lid: avoid reading beyond end of buffer for a long name

* libidu/idfile.h (stzncpy): Define, from coreutils.
* src/lid.c (query_ambiguous_prefix): Avoid buffer overrun.
Using strncpy to copy a too-long name would result in a "name"
that is not NUL-terminated, yet that name would be treated as
a NUL-terminated string immediately afterwards, via report_func,
which attempts to print it.
* libidu/fnprint.c (root_name): Use stzncpy in place of strncpy.
* NEWS (Bug fixes): Mention the bug fix.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/lid.c b/src/lid.c
index cd307c0..8a31268 100644
--- a/src/lid.c
+++ b/src/lid.c
@@ -1042,7 +1042,7 @@ query_ambiguous_prefix (unsigned int limit, report_func_t report_func)
 	{
 	  if (consecutive && key_style != ks_token)
 	    {
-	      strncpy (&name[1], old, limit);
+	      stzncpy (&name[1], old, limit - 2);
 	      (*report_func) (name, bits_to_flinkv (bits_vec));
 	    }
 	  consecutive = 0;
@@ -1064,7 +1064,7 @@ query_ambiguous_prefix (unsigned int limit, report_func_t report_func)
     }
   if (consecutive && key_style != ks_token)
     {
-      strncpy (&name[1], new, limit);
+      stzncpy (&name[1], new, limit - 2);
       (*report_func) (name, bits_to_flinkv (bits_vec));
     }
   return count;