Alejandro Colomar <alx@kernel.org> writes:

> Hi Alyssa,
>
> On Sat, Dec 13, 2025 at 06:58:53PM +0100, Alyssa Ross wrote:
>> I was surprised to discover than an O_PATH file descriptor was
>> insufficient.
>
> How did you discover it?  Could you please link to relevant information
> (or kernel sources)?

By trying it!

Presumably it's the fd_empty() check at the beginning of the syscall
implementation in nsproxy.c.

>> Since the mode of nsfs files is always 0444, tell
>> callers to always a file descriptor opened for reading.
>
> Missing 'use'?

Yes.  Feel free to add it.