Date: Fri, 6 Nov 2026 14:00:47 +0100
From: Alejandro Colomar <alx+linux-man@kernel.org>
To: =?utf-8?Q?G=C3=BCnther?= Noack <gnoack3000@gmail.com>
Cc: Kuniyuki Iwashima <kuniyu@google.com>, linux-man@vger.kernel.org, 
	Michael Kerrisk <mtk.manpages@gmail.com>, Willy Tarreau <w@1wt.eu>, Alejandro Colomar <alx@kernel.org>
Subject: Re: [PATCH v2 1/8] man/man7/unix.7: ERRORS: ETOOMANYREFS: Fix the
 conditions
Message-ID: <au3PaAVf051LxmaT@devuan>
References: <20261103202211.13820-1-gnoack3000@gmail.com>
 <20261103202211.13820-2-gnoack3000@gmail.com>
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From: Alejandro Colomar <alx+linux-man@kernel.org>
To: =?utf-8?Q?G=C3=BCnther?= Noack <gnoack3000@gmail.com>
Cc: Kuniyuki Iwashima <kuniyu@google.com>, linux-man@vger.kernel.org, 
	Michael Kerrisk <mtk.manpages@gmail.com>, Willy Tarreau <w@1wt.eu>, Alejandro Colomar <alx@kernel.org>
Subject: Re: [PATCH v2 1/8] man/man7/unix.7: ERRORS: ETOOMANYREFS: Fix the
 conditions
Message-ID: <au3PaAVf051LxmaT@devuan>
References: <20261103202211.13820-1-gnoack3000@gmail.com>
 <20261103202211.13820-2-gnoack3000@gmail.com>
MIME-Version: 1.0
In-Reply-To: <20261103202211.13820-2-gnoack3000@gmail.com>

Hi G=C3=BCnther,

> Date: 2026-11-03 21:22:03+0100
> From: G=C3=BCnther 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:
>=20
> * user->unix_inflight > task_rlimit(p, RLIMIT_NOFILE)
> * !capable(CAP_SYS_RESOURCE)
> * !capable(CAP_SYS_ADMIN)
>=20
> The check was introduced in linux.git 712f4aad406b (2016-01-11; "unix:
> properly account for FDs passed over unix sockets").
>=20
> Fixes: dc4eea68b565 (2016-12-17; "unix.7: Document ETOOMANYREFS for SCM_R=
IGHTS 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
> Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
> Reviewed-by: Alejandro Colomar <alx@kernel.org>
> Signed-off-by: G=C3=BCnther Noack <gnoack3000@gmail.com>
> ---

I've applied this patch.  Thanks!


Cheers,
Alex

>=20
> Notes:
>     Double checked in code -- the condition under which this error is
>     returned was not fully spelled out.
>=20
>  man/man7/unix.7 | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>=20
> diff --git a/man/man7/unix.7 b/man/man7/unix.7
> index 2163a91514b9..94b9e82af3c0 100644
> --- a/man/man7/unix.7
> +++ b/man/man7/unix.7
> @@ -775,10 +775,14 @@ .SH ERRORS
>  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)
> --=20
> 2.56.0
>=20
>=20

--=20
<https://www.alejandro-colomar.es>

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