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Date: Thu,  6 Apr 2017 00:32:17 +0200
From: Christian Brauner <>
Cc: Christian Brauner <>
Subject: [PATCH 0/1] linux ttyname{_r}: return ENODEV not ENOENT

Hi guys,

After a long struggle we've recently upstreamed a patch to glibc that handles
the case where a pts device might not be available even though the corresponding
file desciptor refers to a terminal. The classic example is obviously mount
namespaces in Linux although this can also be caused by overmounting or other
scenarios. While musl correctly detects whether the pts device a given file
descriptor refers to can be retrieved it returns ENOENT. We've recently
upstreamed a patch to glibc which uses ENODEV. This has been after a discussion
about what errno would be most in line with POSIX. Additionally we fixed a bunch
of programs to handle the ENODEV case. It would be good if musl would also set
ENODEV instead of ENOENT to enable programs to have uniform handle on this case
and to minimize the differences between the libcs.

The patch in question is:

	commit 15e9a4f378c8607c2ae1aa465436af4321db0e23
	Author: Christian Brauner <>
	Date:   Fri Jan 27 15:59:59 2017 +0100

	    linux ttyname and ttyname_r: do not return wrong results

	    If a link (say /proc/self/fd/0) pointing to a device, say /dev/pts/2, in a
	    parent mount namespace is passed to ttyname, and a /dev/pts/2 exists (in a
	    different devpts) in the current namespace, then it returns /dev/pts/2.
	    But /dev/pts/2 is NOT the current tty, it is a different file and device.

	    Detect this case and return ENODEV.  Userspace can choose to take this as a hint
	    that the fd points to a tty device but to act on the fd rather than the link.

	    Signed-off-by: Serge Hallyn <>
	    Signed-off-by: Christian Brauner <>

If possible, please Cc me on this since I'm not subscribed to the mailing list


Christian Brauner (1):
  linux ttyname{_r}: return ENODEV not ENOENT

 src/unistd/ttyname_r.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


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