linux-kernel - Re: [v3.7 Regression] [SCSI] sd: Implement support for WRITE SAME

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Date:	Wed, 19 Dec 2012 21:45:26 +0100
From:	Milan Broz <mbroz@...hat.com>
To:	Mike Snitzer <snitzer@...hat.com>
CC:	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Joseph Salisbury <joseph.salisbury@...onical.com>,
	Kernel Team <kernel-team@...ts.ubuntu.com>,
	linux-kernel@...r.kernel.org, jgarzik@...hat.com,
	JBottomley@...allels.com
Subject: Re: [v3.7 Regression]  [SCSI] sd: Implement support for WRITE SAME

On 12/19/2012 08:58 PM, Mike Snitzer wrote:
> On Wed, Dec 19 2012 at 11:58am -0500,
> Martin K. Petersen <martin.petersen@...cle.com> wrote:
> 
>>>>>>> "Joseph" == Joseph Salisbury <joseph.salisbury@...onical.com> writes:
>>
>> Joseph> I captured the netconsole output from boot until I reproduced
>> Joseph> the bug. The RIP points to kcryptd_crypt_write_io_submit() in
>> Joseph> ~/drivers/md/dm-crypt.c.  The output can be seen at:
>>
>> I'm thinking that dm-crypt should probably set max_write_same_sectors to
>> 0. It doesn't really make much sense for a crypto driver to pass that
>> command through.

IMHO WRITE_SAME doesn't not make sense in encrypted storage. The same sectors
in plaintext are _not_ the same in ciphertext. NEVER.
(If so, you have a security problem.)

It must be disabled in dmcrypt explicitly then (max_write_same_sectors?).

Is it only dmcrypt, or encrypted fs are affected too?

Milan

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