Hi Günther

> Date: 2026-10-21 23:22:50+0200
> From: Günther Noack <gnoack3000@gmail.com>
>
> The ETOOMANYREFS error is detected in too_many_unix_fds() in
> net/unix/af_unix.c when the user's (not the processes') in-flight FDs
> exceed RLIMIT_NOFILE, and the process has neither CAP_SYS_RESOURCE nor
> CAP_SYS_ADMIN.  The error is raised when all of the following
> (simplified) conditions are true:
> 
> * user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)
> * !capable(CAP_SYS_RESOURCE)
> * !capable(CAP_SYS_ADMIN)
> 
> The check was introduced in linux.git 712f4aad406b (2016-01-11; "unix:
> properly account for FDs passed over unix sockets").
> 
> Fixes: dc4eea68b565 (2016-12-17; "unix.7: Document ETOOMANYREFS for SCM_RIGHTS send exceeding RLIMIT_NOFILE limit")
> Cc: Michael Kerrisk <mtk.manpages@gmail.com>
> Cc: Willy Tarreau <w@1wt.eu>
> Cc: Kuniyuki Iwashima <kuniyu@google.com>
> Assisted-by: LLM
> Signed-off-by: Günther Noack <gnoack3000@gmail.com>
> ---

Reviewed-by: Alejandro Colomar <alx@kernel.org>

> 
> Notes:
>     Double checked in code -- the condition under which this error is
>     returned was not fully spelled out.
> 
>  man/man7/unix.7 | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/man/man7/unix.7 b/man/man7/unix.7
> index 79198445c581..0d2ea8bda2ae 100644
> --- a/man/man7/unix.7
> +++ b/man/man7/unix.7
> @@ -785,10 +785,14 @@ when sending a file descriptor as ancillary data over

Would you mind having a look at CONTRIBUTING.d/git for improving the
hunk context?

    git-diff(1), gitattributes(5)
	To produce useful hunk contexts in manual pages, we need to hack
	git(1)'s idea of a function name, and also to tell git what is a
	manual page.

		$ git config --global diff.man.xfuncname '^\.S[SHsh] .*$';
		$ mkdir -p ~/.config/git/;
		$ echo '*.[0-9]* diff=man' >>~/.config/git/attributes;


Cheers,
Alex

>  a UNIX domain socket (see the description of
>  .BR SCM_RIGHTS ,
>  above).
> -It occurs if the number of "in-flight" file descriptors exceeds the
> +It occurs if the number of "in-flight" file descriptors
> +sent by processes of the caller's real user ID
> +exceeds the caller's
>  .B RLIMIT_NOFILE
> -resource limit and the caller does not have the
> +resource limit and the caller has neither the
>  .B CAP_SYS_RESOURCE
> +nor the
> +.B CAP_SYS_ADMIN
>  capability.
>  An in-flight file descriptor is one that has been sent using
>  .BR sendmsg (2)
> -- 
> 2.56.0
> 
> 

-- 
<https://www.alejandro-colomar.es>