Re: [PATCH] block: Add config option to not allow writing to mounted devices

Christoph Hellwig
2023-06-14T07:18:31Z

On Tue, Jun 13, 2023 at 08:09:14AM +0200, Dmitry Vyukov wrote:
> I don't question there are use cases for the flag, but there are use
> cases for the config as well.
>
> Some distros may want a guarantee that this does not happen as it
> compromises lockdown and kernel integrity (on par with unsigned module
> loading).
> For fuzzing systems it also may be hard to ensure fine-grained
> argument constraints, it's much easier and more reliable to prohibit
> it on config level.

I'm fine with a config option enforcing write blocking for any
BLK_OPEN_EXCL open. Maybe the way to it is to:

a) have an option to prevent any writes to exclusive openers, including
a run-time version to enable it
b) allow to also block writes without that option. And maybe an
opt-in to allow writes might be the better way than doing it
the other way around.