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

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Date:	Wed, 23 Feb 2011 21:18:51 +0100 (CET)
From:	Lukas Czerner <lczerner@...hat.com>
To:	Cristian Rodríguez <crrodriguez@...nsuse.org>
cc:	Lukas Czerner <lczerner@...hat.com>,
	Greg Freemyer <greg.freemyer@...il.com>,
	opensuse-factory <opensuse-factory@...nsuse.org>,
	ext4 <linux-ext4@...r.kernel.org>, linux-fsdevel@...r.kernel.org
Subject: Re: [opensuse-factory] /sbin/fstrim: /home: FITRIM ioctl failed:
 Operation not supported

On Wed, 23 Feb 2011, Cristian Rodríguez wrote:

> 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 ?
> --

This is really a question for dm-crypt/block layer guys.
Adding linux-fsdevel@...r.kernel.org into cc.

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