media: v4l: event: Prevent freeing event subscriptions while accessed

[linux.git] / drivers / media / v4l2-core / v4l2-event.c

diff --git a/drivers/media/v4l2-core/v4l2-event.c b/drivers/media/v4l2-core/v4l2-event.c
index 127fe6eb91d9832289124a399b03b2d6c88715c3..a3ef1f50a4b3496dcfbe7cb4332a3bab9a3acc56 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-event.c
+++ b/drivers/media/v4l2-core/v4l2-event.c
@@ -115,14 +115,6 @@ static void __v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *e
        if (sev == NULL)
                return;
 
-       /*
-        * If the event has been added to the fh->subscribed list, but its
-        * add op has not completed yet elems will be 0, treat this as
-        * not being subscribed.
-        */
-       if (!sev->elems)
-               return;
-
        /* Increase event sequence number on fh. */
        fh->sequence++;
 
@@ -208,6 +200,7 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
        struct v4l2_subscribed_event *sev, *found_ev;
        unsigned long flags;
        unsigned i;
+       int ret = 0;
 
        if (sub->type == V4L2_EVENT_ALL)
                return -EINVAL;
@@ -225,31 +218,36 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
        sev->flags = sub->flags;
        sev->fh = fh;
        sev->ops = ops;
+       sev->elems = elems;
+
+       mutex_lock(&fh->subscribe_lock);
 
        spin_lock_irqsave(&fh->vdev->fh_lock, flags);
        found_ev = v4l2_event_subscribed(fh, sub->type, sub->id);
-       if (!found_ev)
-               list_add(&sev->list, &fh->subscribed);
        spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
 
        if (found_ev) {
+               /* Already listening */
                kvfree(sev);
-               return 0; /* Already listening */
+               goto out_unlock;
        }
 
        if (sev->ops && sev->ops->add) {
-               int ret = sev->ops->add(sev, elems);
+               ret = sev->ops->add(sev, elems);
                if (ret) {
-                       sev->ops = NULL;
-                       v4l2_event_unsubscribe(fh, sub);
-                       return ret;
+                       kvfree(sev);
+                       goto out_unlock;
                }
        }
 
-       /* Mark as ready for use */
-       sev->elems = elems;
+       spin_lock_irqsave(&fh->vdev->fh_lock, flags);
+       list_add(&sev->list, &fh->subscribed);
+       spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
 
-       return 0;
+out_unlock:
+       mutex_unlock(&fh->subscribe_lock);
+
+       return ret;
 }
 EXPORT_SYMBOL_GPL(v4l2_event_subscribe);
 
@@ -288,6 +286,8 @@ int v4l2_event_unsubscribe(struct v4l2_fh *fh,
                return 0;
        }
 
+       mutex_lock(&fh->subscribe_lock);
+
        spin_lock_irqsave(&fh->vdev->fh_lock, flags);
 
        sev = v4l2_event_subscribed(fh, sub->type, sub->id);
@@ -305,6 +305,8 @@ int v4l2_event_unsubscribe(struct v4l2_fh *fh,
        if (sev && sev->ops && sev->ops->del)
                sev->ops->del(sev);
 
+       mutex_unlock(&fh->subscribe_lock);
+
        kvfree(sev);
 
        return 0;