hw/intc: fix heap-buffer-overflow in rxicu_realize()

When &#39;j = icu->nr_sense – 1', the 'j < icu->nr_sense' condition is true,
then 'j = icu->nr_sense', the'icu->init_sense[j]' has out-of-bounds access.

The asan showed stack:
ERROR: AddressSanitizer: heap-buffer-overflow on address 0x604000004d7d at pc 0x55852cd26a76 bp 0x7ffe39f26200 sp 0x7ffe39f261f0
READ of size 1 at 0x604000004d7d thread T0
    #0 0x55852cd26a75 in rxicu_realize ../hw/intc/rx_icu.c:311
    #1 0x55852cf075f7 in device_set_realized ../hw/core/qdev.c:886
    #2 0x55852cd4a32f in property_set_bool ../qom/object.c:2251
    #3 0x55852cd4f9bb in object_property_set ../qom/object.c:1398
    #4 0x55852cd54f3f in object_property_set_qobject ../qom/qom-qobject.c:28
    #5 0x55852cd4fc3f in object_property_set_bool ../qom/object.c:1465
    #6 0x55852cbf0b27 in register_icu ../hw/rx/rx62n.c:156
    #7 0x55852cbf12a6 in rx62n_realize ../hw/rx/rx62n.c:261
    #8 0x55852cf075f7 in device_set_realized ../hw/core/qdev.c:886
    #9 0x55852cd4a32f in property_set_bool ../qom/object.c:2251
    #10 0x55852cd4f9bb in object_property_set ../qom/object.c:1398
    #11 0x55852cd54f3f in object_property_set_qobject ../qom/qom-qobject.c:28
    #12 0x55852cd4fc3f in object_property_set_bool ../qom/object.c:1465
    #13 0x55852cbf1a85 in rx_gdbsim_init ../hw/rx/rx-gdbsim.c:109
    #14 0x55852cd22de0 in qemu_init ../softmmu/vl.c:4380
    #15 0x55852ca57088 in main ../softmmu/main.c:49
    #16 0x7feefafa5d42 in __libc_start_main (/lib64/libc.so.6+0x26d42)

Add the 'ice->src[i].sense' initialize to the default value, and then
process init_sense array to identify which irqs should be level-triggered.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20201111141733.2358800-1-kuhn.chenqun@huawei.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/intc/rx_icu.c

@@ -300,22 +300,20 @@ static const MemoryRegionOps icu_ops = {
 static void rxicu_realize(DeviceState *dev, Error **errp)
 {
     RXICUState *icu = RX_ICU(dev);
-    int i, j;
+    int i;
 
     if (icu->init_sense == NULL) {
         qemu_log_mask(LOG_GUEST_ERROR,
                       "rx_icu: trigger-level property must be set.");
         return;
     }
-    for (i = j = 0; i < NR_IRQS; i++) {
-        if (icu->init_sense[j] == i) {
-            icu->src[i].sense = TRG_LEVEL;
-            if (j < icu->nr_sense) {
-                j++;
-            }
-        } else {
-            icu->src[i].sense = TRG_PEDGE;
-        }
+
+    for (i = 0; i < NR_IRQS; i++) {
+        icu->src[i].sense = TRG_PEDGE;
+    }
+    for (i = 0; i < icu->nr_sense; i++) {
+        uint8_t irqno = icu->init_sense[i];
+        icu->src[irqno].sense = TRG_LEVEL;
     }
     icu->req_irq = -1;
 }