util/aio-win32: Correct the event array size in aio_poll()

WaitForMultipleObjects() can only wait for MAXIMUM_WAIT_OBJECTS
object handles. Correct the event array size in aio_poll() and
add a assert() to ensure it does not cause out of bound access.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20221019102015.2441622-3-bmeng.cn@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

util/aio-win32.c

@@ -326,9 +326,9 @@ void aio_dispatch(AioContext *ctx)
 bool aio_poll(AioContext *ctx, bool blocking)
 {
     AioHandler *node;
-    HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
+    HANDLE events[MAXIMUM_WAIT_OBJECTS];
     bool progress, have_select_revents, first;
-    int count;
+    unsigned count;
     int timeout;
 
     /*
@@ -369,6 +369,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
     QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
         if (!node->deleted && node->io_notify
             && aio_node_check(ctx, node->is_external)) {
+            assert(count < MAXIMUM_WAIT_OBJECTS);
             events[count++] = event_notifier_get_handle(node->e);
         }
     }