[v3] linux ttyname and ttyname_r: do not return wrong results
Commit Message
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>
---
Changelog: 2016-11-08
- remove obsolete comment in ttyname_r.c
- move is_pty() to common header file and mark as static inline
Changelog: 2016-11-22
- remove unneeded sys/symacros.h header
Changelog: 2016-11-24
- add Changelog entry
---
ChangeLog | 8 ++++++++
sysdeps/unix/sysv/linux/ttyname.c | 16 ++++++++++++----
sysdeps/unix/sysv/linux/ttyname.h | 35 +++++++++++++++++++++++++++++++++++
sysdeps/unix/sysv/linux/ttyname_r.c | 17 +++++++++++++----
4 files changed, 68 insertions(+), 8 deletions(-)
create mode 100644 sysdeps/unix/sysv/linux/ttyname.h
Comments
On Thu, Nov 24, 2016 at 02:32:36AM +0100, Christian Brauner wrote:
> 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>
> ---
> Changelog: 2016-11-08
> - remove obsolete comment in ttyname_r.c
> - move is_pty() to common header file and mark as static inline
> Changelog: 2016-11-22
> - remove unneeded sys/symacros.h header
> Changelog: 2016-11-24
> - add Changelog entry
> ---
> ChangeLog | 8 ++++++++
> sysdeps/unix/sysv/linux/ttyname.c | 16 ++++++++++++----
> sysdeps/unix/sysv/linux/ttyname.h | 35 +++++++++++++++++++++++++++++++++++
> sysdeps/unix/sysv/linux/ttyname_r.c | 17 +++++++++++++----
> 4 files changed, 68 insertions(+), 8 deletions(-)
> create mode 100644 sysdeps/unix/sysv/linux/ttyname.h
>
> diff --git a/ChangeLog b/ChangeLog
> index b6fc831..c236992 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,3 +1,11 @@
> +2016-11-23 Christian Brauner <christian.brauner@ubuntu.com>
> +
> + * sysdeps/unix/sysv/linux/ttyname.c: do not return wrong results when
> + detecting tty devices residing in a different namespace
> + * sysdeps/unix/sysv/linux/ttyname_r.c: do not return wrong results when
> + detecting tty devices residing in a different namespace
> + * sysdeps/unix/sysv/linux/ttyname.h: New file
This doesn't quite follow the style guidelines. A properly formatted
ChangeLog for this change would look like this:
2016-11-24 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.
@@ -1,3 +1,11 @@
+2016-11-23 Christian Brauner <christian.brauner@ubuntu.com>
+
+ * sysdeps/unix/sysv/linux/ttyname.c: do not return wrong results when
+ detecting tty devices residing in a different namespace
+ * sysdeps/unix/sysv/linux/ttyname_r.c: do not return wrong results when
+ detecting tty devices residing in a different namespace
+ * sysdeps/unix/sysv/linux/ttyname.h: New file
+
2016-11-23 Joseph Myers <joseph@codesourcery.com>
[BZ #20859]
@@ -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))
new file mode 100644
@@ -0,0 +1,35 @@
+/* Copyright (C) 2016 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
+}
+
@@ -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. */