diff mbox

linux ttyname and ttyname_r: return link if appropriate

Message ID 20160420021012.GA19449@ubuntumail
State New
Headers show

Commit Message

Serge E. Hallyn April 20, 2016, 2:10 a.m. UTC 
The current ttyname does the wrong thing in two cases:

1. If the passed-in link (say /proc/self/fd/0) points to a
device, say /dev/pts/2, in a parent mount namespace, 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.

2. If the passed-in link (say /proc/self/fd/0) points to
a device, say /dev/pts/2, in a parent mount namespace, and
/dev/pts/2 does not exist in the current namespace, it
returns success but an empty name.  As far as I can tell,
there is no reason for it to not return /proc/self/fd/0.
http://pubs.opengroup.org/onlinepubs/009695399/functions/ttyname.html
does not say anything about not returning a link.
---
 sysdeps/unix/sysv/linux/ttyname.c   | 20 ++++++++++++++++++++
 sysdeps/unix/sysv/linux/ttyname_r.c | 22 ++++++++++++++++++++++
 2 files changed, 42 insertions(+)

Comments

Mike Frysinger April 20, 2016, 2:28 a.m. UTC | #1 
On 20 Apr 2016 02:10, Serge Hallyn wrote:
> --- a/sysdeps/unix/sysv/linux/ttyname.c
> +++ b/sysdeps/unix/sysv/linux/ttyname.c
>
> +   linux/Documentation/devices.txt */

should be a period at the end followed by two spaces

> +  int m = major (sb->st_rdev);

you'll need to include sys/sysmacros.h in this file since you're using
major now.

> +      /* If the link doesn't exist, then it points to a device in another
> +	 namespace.  If it is a UNIX98 pty, then return the /proc/self
> +	 fd, as it points to a name unreachable in our namespace */

should be "namespace.  */" at the end ;)

> --- a/sysdeps/unix/sysv/linux/ttyname_r.c
> +++ b/sysdeps/unix/sysv/linux/ttyname_r.c

same comments here
-mike
diff mbox

Patch

diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c
index 7a001b4..932140a 100644
--- a/sysdeps/unix/sysv/linux/ttyname.c
+++ b/sysdeps/unix/sysv/linux/ttyname.c
@@ -33,6 +33,19 @@ 
 char *__ttyname;
 #endif
 
+/* Return true if this is a UNIX98 pty device, as defined in
+   linux/Documentation/devices.txt */
+static 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
+}
+
 static char *getttyname (const char *dev, dev_t mydev,
 			 ino64_t myino, int save, int *dostat)
      internal_function;
@@ -170,12 +183,19 @@  ttyname (int fd)
 #ifdef _STATBUF_ST_RDEV
 	  && S_ISCHR (st1.st_mode)
 	  && st1.st_rdev == st.st_rdev
+	  && st1.st_dev == st.st_dev
 #else
 	  && st1.st_ino == st.st_ino
 	  && st1.st_dev == st.st_dev
 #endif
 	  )
 	return ttyname_buf;
+
+      /* If the link doesn't exist, then it points to a device in another
+	 namespace.  If it is a UNIX98 pty, then return the /proc/self
+	 fd, as it points to a name unreachable in our namespace */
+      if (is_pty (&st) && strlen (procname) < buflen - 1)
+	return strcpy (ttyname_buf, procname);
     }
 
   if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))
diff --git a/sysdeps/unix/sysv/linux/ttyname_r.c b/sysdeps/unix/sysv/linux/ttyname_r.c
index d15bc74..e3d0c8b 100644
--- a/sysdeps/unix/sysv/linux/ttyname_r.c
+++ b/sysdeps/unix/sysv/linux/ttyname_r.c
@@ -32,6 +32,19 @@  static int getttyname_r (char *buf, size_t buflen,
 			 dev_t mydev, ino64_t myino, int save,
 			 int *dostat) internal_function;
 
+/* Return true if this is a UNIX98 pty device, as defined in
+   linux/Documentation/devices.txt */
+static 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
+}
+
 static int
 internal_function attribute_compat_text_section
 getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
@@ -158,6 +171,15 @@  __ttyname_r (int fd, char *buf, size_t buflen)
 #endif
 	  )
 	return 0;
+
+      /* If the link doesn't exist, then it points to a device in another
+	 namespace.  If it is a UNIX98 pty, then return the /proc/self
+	 fd, as it points to a name unreachable in our namespace */
+      if (is_pty (&st) && strlen (procname) < buflen - 1)
+	{
+	  strcpy (buf, procname);
+	  return 0;
+	}
     }
 
   /* Prepare the result buffer.  */