ext4 - Re: [opensuse-factory] /sbin/fstrim: /home: FITRIM ioctl failed: Operation not supported

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Date:	Wed, 23 Feb 2011 16:12:06 -0300
From:	Cristian Rodríguez <crrodriguez@...nsuse.org>
To:	Lukas Czerner <lczerner@...hat.com>
CC:	Greg Freemyer <greg.freemyer@...il.com>,
	opensuse-factory <opensuse-factory@...nsuse.org>,
	ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [opensuse-factory] /sbin/fstrim: /home: FITRIM ioctl failed:
 Operation not supported

El 23/02/11 07:28, Lukas Czerner escribió:
> On Tue, 22 Feb 2011, Greg Freemyer wrote:
> 
>> On Tue, Feb 22, 2011 at 6:09 PM, Cristian Rodríguez
>> <crrodriguez@...nsuse.org> wrote:
>>>  Hi:
>>>
>>>  I get the error message in $Subject if I try to use /sbin/fstrim on all
>>>  my filesystems BUT /boot which is the only one which is not encrypted.
>>>
>>>  How am I supposed to "trim" dm-crypt/LUKS volumes on an SSD device ?
>>>
>>> Thanks.

Lukas, thanks for your answer.

> No NO NO! Big no to trimming encrypted filesystems! When you are
> discarding blocks, the subsequent read from those blocks are usually "well
> defined" and hence you are giving away useful information for attacker
> trying to decrypt your filesystem. 

I understand that there might be security issues, but so far, for this
scenario the only kind of attacker from which I need to protect my
desktop is from low-funded regular thieves that may break into my home
office, unlikely that will get pass the volume password prompt ;-)


> Now, there might be some way around this to allow trimming encrypted
> volumes without serious security issue, but this is rather question for
> dm-crypt guys.

Maybe making work the "discard" mount option ?
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