glibc/sysdeps/unix/sysv/linux/ttyname.h
Christian Brauner 15e9a4f378 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 <serge@hallyn.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2017-03-19 17:36:13 +00:00

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C

/* Copyright (C) 2016-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <http://www.gnu.org/licenses/>. */
#include <unistd.h>
#include <sys/sysmacros.h>
#include <sys/types.h>
#include <sys/stat.h>
/* Return true if this is a UNIX98 pty device, as defined in
linux/Documentation/devices.txt. */
static inline int
is_pty (struct stat64 *sb)
{
#ifdef _STATBUF_ST_RDEV
int m = major (sb->st_rdev);
return (136 <= m && m <= 143);
#else
return false;
#endif
}