MDEV-9549: Trying to decrypt a not encrypted page

Make sure that on decrypt we do not try to reference
NULL pointer and if page contains undefined
FIL_PAGE_FILE_FLUSH_LSN field on when page is not
the first page or page is not in system tablespace,
clear it.

storage/innobase/fil/fil0crypt.cc

@@ -712,21 +712,37 @@ fil_space_decrypt(
 	ulint page_type = mach_read_from_2(src_frame+FIL_PAGE_TYPE);
 	uint key_version = mach_read_from_4(src_frame + FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION);
 	bool page_compressed = (page_type == FIL_PAGE_PAGE_COMPRESSED_ENCRYPTED);
-
+	ulint offset = mach_read_from_4(src_frame + FIL_PAGE_OFFSET);
+	ulint space = mach_read_from_4(src_frame + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
+	ib_uint64_t lsn = mach_read_from_8(src_frame + FIL_PAGE_LSN);
 	*err = DB_SUCCESS;
 
 	if (key_version == ENCRYPTION_KEY_NOT_ENCRYPTED) {
 		return false;
 	}
 
-	ut_ad(crypt_data->encryption != FIL_SPACE_ENCRYPTION_OFF);
+	if (crypt_data == NULL) {
+		if (space != 0 && offset != 0 && key_version != 0) {
+			/* FIL_PAGE_FILE_FLUSH_LSN field i.e.
+			FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION
+			should be only defined for the
+			first page in a system tablespace
+			data file (ibdata*, not *.ibd), if not
+			clear it. */
+#ifdef UNIV_DEBUG
+			ib_logf(IB_LOG_LEVEL_WARN,
+				"Page on space %lu offset %lu has key_version %u"
+				" when it shoud be undefined.",
+				space, offset, key_version);
+#endif
+			mach_write_to_4(src_frame + FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION, 0);
+		}
+		return false;
+	}
 
-	/* read space & offset & lsn */
-	ulint space = mach_read_from_4(
-		src_frame + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
-	ulint offset = mach_read_from_4(
-		src_frame + FIL_PAGE_OFFSET);
-	ib_uint64_t lsn = mach_read_from_8(src_frame + FIL_PAGE_LSN);
+	ut_ad(crypt_data != NULL && crypt_data->encryption != FIL_SPACE_ENCRYPTION_OFF);
+
+	/* read space & lsn */
 	ulint header_len = FIL_PAGE_DATA;
 
 	if (page_compressed) {

storage/xtradb/fil/fil0crypt.cc

@@ -712,21 +712,37 @@ fil_space_decrypt(
 	ulint page_type = mach_read_from_2(src_frame+FIL_PAGE_TYPE);
 	uint key_version = mach_read_from_4(src_frame + FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION);
 	bool page_compressed = (page_type == FIL_PAGE_PAGE_COMPRESSED_ENCRYPTED);
-
+	ulint offset = mach_read_from_4(src_frame + FIL_PAGE_OFFSET);
+	ulint space = mach_read_from_4(src_frame + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
+	ib_uint64_t lsn = mach_read_from_8(src_frame + FIL_PAGE_LSN);
 	*err = DB_SUCCESS;
 
 	if (key_version == ENCRYPTION_KEY_NOT_ENCRYPTED) {
 		return false;
 	}
 
-	ut_ad(crypt_data->encryption != FIL_SPACE_ENCRYPTION_OFF);
+	if (crypt_data == NULL) {
+		if (space != 0 && offset != 0 && key_version != 0) {
+			/* FIL_PAGE_FILE_FLUSH_LSN field i.e.
+			FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION
+			should be only defined for the
+			first page in a system tablespace
+			data file (ibdata*, not *.ibd), if not
+			clear it. */
+#ifdef UNIV_DEBUG
+			ib_logf(IB_LOG_LEVEL_WARN,
+				"Page on space %lu offset %lu has key_version %u"
+				" when it shoud be undefined.",
+				space, offset, key_version);
+#endif
+			mach_write_to_4(src_frame + FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION, 0);
+		}
+		return false;
+	}
 
-	/* read space & offset & lsn */
-	ulint space = mach_read_from_4(
-		src_frame + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
-	ulint offset = mach_read_from_4(
-		src_frame + FIL_PAGE_OFFSET);
-	ib_uint64_t lsn = mach_read_from_8(src_frame + FIL_PAGE_LSN);
+	ut_ad(crypt_data != NULL && crypt_data->encryption != FIL_SPACE_ENCRYPTION_OFF);
+
+	/* read space & lsn */
 	ulint header_len = FIL_PAGE_DATA;
 
 	if (page_compressed) {