Re: [PULL 36/68] hw/misc/xlnx-versal-trng: Check returned bool in trng_prop_fault_event_set()

[Zhao Liu]

Hi Michael,

Thanks a lot and aslo this one, I forgot to update the status :/,
this patch has been merged (commit 1e0efa9735635,
"hw/misc/xlnx-versal-trng: Check returned bool in
trng_prop_fault_event_set()"). Sorry to make you
repeat the merge.

Best Regards,
Zhao


On Tue, Mar 12, 2024 at 06:27:22PM -0400, Michael S. Tsirkin wrote:
> Date: Tue, 12 Mar 2024 18:27:22 -0400
> From: "Michael S. Tsirkin" <mst@redhat.com>
> Subject: [PULL 36/68] hw/misc/xlnx-versal-trng: Check returned bool in
>  trng_prop_fault_event_set()
> X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1
> 
> 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.
> ...
> * 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.
> 
> But in trng_prop_fault_event_set, @errp is dereferenced without
> ERRP_GUARD():
> 
> visit_type_uint32(v, name, events, errp);
> if (*errp) {
>     return;
> }
> 
> Currently, since trng_prop_fault_event_set() doesn't get the NULL @errp
> parameter as a "set" method of object property, it hasn't triggered the
> bug that dereferencing the NULL @errp.
> 
> And since visit_type_uint32() returns bool, check the returned bool
> directly instead of dereferencing @errp, then we needn't the add missing
> ERRP_GUARD().
> 
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> Message-Id: <20240223085653.1255438-5-zhao1.liu@linux.intel.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  hw/misc/xlnx-versal-trng.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/hw/misc/xlnx-versal-trng.c b/hw/misc/xlnx-versal-trng.c
> index b8111b8b66..6495188dc7 100644
> --- a/hw/misc/xlnx-versal-trng.c
> +++ b/hw/misc/xlnx-versal-trng.c
> @@ -644,8 +644,7 @@ static void trng_prop_fault_event_set(Object *obj, 
> Visitor *v,
>      Property *prop = opaque;
>      uint32_t *events = object_field_prop_ptr(obj, prop);
>  
> -    visit_type_uint32(v, name, events, errp);
> -    if (*errp) {
> +    if (!visit_type_uint32(v, name, events, errp)) {
>          return;
>      }
>  
> -- 
> MST
>