zdev: Harden against invalid hypervisor data

Reduce chances of unintended side-effects when evaluating hypervisor
data which might have been corrupted.

Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zdev/include/sanitize.h

@@ -0,0 +1,32 @@
+/*
+ * zdev - Modify and display the persistent configuration of devices
+ *
+ * Copyright IBM Corp. 2026
+ *
+ * s390-tools is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#ifndef SANITIZE_H
+#define SANITIZE_H
+
+#include <ctype.h>
+#include <string.h>
+
+/* Valid control-program identifier special characters */
+#define VALID_CPNAME	"/"
+
+static inline int is_safe_char(unsigned char c, const char *set)
+{
+	return isalnum(c) || strchr(set, c);
+}
+
+static inline void sanitize(char *s, const char *set)
+{
+	for (; *s; s++) {
+		if (!is_safe_char((unsigned char)*s, set))
+			*s = '_';
+	}
+}
+
+#endif /* SANITIZE_H */