From b9ea609855b838369cddb33e4045ac91603dd726 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Wed, 15 Nov 2023 23:44:56 +0100 Subject: [PATCH v1 1/1] Fix resource leak when a FDW's ForeignAsyncRequest function fails If an error is thrown after calling CreateWaitEventSet(), the memory of a WaitEventSet is free'd as it's allocated in the short-lived memory context, but the file descriptor (on epoll- or kqueue-based systems) or handles (on Windows) that it contains are leaked. Use PG_TRY-FINALLY to ensure it gets freed. In the passing, fix misleading comment on what the 'nevents' argument to WaitEventSetWait means. The added test doesn't check for leaking resources, so it passed even before this commit. But at least it covers the code path. Report by Alexander Lakhin, analysis and suggestion for the fix by Tom Lane. Discussion: https://www.postgresql.org/message-id/17828-122da8cba23236be@postgresql.org Discussion: https://www.postgresql.org/message-id/472235.1678387869@sss.pgh.pa.us --- .../postgres_fdw/expected/postgres_fdw.out | 7 ++ contrib/postgres_fdw/sql/postgres_fdw.sql | 6 ++ src/backend/executor/nodeAppend.c | 66 +++++++++++-------- 3 files changed, 50 insertions(+), 29 deletions(-) diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index 64bcc66b8d..22cae37a1e 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -10809,6 +10809,13 @@ SELECT * FROM result_tbl ORDER BY a; (2 rows) DELETE FROM result_tbl; +-- Test error handling, if accessing one of the foreign partitions errors out +CREATE FOREIGN TABLE async_p_broken PARTITION OF async_pt FOR VALUES FROM (10000) TO (10001) + SERVER loopback OPTIONS (table_name 'non_existent_table'); +SELECT * FROM async_pt; +ERROR: relation "public.non_existent_table" does not exist +CONTEXT: remote SQL command: SELECT a, b, c FROM public.non_existent_table +DROP FOREIGN TABLE async_p_broken; -- Check case where multiple partitions use the same connection CREATE TABLE base_tbl3 (a int, b int, c text); CREATE FOREIGN TABLE async_p3 PARTITION OF async_pt FOR VALUES FROM (3000) TO (4000) diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index 2d14eeadb5..075da4ff86 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -3607,6 +3607,12 @@ INSERT INTO result_tbl SELECT a, b, 'AAA' || c FROM async_pt WHERE b === 505; SELECT * FROM result_tbl ORDER BY a; DELETE FROM result_tbl; +-- Test error handling, if accessing one of the foreign partitions errors out +CREATE FOREIGN TABLE async_p_broken PARTITION OF async_pt FOR VALUES FROM (10000) TO (10001) + SERVER loopback OPTIONS (table_name 'non_existent_table'); +SELECT * FROM async_pt; +DROP FOREIGN TABLE async_p_broken; + -- Check case where multiple partitions use the same connection CREATE TABLE base_tbl3 (a int, b int, c text); CREATE FOREIGN TABLE async_p3 PARTITION OF async_pt FOR VALUES FROM (3000) TO (4000) diff --git a/src/backend/executor/nodeAppend.c b/src/backend/executor/nodeAppend.c index 609df6b9e6..99818d3ebc 100644 --- a/src/backend/executor/nodeAppend.c +++ b/src/backend/executor/nodeAppend.c @@ -1025,43 +1025,51 @@ ExecAppendAsyncEventWait(AppendState *node) /* We should never be called when there are no valid async subplans. */ Assert(node->as_nasyncremain > 0); + Assert(node->as_eventset == NULL); node->as_eventset = CreateWaitEventSet(CurrentMemoryContext, nevents); - AddWaitEventToSet(node->as_eventset, WL_EXIT_ON_PM_DEATH, PGINVALID_SOCKET, - NULL, NULL); - - /* Give each waiting subplan a chance to add an event. */ - i = -1; - while ((i = bms_next_member(node->as_asyncplans, i)) >= 0) + PG_TRY(); { - AsyncRequest *areq = node->as_asyncrequests[i]; + AddWaitEventToSet(node->as_eventset, WL_EXIT_ON_PM_DEATH, PGINVALID_SOCKET, + NULL, NULL); - if (areq->callback_pending) - ExecAsyncConfigureWait(areq); - } + /* Give each waiting subplan a chance to add an event. */ + i = -1; + while ((i = bms_next_member(node->as_asyncplans, i)) >= 0) + { + AsyncRequest *areq = node->as_asyncrequests[i]; - /* - * No need for further processing if there are no configured events other - * than the postmaster death event. - */ - if (GetNumRegisteredWaitEvents(node->as_eventset) == 1) + if (areq->callback_pending) + ExecAsyncConfigureWait(areq); + } + + /* + * No need for further processing if there are no configured events + * other than the postmaster death event. + */ + if (GetNumRegisteredWaitEvents(node->as_eventset) == 1) + { + FreeWaitEventSet(node->as_eventset); + node->as_eventset = NULL; + return; + } + + /* Return at most EVENT_BUFFER_SIZE events in one call. */ + if (nevents > EVENT_BUFFER_SIZE) + nevents = EVENT_BUFFER_SIZE; + + /* + * If the timeout is -1, wait until at least one event occurs. If the + * timeout is 0, poll for events, but do not wait at all. + */ + noccurred = WaitEventSetWait(node->as_eventset, timeout, occurred_event, + nevents, WAIT_EVENT_APPEND_READY); + } + PG_FINALLY(); { FreeWaitEventSet(node->as_eventset); node->as_eventset = NULL; - return; } - - /* We wait on at most EVENT_BUFFER_SIZE events. */ - if (nevents > EVENT_BUFFER_SIZE) - nevents = EVENT_BUFFER_SIZE; - - /* - * If the timeout is -1, wait until at least one event occurs. If the - * timeout is 0, poll for events, but do not wait at all. - */ - noccurred = WaitEventSetWait(node->as_eventset, timeout, occurred_event, - nevents, WAIT_EVENT_APPEND_READY); - FreeWaitEventSet(node->as_eventset); - node->as_eventset = NULL; + PG_END_TRY(); if (noccurred == 0) return; -- 2.39.2