[#MDEV-4752] Segfault during parsing of illegal query

Any user of a mariadb server with the ability to 'USE' some database is able to cause a segfault on the server during command parsing.

CREATE DATABASE segfault; -- not strictly necessary. any database will work.

USE segfault;

SELECT * FROM t5 JOIN (t1 JOIN t2 UNION SELECT * FROM t3 JOIN t4); -- None of these tables need exist.

The only thing a user needs to be able to trigger this segfault is the ability to 'USE' some database. They need no other permissions.

st_select_lex::nest_last_join (this=0x7fffbc006718, thd=<optimized out>)

    at /home/allight/mariadb-upstream-bzr/sql/sql_parse.cc:6703

6703	    table->join_list= embedded_list;

(gdb) i s

#0  st_select_lex::nest_last_join (this=0x7fffbc006718, thd=<optimized out>)

    at /home/allight/mariadb-upstream-bzr/sql/sql_parse.cc:6703

#1  0x0000000000673c2d in MYSQLparse (yythd=<optimized out>)

    at /home/allight/mariadb-upstream-bzr/sql/sql_yacc.yy:9940

#2  0x0000000000596219 in parse_sql (thd=0x20ed5e8, parser_state=0x7ffff7f062c0, creation_ctx=0x0)

    at /home/allight/mariadb-upstream-bzr/sql/sql_parse.cc:8115

#3  0x0000000000596461 in mysql_parse (parser_state=0x7ffff7f062c0, thd=0x20ed5e8, rawbuf=<optimized out>,

    length=<optimized out>) at /home/allight/mariadb-upstream-bzr/sql/sql_parse.cc:6127

#4  mysql_parse (thd=0x20ed5e8, rawbuf=<optimized out>, length=65, parser_state=0x7ffff7f062c0)

    at /home/allight/mariadb-upstream-bzr/sql/sql_parse.cc:6097

#5  0x0000000000597a97 in dispatch_command (command=COM_QUERY, thd=0x20ed5e8, packet=<optimized out>,

    packet_length=<optimized out>) at /home/allight/mariadb-upstream-bzr/sql/sql_parse.cc:1274

#6  0x0000000000642354 in do_handle_one_connection (thd_arg=<optimized out>)

    at /home/allight/mariadb-upstream-bzr/sql/sql_connect.cc:1267

#7  0x00000000006423e0 in handle_one_connection (arg=<optimized out>)

    at /home/allight/mariadb-upstream-bzr/sql/sql_connect.cc:1181

#8  0x00007ffff77a5e9a in start_thread (arg=0x7ffff7f07700) at pthread_create.c:308

#9  0x00007ffff6a99ccd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112

#10 0x0000000000000000 in ?? ()

logs for a test run are attached.
Status and configuration information are also attached, created by running:

./client/mysql -u root -S instance/stock/mysql.sock <<EOF > out 2>out.err

create database if not exists segfault;

use segfault;

show variables;

show status;

SELECT * FROM t5 JOIN (t1 JOIN t2 UNION SELECT * FROM t3 JOIN t4);

EOF

[MDEV-4752] Segfault during parsing of illegal query Created: 2013-07-04 Updated: 2013-07-05 Resolved: 2013-07-05
Status:	Closed
Project:	MariaDB Server
Component/s:	None
Affects Version/s:	10.0.3, 5.5.31
Fix Version/s:	10.0.4, 5.5.32