BUG #19382: Server crash at __nss_database_lookup

The following bug has been logged on the website:

Bug reference: 19382
Logged by: Yuxiao Guo
Email address: dllggyx(at)outlook(dot)com
PostgreSQL version: 17.7
Operating system: Ubuntu 20.04 x86-64, docker image postgres:17.7
Description:

Hi, I found a crash in PostgreSQL. Here are the details:

PoC:
DROP FUNCTION IF EXISTS bar();
DROP TYPE IF EXISTS foo CASCADE;
CREATE TYPE foo AS (a INT, b INT);
CREATE FUNCTION bar() RETURNS RECORD AS $$
DECLARE
r foo := ROW(123, power(2, 30));
BEGIN
ALTER TYPE foo ALTER ATTRIBUTE b TYPE TEXT;
RETURN r;
END;
$$ LANGUAGE plpgsql;
SELECT bar();

DROP TYPE IF EXISTS foo CASCADE;
CREATE TYPE foo AS (a INT, b INT);
BEGIN;
DECLARE c CURSOR FOR SELECT (i, power(2, 30))::foo FROM
generate_series(1,10) i;
FETCH c;
ALTER TYPE foo ALTER ATTRIBUTE b TYPE TEXT;
FETCH c;
COMMIT;

Stacktrace:
#0 0x7182a7813b38 (__nss_database_lookup+0x284b8)
#1 0x91c9e5 (textout+0x85)
#2 0x94cbd3 (OutputFunctionCall+0x33)
#3 0x8db524 (record_out+0x244)
#4 0x94cbd3 (OutputFunctionCall+0x33)
#5 0x49fafc (printtup+0x2bc)
#6 0x7fc888 (RunFromStore+0xa8)
#7 0x7fbeb5 (PortalRunSelect+0x75)
#8 0x7fbbbe (PortalRun+0x16e)
#9 0x7fadd5 (exec_simple_query+0x585)
#10 0x7f8929 (PostgresMain+0x949)
#11 0x7f45bf (BackendMain+0x3f)
#12 0x75df24 (postmaster_child_launch+0x94)
#13 0x762101 (ServerLoop+0x1d61)
#14 0x75faab (PostmasterMain+0xd8b)
#15 0x6a3349 (main+0x2f9)
#16 0x7182a76ac083 (__libc_start_main+0xf3)
#17 0x49006e (_start+0x2e)