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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87qzsy5htz.fsf@alyssa.is>
Date: Sat, 13 Dec 2025 19:59:04 +0100
From: Alyssa Ross <hi@...ssa.is>
To: Alejandro Colomar <alx@...nel.org>
Cc: Christian Brauner <brauner@...nel.org>, Al Viro
 <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org,
 linux-man@...r.kernel.org
Subject: Re: [PATCH] man/man2/setns.2: clarify type of nsfs fd required

Alejandro Colomar <alx@...nel.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.

Download attachment "signature.asc" of type "application/pgp-signature" (228 bytes)