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Check CREATE_REPLICATION_SLOT response shape in libpqwalreceiver

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Previously, libpqrcv_create_slot() checked only that
CREATE_REPLICATION_SLOT returned PGRES_TUPLES_OK before reading
values from the first row. If the server unexpectedly returned an
invalid result, such as zero rows, PQgetvalue() could return NULL,
leading to a crash while parsing the LSN.

Other replication commands, such as IDENTIFY_SYSTEM, already validate
the response shape before accessing result values, but
CREATE_REPLICATION_SLOT did not.

Fix this by verifying that CREATE_REPLICATION_SLOT response contains
exactly one row with four fields, and report a protocol violation otherwise.

Backpatch to all supported versions.

Bug: #19547
Reported-by: Yuelin Wang <1217816127@qq.com>
Author: Kenny Chen <kennychen851228@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/19547-f7986f668f71e788@postgresql.org
Discussion: https://postgr.es/m/CAPXstDtW2iqe+DJAOTQTX+rRziJp2UhZSo1+HRj1COAtbu+nKw@mail.gmail.com
Backpatch-through: 14
This commit is contained in:
Fujii Masao
2026-07-16 13:38:34 +09:00
parent 39a9c4079c
commit 1423a6efd0
1 changed files with 8 additions and 0 deletions
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8
src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
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@@ -1147,6 +1147,14 @@ libpqrcv_create_slot(WalReceiverConn *conn, const char *slotname,
slotname, pchomp(PQerrorMessage(conn->streamConn)))));
}
/* CREATE_REPLICATION_SLOT returns a single row with four columns */
if (PQnfields(res) != 4 || PQntuples(res) != 1)
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("invalid response from primary server"),
errdetail("Could not create replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields.",
slotname, PQntuples(res), PQnfields(res), 1, 4)));
if (lsn)
*lsn = DatumGetLSN(DirectFunctionCall1Coll(pg_lsn_in, InvalidOid,
CStringGetDatum(PQgetvalue(res, 0, 1))));