[BZ #1460]

	* time/asctime.c (asctime_internal): New function, derived from
	asctime_r.  Takes additional parameter which is the buffer length.
	Use snprintf instead sprintf, if it overflows, fail.
	(asctime_r): Call asctime_internal with 26 as buffer length.
	(asctime): Call asctime_internal with length of internal buffer.
	* time/Makefile (tests): Add bug-asctime_r.
	* time/bug-asctime_r.c: New file.

1 files changed, 32 insertions, 17 deletions

diff --git a/time/asctime.c b/time/asctime.c
index 8ac4aa7..db29dff 100644
--- a/time/asctime.c
+++ b/time/asctime.c
@@ -31,17 +31,9 @@ extern const struct locale_data _nl_C_LC_TIME attribute_hidden;
 static const char format[] = "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n";
 static char result[	         3+1+ 3+1+20+1+20+1+20+1+20+1+20+1 + 1];
 
-/* Returns a string of the form "Day Mon dd hh:mm:ss yyyy\n"
-   which is the representation of TP in that form.  */
-char *
-asctime (const struct tm *tp)
-{
-  return __asctime_r (tp, result);
-}
-libc_hidden_def (asctime)
 
-char *
-__asctime_r (const struct tm *tp, char *buf)
+static char *
+asctime_internal (const struct tm *tp, char *buf, size_t buflen)
 {
   if (tp == NULL)
     {
@@ -58,19 +50,42 @@ __asctime_r (const struct tm *tp, char *buf)
      a buffer size would be passed.  */
   if (__builtin_expect (tp->tm_year > INT_MAX - 1900, 0))
     {
+    eoverflow:
       __set_errno (EOVERFLOW);
       return NULL;
     }
 
-  if (sprintf (buf, format,
-	       (tp->tm_wday < 0 || tp->tm_wday >= 7 ?
-		"???" : ab_day_name (tp->tm_wday)),
-	       (tp->tm_mon < 0 || tp->tm_mon >= 12 ?
-		"???" : ab_month_name (tp->tm_mon)),
-	       tp->tm_mday, tp->tm_hour, tp->tm_min,
-	       tp->tm_sec, 1900 + tp->tm_year) < 0)
+  int n = snprintf (buf, buflen, format,
+		    (tp->tm_wday < 0 || tp->tm_wday >= 7 ?
+		     "???" : ab_day_name (tp->tm_wday)),
+		    (tp->tm_mon < 0 || tp->tm_mon >= 12 ?
+		     "???" : ab_month_name (tp->tm_mon)),
+		    tp->tm_mday, tp->tm_hour, tp->tm_min,
+		    tp->tm_sec, 1900 + tp->tm_year);
+  if (n < 0)
     return NULL;
+  if (n >= buflen)
+    goto eoverflow;
 
   return buf;
 }
+
+
+/* Like asctime, but write result to the user supplied buffer.  The
+   buffer is only guaranteed to be 26 bytes in length.  */
+char *
+__asctime_r (const struct tm *tp, char *buf)
+{
+  return asctime_internal (tp, buf, 26);
+}
 weak_alias (__asctime_r, asctime_r)
+
+
+/* Returns a string of the form "Day Mon dd hh:mm:ss yyyy\n"
+   which is the representation of TP in that form.  */
+char *
+asctime (const struct tm *tp)
+{
+  return asctime_internal (tp, result, sizeof (result));
+}
+libc_hidden_def (asctime)