block dangerous passthrough operation

[Kanchan Joshi]

On Wed, Nov 16, 2022 at 04:44:15PM +0100, Christoph Hellwig wrote:
>On Wed, Nov 16, 2022 at 07:13:22PM +0530, Kanchan Joshi wrote:
>> I see, good to know. I am still missing something.
>> This series is on top of nvme-6.2, since nvme_cmd_allowed did not exist
>> earlier.
>> In that case having this series or not having - gives the same effect,
>> no?
>
>Yes, no change due to the series introducing nvme_cmd_allowed.
>It is just a convenient place to put the checks.

Got it now. The series is about restricting root/admin itself from doing
certain things.
If we end up going this route, putting a new helper seems clearer to me.
Something like this: 

if (capable(CAP_SYS_ADMIN)) {
	return admin_only_checks();
}
/* regular user checks as before */


But if there are people using the upstream driver for testing
nvme-hardware, restricting may not go well. Stuff like creating SQ/CQ
in early stages of new SSD/controller development may just be
the thing they want to test.