[dm-devel] dm-crypt: Reject sector_size feature if device length is not aligned to it

[Milan Broz]

On 10/03/2017 10:08 PM, Mikulas Patocka wrote:
> 
> It would be interesting to know, why Milan wants the table load to fail.

I mentioned this on IRC:
the only situation I care about in load is that size (dm-table length) is unaligned to optional sector_size.
create fails in this case, load should imho fail as well. 
...
if we say that dmsetup table output is always directly usable (as a mapping table),
then why should there be an exception for dmsetup table --inactive? (now it can print apparently invalid mapping)

Anyway, I am ok if it fails in resume - but do not keep the device suspended after the fail!

> It could be possible to check the validity of the alignment in the 
> cryptsetup tool and not attempt to load invalid tables at all. Is there 
> any reason, why we need to detect the misalignment in the kernel?

Cryptsetup already rejects such a mapping before even calling dm-ioctl.

But anyone can use dmsetup tool to do that. I just think that incompatible
sector vs. device size should be rejected in target constructor.
(IOW my former patch for dm-crypt that rejects only this exact situation without
doing more device-related tests like your generalized patch in table_load.)

Milan