dm-crypt accepts '+' in the key

[Mikulas Patocka]

Hi

dm-crypt uses the function kstrtou8 to decode the encryption key. kstrtou8 
calls kstrtoull and kstrtoull skips the first character if it is '+'.

Consequently, it is possible to load keys with '+' in it. For example, 
this is possible:

dmsetup create cr --table "0 131072 crypt aes-cbc-essiv:sha256 +0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0+0 0 /dev/debian/tmptest 0"

Should this be fixed in dm-crypt or in kstrtou8? A fix in kstrtou8 could 
be more appropriate, but we don't know how many other kernel parts depend 
on this "skip plus" behavior...

Mikulas