Re: [PATCH] Segfault in pool_do_auth() when failover races with a new connection

Hi Emonda,

> Last night one of CI builds detected a segmentation fault in pgpool
> (4.7.2). I've ran an analysis on the coredump with Claude and came to
> the conclusion that this can happen when trying to open a connection
> in the middle of a failover.
>
> Symptom / backtrace (resolved from the core dump):
> pool_do_auth (src/auth/pool_auth.c:349) <-- SIGSEGV, fault addr 0x0
> connect_backend (src/protocol/child.c:1099) (PG_TRY block)
> get_backend_connection (src/protocol/child.c:2109)
> do_child (src/protocol/child.c:233)
>
> The crashing statement is:
> protoMajor = MAIN_CONNECTION(cp)->sp->major; /* pool_auth.c:349 */
> i.e. cp->slots[MAIN_NODE_ID] is NULL. From the core, the pool had
> slots[0] == NULL while slots[1]/slots[2] were valid, and MAIN_NODE_ID == 0.
>
> pool_initialize_private_backend_status() snapshots
> private_backend_status[] and my_main_node_id non‑atomically w.r.t. the
> parent's failover, so a child can capture my_main_node_id == 0 while
> node 0 is already CON_DOWN. new_connection() then never creates
> slots[0], and pool_do_auth() dereferences the NULL main slot. (Same
> class as the NULL‑MAIN_CONNECTION case noted in
> pool_virtual_main_db_node_id().)
>
> Attached is a patch that fixes the issue.

Thanks for the patch. I will look into it.

Regards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp