diff --git a/extra/mariabackup/xtrabackup.cc b/extra/mariabackup/xtrabackup.cc
index 96c90b5afad..64a0f44e183 100644
--- a/extra/mariabackup/xtrabackup.cc
+++ b/extra/mariabackup/xtrabackup.cc
@@ -4503,14 +4503,21 @@ bool Backup_datasinks::backup_low()
 
 		if (recv_find_max_checkpoint(&max_cp_field) == DB_SUCCESS
 		    && log_sys.log.format != 0) {
-			if (max_cp_field == LOG_CHECKPOINT_1) {
-				log_header_read(max_cp_field);
+			switch (max_cp_field) {
+			case LOG_CHECKPOINT_1:
+				if (log_header_read(max_cp_field)) {
+					/* metadata_to_lsn still 0 so error returns below */
+					msg("Error: recv_find_max_checkpoint() failed.");
+					break;
+				}
+				/* fallthrough */
+			default:
+				metadata_to_lsn = mach_read_from_8(
+					log_sys.checkpoint_buf + LOG_CHECKPOINT_LSN);
+				msg("mariabackup: The latest check point"
+				    " (for incremental): '" LSN_PF "'",
+				    metadata_to_lsn);
 			}
-			metadata_to_lsn = mach_read_from_8(
-				log_sys.checkpoint_buf + LOG_CHECKPOINT_LSN);
-			msg("mariabackup: The latest check point"
-			    " (for incremental): '" LSN_PF "'",
-			    metadata_to_lsn);
 		} else {
 			msg("Error: recv_find_max_checkpoint() failed.");
 		}
@@ -4721,7 +4728,11 @@ reread_log_header:
 	checkpoint_lsn_start = log_sys.log.get_lsn();
 	checkpoint_no_start = log_sys.next_checkpoint_no;
 
-	log_header_read(max_cp_field);
+	if (log_header_read(max_cp_field)) {
+		log_mutex_exit();
+		goto fail;
+	}
+
 
 	if (checkpoint_no_start != mach_read_from_8(buf + LOG_CHECKPOINT_NO)
 	    || checkpoint_lsn_start
diff --git a/mysql-test/suite/mariabackup/data_directory.result b/mysql-test/suite/mariabackup/data_directory.result
index 4e45127bd6a..8692c35239e 100644
--- a/mysql-test/suite/mariabackup/data_directory.result
+++ b/mysql-test/suite/mariabackup/data_directory.result
@@ -11,3 +11,9 @@ SELECT * FROM t;
 a
 1
 DROP TABLE t;
+#
+# MDEV-18200 MariaBackup full backup failed with InnoDB: Failing assertion: success
+#
+#
+# End of 10.4 tests
+#
diff --git a/mysql-test/suite/mariabackup/data_directory.test b/mysql-test/suite/mariabackup/data_directory.test
index a89b7bdccc4..ffb3ab3073c 100644
--- a/mysql-test/suite/mariabackup/data_directory.test
+++ b/mysql-test/suite/mariabackup/data_directory.test
@@ -21,4 +21,19 @@ rmdir $table_data_dir;
 SELECT * FROM t;
 DROP TABLE t;
 rmdir $targetdir;
+
+--echo #
+--echo # MDEV-18200 MariaBackup full backup failed with InnoDB: Failing assertion: success
+--echo #
+let $DATADIR= `select @@datadir`;
+chmod 0000 $DATADIR/ibdata1;
+--disable_result_log
+--error 1
+exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf --backup --target-dir=$targetdir;
+--enable_result_log
+chmod 0755 $DATADIR/ibdata1;
 rmdir $table_data_dir;
+rmdir $targetdir;
+--echo #
+--echo # End of 10.4 tests
+--echo #
diff --git a/plugin/cracklib_password_check/CMakeLists.txt b/plugin/cracklib_password_check/CMakeLists.txt
index 4a6337310f9..79b3b80fbef 100644
--- a/plugin/cracklib_password_check/CMakeLists.txt
+++ b/plugin/cracklib_password_check/CMakeLists.txt
@@ -1,3 +1,9 @@
+
+IF(PLUGIN_CRACKLIB_PASSWORD_CHECK STREQUAL "NO")
+  ADD_FEATURE_INFO(CRACKLIB_PASSWORD_CHECK "OFF" "CrackLib Password Validation Plugin")
+  RETURN()
+ENDIF()
+
 INCLUDE (CheckIncludeFiles)
 INCLUDE (CheckLibraryExists)
 
diff --git a/storage/innobase/fil/fil0fil.cc b/storage/innobase/fil/fil0fil.cc
index ebeb1f66101..45f8c341ee2 100644
--- a/storage/innobase/fil/fil0fil.cc
+++ b/storage/innobase/fil/fil0fil.cc
@@ -557,7 +557,9 @@ fail:
 			&success);
 	}
 
-	ut_a(success);
+	if (!success)
+		return false;
+
 	ut_a(node->is_open());
 
 	fil_system.n_open++;
@@ -4062,8 +4064,10 @@ inline void IORequest::set_fil_node(fil_node_t* node)
 @param[in] message	message for aio handler if non-sync aio
 			used, else ignored
 @param[in] ignore_missing_space true=ignore missing space duging read
-@return DB_SUCCESS, or DB_TABLESPACE_DELETED
-	if we are trying to do i/o on a tablespace which does not exist */
+@retval DB_SUCCESS, if successful; or
+@retval DB_IO_ERROR, if unable to open file or the purpose==FIL_TYPE_IMPORT; or
+@retval DB_TABLESPACE_DELETED, if we are trying to do i/o on a tablespace which
+        does not exist */
 dberr_t
 fil_io(
 	const IORequest&	type,
@@ -4232,11 +4236,13 @@ fil_io(
 			return(DB_TABLESPACE_DELETED);
 		}
 
-		/* The tablespace is for log. Currently, we just assert here
+		/* The tablespace is for log. We used to asssert here
 		to prevent handling errors along the way fil_io returns.
 		Also, if the log files are missing, it would be hard to
-		promise the server can continue running. */
-		ut_a(0);
+		promise the server can continue running. However this
+		is also used by MariaDB-backup, so we need to handle it. */
+		mutex_exit(&fil_system.mutex);
+		return(DB_IO_ERROR);
 	}
 
 	/* Check that at least the start offset is within the bounds of a
diff --git a/storage/innobase/include/log0log.h b/storage/innobase/include/log0log.h
index 477bb0a1d05..7079479754f 100644
--- a/storage/innobase/include/log0log.h
+++ b/storage/innobase/include/log0log.h
@@ -209,8 +209,9 @@ void
 logs_empty_and_mark_files_at_shutdown(void);
 /*=======================================*/
 /** Read a log group header page to log_sys.checkpoint_buf.
-@param[in]	header	0 or LOG_CHECKPOINT_1 or LOG_CHECKPOINT2 */
-void log_header_read(ulint header);
+@param[in]	header	0 or LOG_CHECKPOINT_1 or LOG_CHECKPOINT2
+@return error code (from fil_io) or DB_SUCCESS */
+dberr_t log_header_read(ulint header);
 /** Write checkpoint info to the log header and invoke log_mutex_exit().
 @param[in]	sync	whether to wait for the write to complete
 @param[in]	end_lsn	start LSN of the MLOG_CHECKPOINT mini-transaction */
diff --git a/storage/innobase/log/log0log.cc b/storage/innobase/log/log0log.cc
index bf75b3b7c86..433483b662e 100644
--- a/storage/innobase/log/log0log.cc
+++ b/storage/innobase/log/log0log.cc
@@ -1355,20 +1355,21 @@ log_group_checkpoint(lsn_t end_lsn)
 }
 
 /** Read a log group header page to log_sys.checkpoint_buf.
-@param[in]	header	0 or LOG_CHECKPOINT_1 or LOG_CHECKPOINT2 */
-void log_header_read(ulint header)
+@param[in]	header	0 or LOG_CHECKPOINT_1 or LOG_CHECKPOINT2
+@return         DB_SUCCESS or error. */
+dberr_t log_header_read(ulint header)
 {
-	ut_ad(log_mutex_own());
+  ut_ad(log_mutex_own());
 
-	log_sys.n_log_ios++;
+  log_sys.n_log_ios++;
 
-	MONITOR_INC(MONITOR_LOG_IO);
+  MONITOR_INC(MONITOR_LOG_IO);
 
-	fil_io(IORequestLogRead, true,
-	       page_id_t(SRV_LOG_SPACE_FIRST_ID,
-			 header >> srv_page_size_shift),
-	       0, header & (srv_page_size - 1),
-	       OS_FILE_LOG_BLOCK_SIZE, log_sys.checkpoint_buf, NULL);
+  return fil_io(IORequestLogRead, true,
+                page_id_t(SRV_LOG_SPACE_FIRST_ID,
+                          header >> srv_page_size_shift),
+                0, header & (srv_page_size - 1),
+                OS_FILE_LOG_BLOCK_SIZE, log_sys.checkpoint_buf, NULL);
 }
 
 /** Write checkpoint info to the log header and invoke log_mutex_exit().
diff --git a/storage/innobase/log/log0recv.cc b/storage/innobase/log/log0recv.cc
index eb4cb910679..5645e56903d 100644
--- a/storage/innobase/log/log0recv.cc
+++ b/storage/innobase/log/log0recv.cc
@@ -1068,6 +1068,7 @@ recv_find_max_checkpoint_0(ulint* max_field)
 {
 	ib_uint64_t	max_no = 0;
 	ib_uint64_t	checkpoint_no;
+	dberr_t		err;
 	byte*		buf	= log_sys.checkpoint_buf;
 
 	ut_ad(log_sys.log.format == 0);
@@ -1085,7 +1086,8 @@ recv_find_max_checkpoint_0(ulint* max_field)
 
 	for (ulint field = LOG_CHECKPOINT_1; field <= LOG_CHECKPOINT_2;
 	     field += LOG_CHECKPOINT_2 - LOG_CHECKPOINT_1) {
-		log_header_read(field);
+		if ((err= log_header_read(field)))
+			return err;
 
 		if (static_cast<uint32_t>(ut_fold_binary(buf, CHECKSUM_1))
 		    != mach_read_from_4(buf + CHECKSUM_1)
@@ -1208,13 +1210,15 @@ recv_find_max_checkpoint(ulint* max_field)
 	ib_uint64_t	checkpoint_no;
 	ulint		field;
 	byte*		buf;
+	dberr_t		err;
 
 	max_no = 0;
 	*max_field = 0;
 
 	buf = log_sys.checkpoint_buf;
 
-	log_header_read(0);
+	if ((err= log_header_read(0)))
+		return err;
 	/* Check the header page checksum. There was no
 	checksum in the first redo log format (version 0). */
 	log_sys.log.format = mach_read_from_4(buf + LOG_HEADER_FORMAT);
@@ -1252,7 +1256,8 @@ recv_find_max_checkpoint(ulint* max_field)
 	for (field = LOG_CHECKPOINT_1; field <= LOG_CHECKPOINT_2;
 	     field += LOG_CHECKPOINT_2 - LOG_CHECKPOINT_1) {
 
-		log_header_read(field);
+		if ((err= log_header_read(field)))
+			return err;
 
 		const ulint crc32 = log_block_calc_checksum_crc32(buf);
 		const ulint cksum = log_block_get_checksum(buf);
@@ -3630,7 +3635,8 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 		return(err);
 	}
 
-	log_header_read(max_cp_field);
+	if ((err= log_header_read(max_cp_field)))
+		return err;
 
 	buf = log_sys.checkpoint_buf;