Add validation for WAL segment size in pg_control.

This serves as an additional sanity check to be sure the pg_control format is as expected. The field is useful for being near the end and containing a limited number of discrete values.

src/postgres/interface.c

@@ -180,6 +180,14 @@ pgWalSegmentSizeCheck(unsigned int pgVersion, unsigned int walSegmentSize)
             PG_WAL_SEGMENT_SIZE_DEFAULT);
     }
 
+    // Check that the WAL segment size is valid
+    if (!IsValidWalSegSize(walSegmentSize))
+    {
+        THROW_FMT(
+            FormatError, "wal segment size is %u but must be a power of two between %d and %d inclusive", walSegmentSize,
+            WalSegMinSize, WalSegMaxSize);
+    }
+
     FUNCTION_TEST_RETURN_VOID();
 }
 

src/postgres/interface/static.vendor.h

@@ -244,4 +244,22 @@ Types from src/include/access/transam.h
  */
 #define FirstNormalObjectId		16384
 
+/***********************************************************************************************************************************
+Types from src/include/access/xlog_internal.h
+***********************************************************************************************************************************/
+
+// WalSegMinSize/WalSegMinSize macros
+// ---------------------------------------------------------------------------------------------------------------------------------
+/* wal_segment_size can range from 1MB to 1GB */
+#define WalSegMinSize 1024 * 1024
+#define WalSegMaxSize 1024 * 1024 * 1024
+
+// IsPowerOf2/IsValidWalSegSize macros
+// ---------------------------------------------------------------------------------------------------------------------------------
+/* check that the given size is a valid wal_segment_size */
+#define IsPowerOf2(x) (x > 0 && ((x) & ((x)-1)) == 0)
+#define IsValidWalSegSize(size) \
+	 (IsPowerOf2(size) && \
+	 ((size) >= WalSegMinSize && (size) <= WalSegMaxSize))
+
 #endif

test/src/common/harnessPostgres.c

@@ -193,7 +193,9 @@ hrnPgControlToBuffer(const unsigned int controlVersion, const unsigned int crc,
 
     // Set defaults if values are not passed
     pgControl.pageSize = pgControl.pageSize == 0 ? pgPageSize8 : pgControl.pageSize;
-    pgControl.walSegmentSize = pgControl.walSegmentSize == 0 ? PG_WAL_SEGMENT_SIZE_DEFAULT : pgControl.walSegmentSize;
+    pgControl.walSegmentSize =
+        pgControl.walSegmentSize == UINT_MAX ?
+            0 : (pgControl.walSegmentSize == 0 ? PG_WAL_SEGMENT_SIZE_DEFAULT : pgControl.walSegmentSize);
     pgControl.catalogVersion =
         pgControl.catalogVersion == 0 ? hrnPgInterfaceVersion(pgControl.version)->catalogVersion() : pgControl.catalogVersion;
     pgControl.systemId = pgControl.systemId < 100 ? hrnPgSystemId(pgControl.version) + pgControl.systemId : pgControl.systemId;

test/src/module/postgres/interfaceTest.c

@@ -127,6 +127,31 @@ testRun(void)
             pgControlFromFile(storageTest, NULL), FormatError,
             "wal segment size is 1048576 but must be 16777216 for PostgreSQL <= 10");
 
+        // -------------------------------------------------------------------------------------------------------------------------
+        HRN_PG_CONTROL_PUT(storageTest, PG_VERSION_11, .walSegmentSize = UINT_MAX); // UINT_MAX forces size to 0
+
+        TEST_ERROR(
+            pgControlFromFile(storageTest, NULL), FormatError,
+            "wal segment size is 0 but must be a power of two between 1048576 and 1073741824 inclusive");
+
+        HRN_PG_CONTROL_PUT(storageTest, PG_VERSION_11, .walSegmentSize = 1);
+
+        TEST_ERROR(
+            pgControlFromFile(storageTest, NULL), FormatError,
+            "wal segment size is 1 but must be a power of two between 1048576 and 1073741824 inclusive");
+
+        HRN_PG_CONTROL_PUT(storageTest, PG_VERSION_11, .walSegmentSize = 47);
+
+        TEST_ERROR(
+            pgControlFromFile(storageTest, NULL), FormatError,
+            "wal segment size is 47 but must be a power of two between 1048576 and 1073741824 inclusive");
+
+        HRN_PG_CONTROL_PUT(storageTest, PG_VERSION_11, .walSegmentSize = (unsigned int)2 * 1024 * 1024 * 1024);
+
+        TEST_ERROR(
+            pgControlFromFile(storageTest, NULL), FormatError,
+            "wal segment size is 2147483648 but must be a power of two between 1048576 and 1073741824 inclusive");
+
         // -------------------------------------------------------------------------------------------------------------------------
         HRN_PG_CONTROL_PUT(storageTest, PG_VERSION_95, .pageSize = 64 * 1024);