On Fri, Feb 26, 2016 at 10:36:50PM +0100, Stanislav Brabec wrote:That and that using a loop device is one of the ways to expose partitions on a device the kernel doesn't normally expose them from. In general, I'm pretty certain the preferred method is to use DM based mappings, but those aren't always available, and I've had multiple cases where I had to use nested loop devices to get to a filesystem.
It should definitely report error whenever trying -oloop on top of
anything else than a file. Or at least a warning.
Well, even losetup should report a warning.
Keep in mind that with crypto in the game it just might be useful to have
loop-over-loop - it might be _not_ a no-op (hell, you might have two
layers of encryption - not the smartest thing to do, but if that's what
got dumped on your lap, you deal with what you've got). So such warnings
shouldn't be hard errors.