If the event queue overflows when we are handling permission event, we
will never get response from userspace. So we must avoid waiting for it.
Change fsnotify_add_notify_event() to return whether overflow has
happened so that we can detect it in fanotify_handle_event() and act
accordingly.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/notify/fanotify/fanotify.c | 6 ++++--
fs/notify/notification.c | 14 ++++++++++----
2 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 0e792f5e3147..7564a070e6e8 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -192,10 +192,12 @@ static int fanotify_handle_event(struct fsnotify_group *group,
ret = fsnotify_add_notify_event(group, fsn_event, fanotify_merge);
if (ret) {
- BUG_ON(mask & FAN_ALL_PERM_EVENTS);
+ /* Permission events shouldn't be merged */
+ BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
/* Our event wasn't used in the end. Free it. */
fsnotify_destroy_event(group, fsn_event);
- ret = 0;
+
+ return 0;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index 6bec2f4918f9..6a4ba17c0395 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -80,7 +80,8 @@ void fsnotify_destroy_event(struct fsnotify_group *group,
/*
* Add an event to the group notification queue. The group can later pull this
* event off the queue to deal with. The function returns 0 if the event was
- * added to the queue, 1 if the event was merged with some other queued event.
+ * added to the queue, 1 if the event was merged with some other queued event,
+ * 2 if the queue of events has overflown.
*/
int fsnotify_add_notify_event(struct fsnotify_group *group,
struct fsnotify_event *event,
@@ -95,10 +96,14 @@ int fsnotify_add_notify_event(struct fsnotify_group *group,
mutex_lock(&group->notification_mutex);
if (group->q_len >= group->max_events) {
+ ret = 2;
/* Queue overflow event only if it isn't already queued */
- if (list_empty(&group->overflow_event.list))
- event = &group->overflow_event;
- ret = 1;
+ if (!list_empty(&group->overflow_event.list)) {
+ mutex_unlock(&group->notification_mutex);
+ return ret;
+ }
+ event = &group->overflow_event;
+ goto queue;
}
if (!list_empty(list) && merge) {
@@ -109,6 +114,7 @@ int fsnotify_add_notify_event(struct fsnotify_group *group,
}
}
+queue:
group->q_len++;
list_add_tail(&event->list, list);
mutex_unlock(&group->notification_mutex);
--
1.8.1.4
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