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[PATCH] linux ttyname and ttyname_r: do not return wrong results
- From: Christian Brauner <christian dot brauner at canonical dot com>
- To: libc-alpha at sourceware dot org, serge at hallyn dot com
- Cc: Christian Brauner <christian dot brauner at canonical dot com>
- Date: Tue, 8 Nov 2016 17:56:38 +0100
- Subject: [PATCH] linux ttyname and ttyname_r: do not return wrong results
- Authentication-results: sourceware.org; auth=none
- References: <20161108165638.21674-1-christian.brauner@canonical.com>
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@canonical.com>
---
Changelog: 2016-11-08
- remove obsolete comment in ttyname_r.c
- move is_pty() to common header file and mark as static inline
---
sysdeps/unix/sysv/linux/ttyname.c | 17 +++++++++++++----
sysdeps/unix/sysv/linux/ttyname.h | 35 +++++++++++++++++++++++++++++++++++
sysdeps/unix/sysv/linux/ttyname_r.c | 18 ++++++++++++++----
3 files changed, 62 insertions(+), 8 deletions(-)
create mode 100644 sysdeps/unix/sysv/linux/ttyname.h
diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c
index 7a001b4..dabed22 100644
--- a/sysdeps/unix/sysv/linux/ttyname.c
+++ b/sysdeps/unix/sysv/linux/ttyname.c
@@ -25,9 +25,12 @@
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
+#include <sys/sysmacros.h>
#include <_itoa.h>
+#include "ttyname.h"
+
#if 0
/* Is this used anywhere? It is not exported. */
char *__ttyname;
@@ -170,12 +173,18 @@ 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))
diff --git a/sysdeps/unix/sysv/linux/ttyname.h b/sysdeps/unix/sysv/linux/ttyname.h
new file mode 100644
index 0000000..19af6e6
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/ttyname.h
@@ -0,0 +1,35 @@
+/* Copyright (C) 2004-2016 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
+}
+
diff --git a/sysdeps/unix/sysv/linux/ttyname_r.c b/sysdeps/unix/sysv/linux/ttyname_r.c
index d15bc74..542114b 100644
--- a/sysdeps/unix/sysv/linux/ttyname_r.c
+++ b/sysdeps/unix/sysv/linux/ttyname_r.c
@@ -25,9 +25,12 @@
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
+#include <sys/sysmacros.h>
#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 +155,19 @@ __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. */
--
2.9.3