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commit    606be8a35d9726b6c0468428b6262e58d9e308af
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 781f8b87580..fe52cffbf40 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: 782be0f7124a]