[BUG] CRASH: ECPGprepared_statement() and ECPGdeallocate_all() when connection is NULL

Hi,

The ECPG application crashes with a segmentation fault when calling
specific deallocation or prepared statement functions without an
established database connection. This is caused by a missing NULL check on
the connection handle before attempting to access it.

The issue is reproducible on the MASTER branch and affects older versions
up to v13.

The issue can be reproduced by modifying existing test cases, such as
src/interfaces/ecpg/test/sql/execute.pgc or
src/interfaces/ecpg/test/sql/desc.pgc. The general method is to skip the EXEC
SQL CONNECT statement (or intentionally force the connection to fail).

To specifically isolate the crash in ECPGdeallocate_all() and prevent the
program from hitting the ECPGprepared_statement() crash first, modify the
desc.pgc test file by moving the EXEC SQL DEALLOCATE ALL statement to an
earlier point

*Seg fault in ECPGprepared_statement():*
[434574]: ECPGdebug: set to 1
[434574]: ECPGconnect: opening database ecpg1_regression on <DEFAULT> port
<DEFAULT>
[434574]: ECPGconnect: connection to server on socket "/tmp/.s.PGSQL.5444"
failed: FATAL: database "ecpg1_regression" does not exist
[434574]: ecpg_finish: connection main closed
[434574]: raising sqlcode -402 on line 24: could not connect to database
"ecpg1_regression" on line 24
SQL error: could not connect to database "ecpg1_regression" on line 24
[434574]: raising sqlcode -220 on line 25: connection "NULL" does not exist
on line 25
SQL error: connection "NULL" does not exist on line 25
[434574]: raising sqlcode -220 on line 26: connection "NULL" does not exist
on line 26
SQL error: connection "NULL" does not exist on line 26
[434574]: raising sqlcode -220 on line 29: connection "NULL" does not exist
on line 29
SQL error: connection "NULL" does not exist on line 29
[434574]: raising sqlcode -220 on line 32: connection "NULL" does not exist
on line 32
SQL error: connection "NULL" does not exist on line 32
[434574]: raising sqlcode -220 on line 35: connection "NULL" does not exist
on line 35
SQL error: connection "NULL" does not exist on line 35
Inserted 0 tuples via execute immediate
[434574]: raising sqlcode -220 on line 40: connection "NULL" does not exist
on line 40
SQL error: connection "NULL" does not exist on line 40
[434574]: raising sqlcode -220 on line 41: connection "NULL" does not exist
on line 41
SQL error: connection "NULL" does not exist on line 41
Inserted 0 tuples via prepared execute
[434574]: raising sqlcode -220 on line 45: connection "NULL" does not exist
on line 45
SQL error: connection "NULL" does not exist on line 45
[434574]: raising sqlcode -220 on line 49: connection "NULL" does not exist
on line 49
SQL error: connection "NULL" does not exist on line 49

Program received signal SIGSEGV, Segmentation fault.
0x0000fffff7f92654 in ecpg_find_prepared_statement (name=0xaaaaaaaa1aa8
"f", con=0x0, prev_=0x0) at prepare.c:277
277 for (this = con->prep_stmts, prev = NULL;
(gdb) bt
#0 0x0000fffff7f92654 in ecpg_find_prepared_statement (name=0xaaaaaaaa1aa8
"f", con=0x0, prev_=0x0) at prepare.c:277
#1 0x0000fffff7f92aa8 in ecpg_prepared (name=0xaaaaaaaa1aa8 "f", con=0x0)
at prepare.c:393
#2 0x0000fffff7f92afc in ECPGprepared_statement (connection_name=0x0,
name=0xaaaaaaaa1aa8 "f", lineno=53)
at prepare.c:404

#3 0x0000aaaaaaaa0f74 in main () at
/home/shrkc/work/postgres/inst/bin/execute.pgc:52

*Seg fault in ECPGdeallocate_all() :*

Program received signal SIGSEGV, Segmentation fault.
0x0000fffff7f92a2c in ecpg_deallocate_all_conn (lineno=25,
c=ECPG_COMPAT_PGSQL, con=0x0) at prepare.c:372
372 while (con->prep_stmts)
(gdb) bt
#0 0x0000fffff7f92a2c in ecpg_deallocate_all_conn (lineno=25,
c=ECPG_COMPAT_PGSQL, con=0x0) at prepare.c:372
#1 0x0000fffff7f92a78 in ECPGdeallocate_all (lineno=25, compat=0,
connection_name=0x0) at prepare.c:384
#2 0x0000aaaaaaaa0e60 in main () at
/home/shrkc/work/postgres/inst/bin/desc.pgc:25

Please find the proposed patch attached below for your review.

Thanks & Regards,

Shruthi K C

EnterpriseDB: http://www.enterprisedb.com