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linux ttyname and ttyname_r: do not return wrong results

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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>
This commit is contained in:
Christian Brauner 2017-01-27 15:59:59 +01:00 committed by Dmitry V. Levin
parent 345118d7f5
commit 15e9a4f378
4 changed files with 71 additions and 8 deletions
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12
ChangeLog
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@ -1,3 +1,15 @@
2017-03-19 Christian Brauner <christian.brauner@ubuntu.com>
* sysdeps/unix/sysv/linux/ttyname.h: New file.
* sysdeps/unix/sysv/linux/ttyname.c: Include "ttyname.h".
(ttyname) [!_STATBUF_ST_RDEV]: Make code unconditional.
Call is_pty when the link does not exist or does not match, fail
with ENODEV when it returns true.
* sysdeps/unix/sysv/linux/ttyname_r.c: Include "ttyname.h".
(__ttyname_r) [!_STATBUF_ST_RDEV]: Make code unconditional.
Call is_pty when the link does not exist or does not match, fail
with ENODEV when it returns true.
2017-03-18 Joseph Myers <joseph@codesourcery.com>
[BZ #16437]

16
sysdeps/unix/sysv/linux/ttyname.c
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@ -28,6 +28,8 @@
#include <_itoa.h>
#include "ttyname.h"
#if 0
/* Is this used anywhere? It is not exported. */
char *__ttyname;
@ -170,12 +172,18 @@ ttyname (int fd)
#ifdef _STATBUF_ST_RDEV
&& S_ISCHR (st1.st_mode)
&& st1.st_rdev == st.st_rdev
#else
&& st1.st_ino == st.st_ino
&& st1.st_dev == st.st_dev
#endif
)
&& st1.st_ino == st.st_ino
&& st1.st_dev == st.st_dev)
return ttyname_buf;
/* If the link doesn't exist, then it points to a device in another
namespace. */
if (is_pty (&st))
{
__set_errno (ENODEV);
return NULL;
}
}
if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))

34
sysdeps/unix/sysv/linux/ttyname.h Normal file
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@ -0,0 +1,34 @@
/* 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
}

17
sysdeps/unix/sysv/linux/ttyname_r.c
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@ -28,6 +28,8 @@
#include <_itoa.h>
#include "ttyname.h"
static int getttyname_r (char *buf, size_t buflen,
dev_t mydev, ino64_t myino, int save,
int *dostat) internal_function;
@ -152,12 +154,19 @@ __ttyname_r (int fd, char *buf, size_t buflen)
#ifdef _STATBUF_ST_RDEV
&& S_ISCHR (st1.st_mode)
&& st1.st_rdev == st.st_rdev
#else
&& st1.st_ino == st.st_ino
&& st1.st_dev == st.st_dev
#endif
)
&& st1.st_ino == st.st_ino
&& st1.st_dev == st.st_dev)
return 0;
/* If the link doesn't exist, then it points to a device in another
* namespace.
*/
if (is_pty (&st))
{
__set_errno (ENODEV);
return ENODEV;
}
}
/* Prepare the result buffer. */