Bug#42634: % character in query can cause mysqld signal 11 segfault

The problem is that a unfiltered user query was being passed as
the format string parameter of sql_print_warning which later
performs printf-like formatting, leading to crashes if the user
query contains formatting instructions (ie: %s). Also, it was
using THD::query as the source of the user query, but this
variable is not meaningful in some situations -- in a delayed
insert, it points to the table name.

The solution is to pass the user query as a parameter for the
format string and use the function parameter query_arg as the
source of the user query.

mysql-test/suite/binlog/r/binlog_unsafe.result

@@ -220,3 +220,10 @@ Warning	1592	Statement is not safe to log in statement format.
 Warning	1592	Statement is not safe to log in statement format.
 DROP PROCEDURE p1;
 DROP TABLE t1;
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1 (a VARCHAR(100), b VARCHAR(100));
+INSERT INTO t1 VALUES ('a','b');
+UPDATE t1 SET b = '%s%s%s%s%s%s%s%s%s%s%s%s%s%s' WHERE a = 'a' LIMIT 1;
+Warnings:
+Warning	1592	Statement is not safe to log in statement format.
+DROP TABLE t1;

mysql-test/suite/binlog/t/binlog_unsafe.test

@@ -257,3 +257,17 @@ delimiter ;|
 CALL p1();
 DROP PROCEDURE p1;
 DROP TABLE t1;
+
+#
+# Bug#42634: % character in query can cause mysqld signal 11 segfault
+#
+
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+
+CREATE TABLE t1 (a VARCHAR(100), b VARCHAR(100));
+INSERT INTO t1 VALUES ('a','b');
+UPDATE t1 SET b = '%s%s%s%s%s%s%s%s%s%s%s%s%s%s' WHERE a = 'a' LIMIT 1;
+DROP TABLE t1;
+

sql/sql_class.cc

@@ -3660,16 +3660,14 @@ int THD::binlog_query(THD::enum_binlog_query_type qtype, char const *query_arg,
   if (lex->is_stmt_unsafe() &&
       variables.binlog_format == BINLOG_FORMAT_STMT)
   {
-    DBUG_ASSERT(this->query != NULL);
     push_warning(this, MYSQL_ERROR::WARN_LEVEL_WARN,
                  ER_BINLOG_UNSAFE_STATEMENT,
                  ER(ER_BINLOG_UNSAFE_STATEMENT));
     if (!(binlog_flags & BINLOG_FLAG_UNSAFE_STMT_PRINTED))
     {
-      char warn_buf[MYSQL_ERRMSG_SIZE];
-      my_snprintf(warn_buf, MYSQL_ERRMSG_SIZE, "%s Statement: %s",
-                  ER(ER_BINLOG_UNSAFE_STATEMENT), this->query);
-      sql_print_warning(warn_buf);
+      sql_print_warning("%s Statement: %.*s",
+                        ER(ER_BINLOG_UNSAFE_STATEMENT),
+                        MYSQL_ERRMSG_SIZE, query_arg);
       binlog_flags|= BINLOG_FLAG_UNSAFE_STMT_PRINTED;
     }
   }