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commit    ae9da357bd6d3f553c9d2a148a97f4db35bc608d
Author:   Thomas Munro <tmunro@postgresql.org>
Date:     Sun Oct 15 21:43:47 2023 +0000
First released in: 17.0, 11.22, 12.17, 13.13, 14.10, 15.5, 16.1

    Acquire ControlFileLock in relevant SQL functions.
    
    Commit dc7d70ea added functions that read the control file, but didn't
    acquire ControlFileLock.  With unlucky timing, file systems that have
    weak interlocking like ext4 and ntfs could expose partially overwritten
    contents, and the checksum would fail.
    
    Back-patch to all supported releases.
    
    Reviewed-by: David Steele <david@pgmasters.net>
    Reviewed-by: Anton A. Melnikov <aamelnikov@inbox.ru>
    Reviewed-by: Michael Paquier <michael@paquier.xyz>
    Discussion: https://postgr.es/m/20221123014224.xisi44byq3cf5psi%40awork3.anarazel.de


 src/backend/utils/misc/pg_controldata.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/backend/utils/misc/pg_controldata.c b/src/backend/utils/misc/pg_controldata.c
index 419b58330fe..da61c16fc9a 100644
--- a/src/backend/utils/misc/pg_controldata.c
+++ b/src/backend/utils/misc/pg_controldata.c
@@ -24,6 +24,7 @@
 #include "common/controldata_utils.h"
 #include "funcapi.h"
 #include "miscadmin.h"
+#include "storage/lwlock.h"
 #include "utils/builtins.h"
 #include "utils/pg_lsn.h"
 #include "utils/timestamp.h"
@@ -54,7 +55,9 @@ pg_control_system(PG_FUNCTION_ARGS)
 	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* read the control file */
+	LWLockAcquire(ControlFileLock, LW_SHARED);
 	ControlFile = get_controlfile(DataDir, &crc_ok);
+	LWLockRelease(ControlFileLock);
 	if (!crc_ok)
 		ereport(ERROR,
 				(errmsg("calculated CRC checksum does not match value stored in file")));
@@ -132,7 +135,9 @@ pg_control_checkpoint(PG_FUNCTION_ARGS)
 	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* Read the control file. */
+	LWLockAcquire(ControlFileLock, LW_SHARED);
 	ControlFile = get_controlfile(DataDir, &crc_ok);
+	LWLockRelease(ControlFileLock);
 	if (!crc_ok)
 		ereport(ERROR,
 				(errmsg("calculated CRC checksum does not match value stored in file")));
@@ -235,7 +240,9 @@ pg_control_recovery(PG_FUNCTION_ARGS)
 	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* read the control file */
+	LWLockAcquire(ControlFileLock, LW_SHARED);
 	ControlFile = get_controlfile(DataDir, &crc_ok);
+	LWLockRelease(ControlFileLock);
 	if (!crc_ok)
 		ereport(ERROR,
 				(errmsg("calculated CRC checksum does not match value stored in file")));
@@ -300,7 +307,9 @@ pg_control_init(PG_FUNCTION_ARGS)
 	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* read the control file */
+	LWLockAcquire(ControlFileLock, LW_SHARED);
 	ControlFile = get_controlfile(DataDir, &crc_ok);
+	LWLockRelease(ControlFileLock);
 	if (!crc_ok)
 		ereport(ERROR,
 				(errmsg("calculated CRC checksum does not match value stored in file")));


[parent: 6fd1dbdb21cb]