Re: [RFC] block: relax permission for Persistent Reservations ioctl

[Christoph Hellwig]

On Fri, Jun 09, 2023 at 06:21:22PM +0800, Jingbo Xu wrote:
> When the shared storage is accessed from containers [1], it's not
> recommended to grant CAP_SYS_ADMIN to containers for access to
> Persistent Reservations in risk of container escape.
> 
> Remove the extra CAP_SYS_ADMIN permission constraint for Persistent
> Reservations ioctl which shall do no harm [2].

I think we still to check that if CAP_SYS_ADMIN is not present,
the file descriptors needs to be open for write, and we're not called
on a partition (the latter should probbaly be always checked,
as a reservation for a partitions doesn't make sense).

But in general I think relaxing this is a good idea, we just need to
be very careful.  Looking at the discussion of unprivileged nvme
command passthrough might be a good start.