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

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Hi

There is a bug in the script - there is:
$VERITYSETUP create $DEV_NAME $DEV_PARAMS $VERIFY_PARAMS $2 >>$DEV_OUT 
2>&1 && \
	fail "activation"

There should be "||" instead of "&&", so that the function fail is 
executed on failure.

If I replace "&&" with "||", the script behaves as expected - it fails and 
writes this:
# check_root_hash  512 9de18652fe74edfb9b805aaed72ae2aa48f94333f1ba5c452ac33b1c39325174 $SALT 1 sha256 2
[root hash][verify][activate][remove]verify fails
FAILED
VERITY header information for verity-hash
UUID:                   613837c4-6ca8-4add-a2e9-c1acfd5c8e96
Hash type:              1
Data blocks:            16384
Data block size:        512
Hash block size:        512
Hash algorithm:         sha256
Salt:                   
e48da609055204e89ae53b655ca2216dd983cf3cb829f34f63a297d106d53e2d
Root hash:              
9de18652fe74edfb9b805aaed72ae2aa48f94333f1ba5c452ac33b1c39325174
Verification failed at position 3072.
Verification of data area failed.
exit

Mikulas


On Thu, 15 Aug 2013, Chaitra Bhat wrote:

> Hi Mikulas,
> 
> I have attached a simple script to demonstrate what I was trying to tell. It is based on the verify-compat-test script. Feel free to modify the script; the script is basically to get the idea across.
> 
> For the Successful Case
> #source script_test
> #check_root_hash  512 9de18652fe74edfb9b805aaed72ae2aa48f94333f1ba5c452ac33b1c39325174 $SALT 1 sha256 2
> 
> For the Failure Case
> #source script_test
> #check_root_hash  512 9de18652fe74edfb9b805aaed72ae2aa48f94333f1ba5c452ac33b1c39325174 $SALT 1 sha256 1
> 
> Regards,
> Chaitra
> ________________________________________
> From: Mikulas Patocka [mpatocka@xxxxxxxxxx]
> Sent: 15 August 2013 01:23
> To: Chaitra Bhat
> Cc: device-mapper development; Alasdair G Kergon
> Subject: RE:  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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