files: Fail dump if dump_one_file() fails

When dumping a process with a large number of open files,
dump_task_files_seized() processes the fds in batches. If
dump_one_file() results in an error, processing of the current batch is
stopped but the next batch (if any) will still be fetched and the error
value is overwritten. The result is a corrupt dump image (the fdinfo
file is missing a bunch of fds) which results in restore failure.

Also close all received fds after an error (previously the skipped ones
were left open).
Signed-off-by: Andy Tucker <agtucker@google.com>
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/files.c

@@ -606,7 +606,7 @@ int dump_task_files_seized(struct parasite_ctl *ctl, struct pstree_item *item,
 		goto err;
 
 	ret = 0; /* Don't fail if nr_fds == 0 */
-	for (off = 0; off < dfds->nr_fds; off += nr_fds) {
+	for (off = 0; ret == 0 && off < dfds->nr_fds; off += nr_fds) {
 		if (nr_fds + off > dfds->nr_fds)
 			nr_fds = dfds->nr_fds - off;
 
@@ -620,7 +620,6 @@ int dump_task_files_seized(struct parasite_ctl *ctl, struct pstree_item *item,
 
 			ret = dump_one_file(item->pid, dfds->fds[i + off],
 						lfds[i], opts + i, ctl, &e);
-			close(lfds[i]);
 			if (ret)
 				break;
 
@@ -628,6 +627,9 @@ int dump_task_files_seized(struct parasite_ctl *ctl, struct pstree_item *item,
 			if (ret)
 				break;
 		}
+
+		for (i = 0; i < nr_fds; i++)
+			close(lfds[i]);
 	}
 
 	pr_info("----------------------------------------\n");