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Fix memory corruption/crash in ANALYZE. 

This fixes an embarrassing oversight I (Andres) made in 737a292b,
namely missing two place where liverows/deadrows were used when
converting those variables to pointers, leading to incrementing the
pointer, rather than the value.

It's not that actually that easy to trigger a crash: One needs tuples
deleted by the current transaction, followed by a tuple deleted in
another session, all in one page. Which is presumably why this hasn't
been noticed before.

Reported-By: Steve Singer
Author: Steve Singer
Discussion: https://postgr.es/m/c7988239-d42c-ddc4-41db-171b23b35e4f@ssinger.info
This commit is contained in:
Andres Freund 2019-06-18 15:51:04 -07:00
parent 8b21b416ed
commit 23224563d9
3 changed files with 27 additions and 2 deletions
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4
src/backend/access/heap/heapam_handler.c
View File

@ -1113,11 +1113,11 @@ heapam_scan_analyze_next_tuple(TableScanDesc scan, TransactionId OldestXmin,
* concurrent transaction never commits.
*/
if (TransactionIdIsCurrentTransactionId(HeapTupleHeaderGetUpdateXid(targtuple->t_data)))
deadrows += 1;
*deadrows += 1;
else
{
sample_it = true;
liverows += 1;
*liverows += 1;
}
break;

12
src/test/regress/expected/vacuum.out
View File

@ -71,6 +71,18 @@ ANALYZE vaccluster;
ERROR: ANALYZE cannot be executed from VACUUM or ANALYZE
CONTEXT: SQL function "do_analyze" statement 1
SQL function "wrap_do_analyze" statement 1
-- Test ANALYZE in transaction, where the transaction surrounding
-- analyze performed modifications. This tests for the bug at
-- https://postgr.es/m/c7988239-d42c-ddc4-41db-171b23b35e4f%40ssinger.info
-- (which hopefully is unlikely to be reintroduced), but also seems
-- independently worthwhile to cover.
INSERT INTO vactst SELECT generate_series(1, 300);
DELETE FROM vactst WHERE i % 7 = 0; -- delete a few rows outside
BEGIN;
INSERT INTO vactst SELECT generate_series(301, 400);
DELETE FROM vactst WHERE i % 5 <> 0; -- delete a few rows inside
ANALYZE vactst;
COMMIT;
VACUUM FULL pg_am;
VACUUM FULL pg_class;
VACUUM FULL pg_database;

13
src/test/regress/sql/vacuum.sql
View File

@ -54,6 +54,19 @@ CREATE INDEX ON vaccluster(wrap_do_analyze(i));
INSERT INTO vaccluster VALUES (1), (2);
ANALYZE vaccluster;
-- Test ANALYZE in transaction, where the transaction surrounding
-- analyze performed modifications. This tests for the bug at
-- https://postgr.es/m/c7988239-d42c-ddc4-41db-171b23b35e4f%40ssinger.info
-- (which hopefully is unlikely to be reintroduced), but also seems
-- independently worthwhile to cover.
INSERT INTO vactst SELECT generate_series(1, 300);
DELETE FROM vactst WHERE i % 7 = 0; -- delete a few rows outside
BEGIN;
INSERT INTO vactst SELECT generate_series(301, 400);
DELETE FROM vactst WHERE i % 5 <> 0; -- delete a few rows inside
ANALYZE vactst;
COMMIT;
VACUUM FULL pg_am;
VACUUM FULL pg_class;
VACUUM FULL pg_database;