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Re: [dm-devel] dm-verity: Verification fails but do not see Input/Output Error on read



On Tue, 13 Aug 2013, Chaitra Bhat wrote:

> Hi Mikulas,
> 
> I figured out what was happening - but I would need your help to explain 
> these behaviours please :)
> 
> Case I - Format the hash device, verify and create the dm-verity target. 
> Then modify data in the underlying data-device using dd. Read back the 
> data from the modified location from the verity-device.
> 
> Result: Verify fails but 'NO' I/O error reported when reading back from 
> the location using dd.

So, create a script that results in this scenario of not reporting I/O 
error and send it to us.

Mikulas

> Case II - Format the hash device, verify and create the dm-verity target 
> device. Remove the verity target, then modify the data in the 
> data-device using dd. Load the verity target and read-back the data from 
> the verity-device from the modified location.
> 
> Result: Verify fails and also get I/O error on reading that location 
> using dd.
> 
> My understanding was that the verity-device could be created and mounted 
> and then if the underlying data was corrupted somehow, then a read of 
> invalid data from that corrupted location will return -EIO.
> 
> Chaitra
> 
> PS: I was following the examples in the verity-compat-test script.


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