From 496f98c088f9f00d3592387953928cf3480828e6 Mon Sep 17 00:00:00 2001 From: Sakari Ailus Date: Mon, 5 Nov 2018 09:35:44 -0500 Subject: [PATCH] media: v4l: event: Add subscription to list before calling "add" operation commit 92539d3eda2c090b382699bbb896d4b54e9bdece upstream. Patch ad608fbcf166 changed how events were subscribed to address an issue elsewhere. As a side effect of that change, the "add" callback was called before the event subscription was added to the list of subscribed events, causing the first event queued by the add callback (and possibly other events arriving soon afterwards) to be lost. Fix this by adding the subscription to the list before calling the "add" callback, and clean up afterwards if that fails. Fixes: ad608fbcf166 ("media: v4l: event: Prevent freeing event subscriptions while accessed") Reported-by: Dave Stevenson Signed-off-by: Sakari Ailus Tested-by: Dave Stevenson Reviewed-by: Hans Verkuil Tested-by: Hans Verkuil Cc: stable@vger.kernel.org (for 4.14 and up) Signed-off-by: Mauro Carvalho Chehab [Sakari Ailus: Backported to v4.9 stable] Signed-off-by: Sakari Ailus Signed-off-by: Greg Kroah-Hartman --- drivers/media/v4l2-core/v4l2-event.c | 43 ++++++++++++++++------------ 1 file changed, 24 insertions(+), 19 deletions(-) diff --git a/drivers/media/v4l2-core/v4l2-event.c b/drivers/media/v4l2-core/v4l2-event.c index 567d86835f00..1fda2873375f 100644 --- a/drivers/media/v4l2-core/v4l2-event.c +++ b/drivers/media/v4l2-core/v4l2-event.c @@ -197,6 +197,22 @@ int v4l2_event_pending(struct v4l2_fh *fh) } EXPORT_SYMBOL_GPL(v4l2_event_pending); +static void __v4l2_event_unsubscribe(struct v4l2_subscribed_event *sev) +{ + struct v4l2_fh *fh = sev->fh; + unsigned int i; + + lockdep_assert_held(&fh->subscribe_lock); + assert_spin_locked(&fh->vdev->fh_lock); + + /* Remove any pending events for this subscription */ + for (i = 0; i < sev->in_use; i++) { + list_del(&sev->events[sev_pos(sev, i)].list); + fh->navailable--; + } + list_del(&sev->list); +} + int v4l2_event_subscribe(struct v4l2_fh *fh, const struct v4l2_event_subscription *sub, unsigned elems, const struct v4l2_subscribed_event_ops *ops) @@ -228,27 +244,23 @@ int v4l2_event_subscribe(struct v4l2_fh *fh, 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 */ kfree(sev); - goto out_unlock; - } - - if (sev->ops && sev->ops->add) { + } else if (sev->ops && sev->ops->add) { ret = sev->ops->add(sev, elems); if (ret) { + spin_lock_irqsave(&fh->vdev->fh_lock, flags); + __v4l2_event_unsubscribe(sev); + spin_unlock_irqrestore(&fh->vdev->fh_lock, flags); kfree(sev); - goto out_unlock; } } - spin_lock_irqsave(&fh->vdev->fh_lock, flags); - list_add(&sev->list, &fh->subscribed); - spin_unlock_irqrestore(&fh->vdev->fh_lock, flags); - -out_unlock: mutex_unlock(&fh->subscribe_lock); return ret; @@ -283,7 +295,6 @@ int v4l2_event_unsubscribe(struct v4l2_fh *fh, { struct v4l2_subscribed_event *sev; unsigned long flags; - int i; if (sub->type == V4L2_EVENT_ALL) { v4l2_event_unsubscribe_all(fh); @@ -295,14 +306,8 @@ int v4l2_event_unsubscribe(struct v4l2_fh *fh, spin_lock_irqsave(&fh->vdev->fh_lock, flags); sev = v4l2_event_subscribed(fh, sub->type, sub->id); - if (sev != NULL) { - /* Remove any pending events for this subscription */ - for (i = 0; i < sev->in_use; i++) { - list_del(&sev->events[sev_pos(sev, i)].list); - fh->navailable--; - } - list_del(&sev->list); - } + if (sev != NULL) + __v4l2_event_unsubscribe(sev); spin_unlock_irqrestore(&fh->vdev->fh_lock, flags); -- 2.20.1