[dm-crypt] inconsistency in opening multiple mappers on the same device

.. ink .. mhogomchungu at gmail.com
Fri Jun 1 00:12:02 CEST 2012


I read the announcement of 1.4.3 and decided to do a simple test on
opening multiple mappers on the same device and this is what i found
out:

test using cryptsetup 1.4.3

[root at mtz ink]# echo -n xxx | cryptsetup create zzz xxx
[root at mtz ink]# echo -n xxx | cryptsetup create zzz xxx
Device zzz already exists.
[root at mtz ink]# echo -n xxx | cryptsetup create yyy xxx

[root at mtz ink]# ls -l /dev/mapper/
total 0
crw------- 1 root root 10, 236 May 29 14:46 control
lrwxrwxrwx 1 root root       7 May 31 18:01 yyy -> ../dm-1
lrwxrwxrwx 1 root root       7 May 31 18:01 zzz -> ../dm-0

[root at mtz ink]# zuluCrypt-cli -P -d /dev/mapper/zzz
/home/ink/xxx
[root at mtz ink]# zuluCrypt-cli -P -d /dev/mapper/yyy
/home/ink/xxx
[root at mtz ink]#

It looks like by default, cryptsetup does not allow opening more than
one mapper on the same device bu it only checks the mapper name, not
the device behind the mapper and hence it allows opening of multiple
mappers on the same device as long as they use a different mapper
name.

The same behavior is there in luks based volume

Also,shouldnt  the error say mapper name since the check is on the
mapper,not the device behind the mapper.


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