Check for NULL being passed in.

c/src/lib/libc/readdir.c

@@ -56,6 +56,9 @@ readdir(dirp)
 register DIR *dirp; {
   register struct dirent *dp;
   
+  if ( !dirp )
+    return NULL;
+
   for (;;) {
     if (dirp->dd_loc == 0) {
       dirp->dd_size = getdents (dirp->dd_fd,

c/src/lib/libc/rewinddir.c

@@ -24,6 +24,9 @@ void rewinddir(
 {
   off_t status;
 
+  if ( !dirp )
+    return;
+
   status = lseek( dirp->dd_fd, 0, SEEK_SET );
  
   if( status == -1 )

c/src/lib/libc/seekdir.c

@@ -25,12 +25,16 @@ void seekdir(
 {
   off_t status;
 
+  if ( !dirp )
+    return;
+
   status = lseek( dirp->dd_fd, loc, SEEK_SET );
 
   /*
    * This is not a nice way to error out, but we have no choice here.
    */
-  if( status == -1 ) 
+
+  if ( status == -1 ) 
     return;
 
   dirp->dd_loc = 0;

c/src/lib/libc/telldir.c

@@ -16,6 +16,7 @@
 #include <dirent.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <errno.h>
 
 #include "libio_.h"
 
@@ -26,8 +27,12 @@ long telldir(
 {
   rtems_libio_t  *iop;
 
+  if ( !dirp )
+    set_errno_and_return_minus_one( EBADF ); 
+
   /*
-   *  Get the file control block structure associated with the file descriptor
+   *  Get the file control block structure associated with the
+   *  file descriptor
    */
 
   iop = rtems_libio_iop( dirp->dd_fd );