Bug#20894 Reproducible MySQL client segmentation fault

 - Add two null bytes in  "buff" variable allowing us to call
   get_arg two times also for strings longer than sizeof(buff) 

client/mysql.cc

@@ -2934,7 +2934,11 @@ com_connect(String *buffer, char *line)
   bzero(buff, sizeof(buff));
   if (buffer)
   {
-    strmake(buff, line, sizeof(buff) - 1);
+    /*
+      Two null bytes are needed in the end of buff to allow
+      get_arg to find end of string the second time it's called.
+    */
+    strmake(buff, line, sizeof(buff)-2);
     tmp= get_arg(buff, 0);
     if (tmp && *tmp)
     {

mysql-test/r/mysql.result

@@ -162,4 +162,21 @@ select count(*) from t17583;
 count(*)
 1280
 drop table t17583;
+Test connect without db- or host-name => reconnect
+Test connect with dbname only => new dbname, old hostname
+ERROR 1064 (42000) at line 1: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'connecttest' at line 1
+Test connect with _invalid_ dbname only => new invalid dbname, old hostname
+ERROR 1049 (42000) at line 1: Unknown database 'invalid'
+ERROR 1049 (42000) at line 1: Unknown database 'invalid'
+Test connect with dbname + hostname
+Test connect with dbname + _invalid_ hostname
+ERROR 2005 (HY000) at line 1: Unknown MySQL server host 'invalid_hostname' (errno)
+ERROR 2005 (HY000) at line 1: Unknown MySQL server host 'invalid_hostname' (errno)
+The commands reported in the bug report
+ERROR 2005 (HY000) at line 1: Unknown MySQL server host 'cyril has found a bug :)XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' (errno)
+ERROR 2005 (HY000) at line 1: Unknown MySQL server host 'cyril has found a bug :)XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' (errno)
+Too long dbname
+ERROR 1049 (42000) at line 1: Unknown database 'test_really_long_dbnameXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
+Too long hostname
+ERROR 2005 (HY000) at line 1: Unknown MySQL server host 'cyrils_superlonghostnameXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' (errno)
 End of 5.0 tests

mysql-test/t/mysql.test

@@ -170,4 +170,57 @@ select count(*) from t17583;
 --exec echo "select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; select count(*) from t17583; " |$MYSQL test >&-
 drop table t17583;
 
+#
+# Bug#20984: Reproducible MySQL client segmentation fault
+#  + additional tests for the "com_connect" function in mysql
+#
+#
+--echo Test connect without db- or host-name => reconnect
+--exec $MYSQL test -e "\r" 2>&1
+--exec $MYSQL test -e "connect" 2>&1
+
+--echo Test connect with dbname only => new dbname, old hostname
+--exec $MYSQL test -e "\r test" 2>&1
+--exec $MYSQL test -e "connect test" 2>&1
+--exec $MYSQL test -e "\rtest" 2>&1
+--error 1
+--exec $MYSQL test -e "connecttest" 2>&1
+
+--echo Test connect with _invalid_ dbname only => new invalid dbname, old hostname
+--error 1
+--exec $MYSQL test -e "\r invalid" 2>&1
+--error 1
+--exec $MYSQL test -e "connect invalid" 2>&1
+
+--echo Test connect with dbname + hostname
+--exec $MYSQL test -e "\r test localhost" 2>&1
+--exec $MYSQL test -e "connect test localhost" 2>&1
+
+--echo Test connect with dbname + _invalid_ hostname
+# Mask the errno of the error message
+--replace_regex /\([0-9]*\)/(errno)/
+--error 1
+--exec $MYSQL test -e "\r test invalid_hostname" 2>&1
+--replace_regex /\([0-9]*\)/(errno)/
+--error 1
+--exec $MYSQL test -e "connect test invalid_hostname" 2>&1
+
+--echo The commands reported in the bug report
+--replace_regex /\([0-9]*\)/(errno)/
+--error 1
+--exec $MYSQL test -e "\r\r\n\r\n cyril\ has\ found\ a\ bug\ :)XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX" 2>&1
+
+--replace_regex /\([0-9]*\)/(errno)/
+--error 1
+--exec echo '\r\r\n\r\n cyril\ has\ found\ a\ bug\ :)XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' | $MYSQL 2>&1
+
+--echo Too long dbname
+--error 1
+--exec echo '\r test_really_long_dbnameXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX localhost' | $MYSQL 2>&1
+
+--echo Too long hostname
+--replace_regex /\([0-9]*\)/(errno)/
+--error 1
+--exec echo '\r  test cyrils_superlonghostnameXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX' | $MYSQL 2>&1
+
 --echo End of 5.0 tests