Re: [PATCH] man/man2/setns.2: clarify type of nsfs fd required

From: Alyssa Ross

Date: Sat Dec 13 2025 - 13:59:13 EST


Alejandro Colomar <alx@xxxxxxxxxx> 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.

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