Re: BUG #18974: Postgresql repeatable crash after pg_upgrade from 15 to 17.5 version in postgresql_fdw queries

On Wed, Jul 2, 2025 at 9:35 AM Maxim Boguk <maxim(dot)boguk(at)gmail(dot)com> wrote:

>
>
> On Wed, Jul 2, 2025 at 3:03 AM Maxim Boguk <maxim(dot)boguk(at)gmail(dot)com> wrote:
>
>>
>>
>> On Wed, Jul 2, 2025 at 1:09 AM PG Bug reporting form <
>> noreply(at)postgresql(dot)org> wrote:
>>
>>> The following bug has been logged on the website:
>>>
>>> Bug reference: 18974
>>> Logged by: Maxim Boguk
>>> Email address: maxim(dot)boguk(at)gmail(dot)com
>>> PostgreSQL version: 17.5
>>> Operating system: Ubuntu
>>> Description:
>>>
>>> Postgresql repeatable crash after pg_upgrade from 15 to 17.5 version in
>>> postgresql_fdw timeouted (via query_timeout) queries
>>> Backtrace data from core file:
>>> Core was generated by `postgres: 17/main: **.app **_data [local] SELECT
>>> '.
>>> Program terminated with signal SIGSEGV, Segmentation fault.
>>> #0 __strcmp_evex () at ../sysdeps/x86_64/multiarch/strcmp-evex.S:314
>>> warning: 314 ../sysdeps/x86_64/multiarch/strcmp-evex.S: No such file
>>> or
>>> directory
>>> (gdb) bt
>>> #0 __strcmp_evex () at ../sysdeps/x86_64/multiarch/strcmp-evex.S:314
>>> #1 0x0000780820fd2df7 in emitHostIdentityInfo (conn=0x5d89b19f6d80,
>>> host_addr=0x7ffd34c50c70 "10.100.103.4") at
>>>
>>
>> (gdb) print ((PGconn *)0x5d89b19f6d80)->connhost[0]
>> $14 = {type = CHT_HOST_NAME, host = 0x0, hostaddr = 0x5d89b19c53b0
>> "10.100.103.4", port = 0x5d89b19c5390 "6503", password = 0x0}
>> As a result displayed_host = conn
>> <https://doxygen.postgresql.org/streamutil_8c.html#af4516154f33e07be1eadff88fab71465>
>> ->connhost
>> <https://doxygen.postgresql.org/structpg__conn.html#af613581f3bb3ef9a64acf0346c3cd92b>
>> [conn
>> <https://doxygen.postgresql.org/streamutil_8c.html#af4516154f33e07be1eadff88fab71465>
>> ->whichhost
>> <https://doxygen.postgresql.org/structpg__conn.html#aef258b7f6a1d241b2fad5728aa08a1ef>
>> ].host
>> <https://doxygen.postgresql.org/structpg__conn__host.html#a112de1e777da00724075fe6f65aaf3be> =
>> 0x0
>> and crash in line strcmp(displayed_host, host_addr) != 0
>>
>> related FDW definition:
>> FDW options | ( dbname '****', hostaddr '10.100.103.4', port
>> '6503')
>>
>
>
> related part of backtrace:
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0 __strcmp_evex () at ../sysdeps/x86_64/multiarch/strcmp-evex.S:314
>
> (gdb) bt
> #0 __strcmp_evex () at ../sysdeps/x86_64/multiarch/strcmp-evex.S:314
> #1 0x0000780820fd2df7 in emitHostIdentityInfo (conn=0x5d89b19f6d80,
> host_addr=0x7ffd34c50c70 "10.100.103.4") at
> /usr/src/postgresql-17-17.5-1.pgdg24.04+1/build/../src/interfaces/libpq/fe-connect.c:2128
> #2 0x0000780820fd8a0f in PQconnectPoll (conn=conn(at)entry=0x5d89b19f6d80)
> at
> /usr/src/postgresql-17-17.5-1.pgdg24.04+1/build/../src/interfaces/libpq/fe-connect.c:3038
> #3 0x0000780820fda44d in pqConnectDBStart (conn=0x5d89b19f6d80) at
> /usr/src/postgresql-17-17.5-1.pgdg24.04+1/build/../src/interfaces/libpq/fe-connect.c:2446
> #4 0x0000780820fda4e2 in PQcancelStart (cancelConn=cancelConn(at)entry=0x5d89b19f6d80)
> at
> /usr/src/postgresql-17-17.5-1.pgdg24.04+1/build/../src/interfaces/libpq/fe-cancel.c:198
> #5 0x000078082102401d in libpqsrv_cancel (conn=conn(at)entry=0x5d89b1785870,
> endtime=endtime(at)entry=804720445571683) at
> /usr/src/postgresql-17-17.5-1.pgdg24.04+1/build/../src/include/libpq/libpq-be-fe-helpers.h:399
>
> in libpqsrv_cancel conn have:
> (gdb) print ((PGconn *)0x5d89b1785870)->connhost[0]
> $14 = {type = CHT_HOST_ADDRESS, host = 0x0, hostaddr = 0x5d89b16cde00
> "10.100.103.4", port = 0x5d89b16cddc0 "6503", password = 0x0}
>
> new connection in PQcancelStart already have wrong type:
> (gdb) print ((PGconn *)0x5d89b19f6d80)->connhost[0]
> $15 = {type = CHT_HOST_NAME, host = 0x0, hostaddr = 0x5d89b19c53b0
> "10.100.103.4", port = 0x5d89b19c5390 "6503", password = 0x0}
>

As I understand the problem in PQcancelCreate() - which completely ignores
the existence of type in connhost structure.
As a result new connections got type=0 which maps on the first possible
value of
typedef enum pg_conn_host_type
{
CHT_HOST_NAME,
CHT_HOST_ADDRESS,
CHT_UNIX_SOCKET
} pg_conn_host_type;

--
Maxim Boguk
Senior Postgresql DBA

Phone UA: +380 99 143 0000
Phone AU: +61 45 218 5678