xen/intr: xen_intr_bind_isrc() always set handle

Previously the upper layer handle was being set before the last
potential error condition.  The reasoning appears to have been it was
assumed invalid in case of an error being returned.  Now ensure it is
invalid until just before a successful return.

Fixes: 76acc41fb7c7 ("Implement vector callback for PVHVM and unify event channel implementations")
Fixes: 6d54cab1fe7d ("xen: allow to register event channels without handlers")
Reviewed by: royger

1 files changed, 16 insertions, 18 deletions

diff --git a/sys/x86/xen/xen_intr.c b/sys/x86/xen/xen_intr.c
index 4b9b4675b5a0..167870b892f1 100644
--- a/sys/x86/xen/xen_intr.c
+++ b/sys/x86/xen/xen_intr.c
@@ -410,7 +410,7 @@ static int
 xen_intr_bind_isrc(struct xenisrc **isrcp, evtchn_port_t local_port,
     enum evtchn_type type, const char *intr_owner, driver_filter_t filter,
     driver_intr_t handler, void *arg, enum intr_type flags,
-    xen_intr_handle_t *port_handlep)
+    xen_intr_handle_t *const port_handlep)
 {
 	struct xenisrc *isrc;
 	int error;
@@ -420,6 +420,7 @@ xen_intr_bind_isrc(struct xenisrc **isrcp, evtchn_port_t local_port,
 		printf("%s: %s: Bad event handle\n", intr_owner, __func__);
 		return (EINVAL);
 	}
+	*port_handlep = NULL;
 
 	mtx_lock(&xen_intr_isrc_lock);
 	isrc = xen_intr_find_unused_isrc(type);
@@ -436,9 +437,6 @@ xen_intr_bind_isrc(struct xenisrc **isrcp, evtchn_port_t local_port,
 	refcount_init(&isrc->xi_refcount, 1);
 	mtx_unlock(&xen_intr_isrc_lock);
 
-	/* Assign the opaque handler */
-	*port_handlep = xen_intr_handle_from_isrc(isrc);
-
 #ifdef SMP
 	if (type == EVTCHN_TYPE_PORT) {
 		/*
@@ -450,23 +448,23 @@ xen_intr_bind_isrc(struct xenisrc **isrcp, evtchn_port_t local_port,
 	}
 #endif
 
-	if (filter == NULL && handler == NULL) {
-		/*
-		 * No filter/handler provided, leave the event channel
-		 * masked and without a valid handler, the caller is
-		 * in charge of setting that up.
-		 */
-		*isrcp = isrc;
-		return (0);
+	/*
+	 * If a filter or handler function is provided, add it to the event.
+	 * Otherwise the event channel is left masked and without a handler,
+	 * the caller is in charge of setting that up.
+	 */
+	if (filter != NULL || handler != NULL) {
+		error = xen_intr_add_handler(intr_owner, filter, handler, arg,
+		    flags, xen_intr_handle_from_isrc(isrc));
+		if (error != 0) {
+			xen_intr_release_isrc(isrc);
+			return (error);
+		}
 	}
 
-	error = xen_intr_add_handler(intr_owner, filter, handler, arg, flags,
-	    *port_handlep);
-	if (error != 0) {
-		xen_intr_release_isrc(isrc);
-		return (error);
-	}
 	*isrcp = isrc;
+	/* Assign the opaque handler */
+	*port_handlep = xen_intr_handle_from_isrc(isrc);
 	return (0);
 }