[Bug libc/10784] New: expect fails when calling ttyname on a serial port

["jaredtsmith at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

With the file:  
glibc-2.9/sysdeps/unix/sysv/linux/ttyname.c

I found that it can get failures in getttyname it has the variable 
getttyname_name that is re-used where it allocates a big enough chunk of 
memory and then re-uses it the problem is that it doesn't re-copy dev into the 
variable if it changes so you can end up in a situation with expect where the 
tty changes from /dev/ttys0 --> /dev/pts/1 however the way the code is written 
it will append 1 into /dev/ttys0 since it doesn't copy in /dev/pts as it 
should.  This causes it to return null and crash in expect.


Here is the patch I created for the issue:

diff -ruN glibc-2.9/sysdeps/unix/sysv/linux/ttyname.c glibc-2.9-
fixed/sysdeps/unix/sysv/linux/ttyname.c
--- glibc-2.9/sysdeps/unix/sysv/linux/ttyname.c 2006-12-05 15:25:29.000000000 -
0600
+++ glibc-2.9-fixed/sysdeps/unix/sysv/linux/ttyname.c   2009-10-15 
10:12:20.000000000 -0500
@@ -79,7 +79,21 @@
                return NULL;
              }
            *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/';
-         }
+         }else{
+                 // Need to copy dev string into the buffer.  The
+                  // variable is a static so it carries the value between
+                  // calls and there are situations where the tty can change
+                  // for example when running expect on a serial line it will
+                  // switch from /dev/ttys0 --> /dev/pty/x without this fix
+                  // expect will fail on a serial line as it ends up turning
+                  // /dev/ttys0 --> /dev/ttysx which is not valid causing it
+                  // to return a null value and fail.
+                 memcpy(getttyname_name, dev, devlen);  //copy the string 
plus the null terminator
+                  // The memcpy call following this to copy in d->d_name 
expects a trailing "/" to
+                  // be appended without that it will be off by one
+                 getttyname_name[devlen-1]='/';         //append the 
trailing "/"
+                  getttyname_name[devlen]='\0';          //NULL terminate the 
string
+          }
        memcpy (&getttyname_name[devlen], d->d_name, dlen);
        if (__xstat64 (_STAT_VER, getttyname_name, &st) == 0
 #ifdef _STATBUF_ST_RDEV

-- 
           Summary: expect fails when calling ttyname on a serial port
           Product: glibc
           Version: 2.9
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: jaredtsmith at gmail dot com
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10784

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