Re: dm-crypt: Fix parsing of extended IV arguments.

[Mike Snitzer <snitzer@redhat.com>]

On Wed, Jan 09 2019 at  5:57am -0500,
Milan Broz <gmazyland@gmail.com> wrote:

> The dm-crypt cipher specification in a mapping table is defined as
>   cipher[:keycount]-chainmode-ivmode[:ivopts] or with the new crypt API format
>   capi:cipher_api_spec-ivmode[:ivopts].
> 
> For ESSIV, the parameter includes hash specification, for example aes-cbc-essiv:sha256.
> 
> The implementation expected that additional IV option never includes another dash '-' character
> 
> Unfortunately, with SHA3, we have now names like sha3-256, so the mapping table parser fails:
> 
> dmsetup create test --table "0 8 crypt aes-cbc-essiv:sha3-256 9c1185a5c5e9fc54612808977ee8f5b9e 0 /dev/sdb 0"
>   or (new format)
> dmsetup create test --table "0 8 crypt capi:cbc(aes)-essiv:sha3-256 9c1185a5c5e9fc54612808977ee8f5b9e 0 /dev/sdb 0"
> 
>   device-mapper: crypt: Ignoring unexpected additional cipher options
>   device-mapper: table: 253:0: crypt: Error creating IV
>   device-mapper: ioctl: error adding target to table
> 
> This patch fixes the dm-crypt constructor to ignore additional dash in IV options and also removes
> bogus warning (that is ignored anyway).
> 
> [This patch should go into stable tree as well.]

Rather than this it'd be useful to just be more explicit, e.g.:

Fixes: XXXXXXXX ("commit subject")
Cc: stable@vger.kernel.org # > 4.x?

Once I know which commit exposed us to this problem I can take care of
getting this fix staged for 5.0-rcX inclussion.

Thanks,
Mike