More carefully validate xlog location string inputs

Now that we have validate_xlog_location, call it from the previously
existing functions taking xlog locatoins as a string input.

Suggested by Fujii Masao

src/backend/access/transam/xlogfuncs.c

@@ -30,6 +30,10 @@
 #include "utils/guc.h"
 #include "utils/timestamp.h"
 
+
+static void validate_xlog_location(char *str);
+
+
 /*
  * pg_start_backup: set up for taking an on-line backup dump
  *
@@ -289,6 +293,8 @@ pg_xlogfile_name_offset(PG_FUNCTION_ARGS)
 	 */
 	locationstr = text_to_cstring(location);
 
+	validate_xlog_location(locationstr);
+
 	if (sscanf(locationstr, "%X/%X", &uxlogid, &uxrecoff) != 2)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@@ -361,6 +367,8 @@ pg_xlogfile_name(PG_FUNCTION_ARGS)
 
 	locationstr = text_to_cstring(location);
 
+	validate_xlog_location(locationstr);
+
 	if (sscanf(locationstr, "%X/%X", &uxlogid, &uxrecoff) != 2)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),