Other calls to cpio_safer_name_suffix seem to be safe.

* src/copyin.c (process_copy_in):  Make sure that file_hdr.c_name
has at least two bytes allocated.
* src/util.c (cpio_safer_name_suffix): Document that use of this
function requires to be careful.
---
 src/copyin.c | 2 ++
 src/util.c   | 5 ++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/copyin.c b/src/copyin.c
index cde911e..032d35f 100644
--- a/src/copyin.c
+++ b/src/copyin.c
@@ -1385,6 +1385,8 @@ process_copy_in ()
          break;
        }
 
+      if (file_hdr.c_namesize <= 1)
+        file_hdr.c_name = xrealloc(file_hdr.c_name, 2);
       cpio_safer_name_suffix (file_hdr.c_name, false, !no_abs_paths_flag,
                              false);
       
diff --git a/src/util.c b/src/util.c
index 6ff6032..2763ac1 100644
--- a/src/util.c
+++ b/src/util.c
@@ -1411,7 +1411,10 @@ set_file_times (int fd,
 }
 
 /* Do we have to ignore absolute paths, and if so, does the filename
-   have an absolute path?  */
+   have an absolute path?
+   Before calling this function make sure that the allocated NAME buffer has
+   capacity at least 2 bytes to allow us to store the "." string inside.  */
+
 void
 cpio_safer_name_suffix (char *name, bool link_target, bool absolute_names,
                        bool strip_leading_dots)
-- 
2.5.0