From 28ee04b537085148c75f575d2bc755a1fffc19c7 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Fri, 22 May 2020 16:23:59 +1200 Subject: [PATCH] Fix race condition 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. Back-patch to all supported release. Author: Nathan Bossart Discussion: https://postgr.es/m/70BF24D6-DC51-443F-B55A-95735803842A%40amazon.com --- src/backend/access/transam/xlog.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index ca09d81b08..274b808476 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -9976,7 +9976,9 @@ xlog_redo(XLogReaderState *record) } /* ControlFile->checkPointCopy always tracks the latest ckpt XID */ + LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->checkPointCopy.nextFullXid = checkPoint.nextFullXid; + LWLockRelease(ControlFileLock); /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); @@ -10033,7 +10035,9 @@ xlog_redo(XLogReaderState *record) SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB); /* ControlFile->checkPointCopy always tracks the latest ckpt XID */ + LWLockAcquire(ControlFileLock, LW_EXCLUSIVE); ControlFile->checkPointCopy.nextFullXid = checkPoint.nextFullXid; + LWLockRelease(ControlFileLock); /* Update shared-memory copy of checkpoint XID/epoch */ SpinLockAcquire(&XLogCtl->info_lck); -- 2.20.1