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Subject: Re: New mode DM-Verity error handling
To:     Milan Broz <gmazyland@gmail.com>,
        Mike Snitzer <snitzer@redhat.com>,
        Sami Tolvanen <samitolvanen@google.com>
Cc:     dm-devel@redhat.com, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, agk@redhat.com, corbet@lwn.net
From:   JeongHyeon Lee <jhs2.lee@samsung.com>
Message-ID: <579f4147-1825-1825-84be-2088ea670a64@samsung.com>
Date:   Tue, 23 Jun 2020 17:08:02 +0900
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Dear Milan Broz.


Thank you for answer my query.

I asked you again because i was confused.


Yes, I also looked at the document and get a lot of information or 
studies related to dm-verity.

https://gitlab.com/cryptsetup/cryptsetup/-/wikis/DMVerity


Thank you : D

JeongHyeon Lee


On 23/06/2020 16:28, Milan Broz wrote:
> On 23/06/2020 01:53, JeongHyeon Lee wrote:
>> For what reason isn't panic better?
> I did not say panic is better, I said that while we have restart already in mainline dm-verity code,
> panic() is almost the same, so I see no problem in merging this patch.
>
> Stopping system this way could create more damage if it is not configured properly,
> but I think it is quite common to stop the system as fast as possible if data system integrity
> is violated...
>
>> If when i suggested new patch, i will send you a patch that increased
>> minor version.
> I think Mike can fold-in version increase, if the patch is accepted.
>
> But please include these version changes with every new feature.
>
> Actually I am tracking it here for dm-verity as part of veritysetup userspace documentation:
>    https://gitlab.com/cryptsetup/cryptsetup/-/wikis/DMVerity
>
> Thanks,
> Milan
>
>> On 22/06/2020 16:58, Milan Broz wrote:
>>> On 18/06/2020 19:09, Mike Snitzer wrote:
>>>> On Thu, Jun 18 2020 at 12:50pm -0400,
>>>> Sami Tolvanen <samitolvanen@google.com> wrote:
>>>>
>>>>> On Thu, Jun 18, 2020 at 11:44:45AM -0400, Mike Snitzer wrote:
>>>>>> I do not accept that panicing the system because of verity failure is
>>>>>> reasonable.
>>>>>>
>>>>>> In fact, even rebooting (via DM_VERITY_MODE_RESTART) looks very wrong.
>>>>>>
>>>>>> The device should be put in a failed state and left for admin recovery.
>>>>> That's exactly how the restart mode works on some Android devices. The
>>>>> bootloader sees the verification error and puts the device in recovery
>>>>> mode. Using the restart mode on systems without firmware support won't
>>>>> make sense, obviously.
>>>> OK, so I need further justification from Samsung why they are asking for
>>>> this panic mode.
>>> I think when we have reboot already, panic is not much better :-)
>>>
>>> Just please note that dm-verity is used not only in Android world (with own tooling)
>>> but in normal Linux distributions, and I need to modify userspace (veritysetup) to support
>>> and recognize this flag.
>>>
>>> Please *always* increase minor dm-verity target version when adding a new feature
>>> - we can then provide some better hint if it is not supported.
>>>
>>> Thanks,
>>> Milan
>>>
>>>
>