[1/2] linux ttyname: return link if appropriate
Commit Message
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 | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
Comments
On 18 Apr 2016 19:53, Serge Hallyn wrote:
> + strcpy (ttyname_buf, procname);
> + return ttyname_buf;
at this point you could just write:
return strcpy (ttyname_buf, procname);
-mike
Quoting Mike Frysinger (vapier@gentoo.org):
> On 18 Apr 2016 19:53, Serge Hallyn wrote:
> > + strcpy (ttyname_buf, procname);
> > + return ttyname_buf;
>
> at this point you could just write:
> return strcpy (ttyname_buf, procname);
Yup.
I can send another patch (squashed), but I'm sort of waiting
for Florian's answer about security concerns.
@@ -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 +183,22 @@ 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)
+ {
+ strcpy (ttyname_buf, procname);
+ return ttyname_buf;
+ }
}
if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))