[PATCH 4/6] hw/misc/xlnx-versal-trng: Fix missing ERRP_GUARD() in trng_prop_fault_event_set()

[Zhao Liu]

From: Zhao Liu <zhao1.liu@intel.com>

As the comment in qapi/error, dereferencing @errp requires
ERRP_GUARD():

* = Why, when and how to use ERRP_GUARD() =
*
* Without ERRP_GUARD(), use of the @errp parameter is restricted:
* - It must not be dereferenced, because it may be null.
* - It should not be passed to error_prepend() or
*   error_append_hint(), because that doesn't work with &error_fatal.
* ERRP_GUARD() lifts these restrictions.
*
* To use ERRP_GUARD(), add it right at the beginning of the function.
* @errp can then be used without worrying about the argument being
* NULL or &error_fatal.
*
* Using it when it's not needed is safe, but please avoid cluttering
* the source with useless code.

Currently, since trng_prop_fault_event_set() doesn't get the NULL errp
parameter as a "set" method of object property, it doesn't trigger the
dereference issue.

To follow the requirement of errp, add missing ERRP_GUARD() in
trng_prop_fault_event_set().

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
Suggested by credit:
 Markus: Referred his explanation about ERRP_GUARD().
---
 hw/misc/xlnx-versal-trng.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/misc/xlnx-versal-trng.c b/hw/misc/xlnx-versal-trng.c
index b8111b8b6626..3579348a9d17 100644
--- a/hw/misc/xlnx-versal-trng.c
+++ b/hw/misc/xlnx-versal-trng.c
@@ -33,6 +33,7 @@
 #include "qemu/error-report.h"
 #include "qemu/guest-random.h"
 #include "qemu/timer.h"
+#include "qapi/error.h"
 #include "qapi/visitor.h"
 #include "migration/vmstate.h"
 #include "hw/qdev-properties.h"
@@ -641,6 +642,7 @@ static void trng_prop_fault_event_set(Object *obj, Visitor 
*v,
                                       const char *name, void *opaque,
                                       Error **errp)
 {
+    ERRP_GUARD();
     Property *prop = opaque;
     uint32_t *events = object_field_prop_ptr(obj, prop);
 
-- 
2.34.1