From 48eb6a3c895dac239f7e04fc3d62c09a17c1fc4a Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Mon, 8 Jun 2020 13:57:24 +1200 Subject: [PATCH] Fix locking bugs that could corrupt pg_control. The redo routines for XLOG_CHECKPOINT_{ONLINE,SHUTDOWN} must acquire ControlFileLock before modifying ControlFile->checkPointCopy, or the checkpointer could write out a control file with a bad checksum. Likewise, XLogReportParameters() must acquire ControlFileLock before modifying ControlFile and calling UpdateControlFile(). Back-patch to all supported releases. Author: Nathan Bossart Author: Fujii Masao Reviewed-by: Fujii Masao Reviewed-by: Michael Paquier Reviewed-by: Thomas Munro Discussion: https://postgr.es/m/70BF24D6-DC51-443F-B55A-95735803842A%40amazon.com --- src/backend/access/transam/xlog.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 28f19f1c786..bceef897d6e 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -9680,6 +9680,8 @@ XLogReportParameters(void) XLogFlush(recptr); } + LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); + ControlFile->MaxConnections = MaxConnections; ControlFile->max_worker_processes = max_worker_processes; ControlFile->max_prepared_xacts = max_prepared_xacts; @@ -9688,6 +9690,8 @@ XLogReportParameters(void) ControlFile->wal_log_hints = wal_log_hints; ControlFile->track_commit_timestamp = track_commit_timestamp; UpdateControlFile(); + + LWLockRelease(ControlFileLock); } } @@ -9912,8 +9916,10 @@ xlog_redo(XLogReaderState *record) } /* ControlFile->checkPointCopy always tracks the latest ckpt XID */ + LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->checkPointCopy.nextXidEpoch = checkPoint.nextXidEpoch; ControlFile->checkPointCopy.nextXid = checkPoint.nextXid; + LWLockRelease(ControlFileLock); /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); @@ -9971,8 +9977,10 @@ xlog_redo(XLogReaderState *record) SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); /* ControlFile->checkPointCopy always tracks the latest ckpt XID */ + LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->checkPointCopy.nextXidEpoch = checkPoint.nextXidEpoch; ControlFile->checkPointCopy.nextXid = checkPoint.nextXid; + LWLockRelease(ControlFileLock); /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck);