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Fix locking bugs that could corrupt pg_control.

author Thomas Munro <tmunro@postgresql.org>

Mon, 8 Jun 2020 01:57:24 +0000 (13:57 +1200)

committer Thomas Munro <tmunro@postgresql.org>

Mon, 8 Jun 2020 01:57:24 +0000 (13:57 +1200)

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 <bossartn@amazon.com>
Author: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/70BF24D6-DC51-443F-B55A-95735803842A%40amazon.com

src/backend/access/transam/xlog.c patch | blob | blame | history

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c

index ca09d81b08cfeb885390650fe7da632a5b79504a..55cac186dc71fcc2f4628f9974b30850bb51eb5d 100644 (file)

--- a/src/backend/access/transam/xlog.c

+++ b/src/backend/access/transam/xlog.c

@@ -9743,6 +9743,8 @@ XLogReportParameters(void)

XLogFlush(recptr);

}

+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);

ControlFile->MaxConnections = MaxConnections;

ControlFile->max_worker_processes = max_worker_processes;

ControlFile->max_wal_senders = max_wal_senders;

@@ -9752,6 +9754,8 @@ XLogReportParameters(void)

ControlFile->wal_log_hints = wal_log_hints;

ControlFile->track_commit_timestamp = track_commit_timestamp;

UpdateControlFile();

+ LWLockRelease(ControlFileLock);

}

@@ -9976,7 +9980,9 @@ 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 +10039,9 @@ 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);

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