fsnotify: Do not return merged event from fsnotify_add_notify_event()
The event returned from fsnotify_add_notify_event() cannot ever be used
safely as the event may be freed by the time the function returns (after
dropping notification_mutex). So change the prototype to just return
whether the event was added or merged into some existing event.
Reported-and-tested-by: Jiri Kosina <jkosina@suse.cz>
Reported-and-tested-by: Dave Jones <davej@fedoraproject.org>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index cc78e2f..c7e5e8f 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -28,8 +28,7 @@
}
/* and the list better be locked by something too! */
-static struct fsnotify_event *fanotify_merge(struct list_head *list,
- struct fsnotify_event *event)
+static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
{
struct fsnotify_event *test_event;
bool do_merge = false;
@@ -43,7 +42,7 @@
* one we should check for permission response.
*/
if (event->mask & FAN_ALL_PERM_EVENTS)
- return NULL;
+ return 0;
#endif
list_for_each_entry_reverse(test_event, list, list) {
@@ -54,10 +53,10 @@
}
if (!do_merge)
- return NULL;
+ return 0;
test_event->mask |= event->mask;
- return test_event;
+ return 1;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
@@ -153,7 +152,6 @@
int ret = 0;
struct fanotify_event_info *event;
struct fsnotify_event *fsn_event;
- struct fsnotify_event *notify_fsn_event;
BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
@@ -192,13 +190,11 @@
event->response = 0;
#endif
- notify_fsn_event = fsnotify_add_notify_event(group, fsn_event,
- fanotify_merge);
- if (notify_fsn_event) {
+ ret = fsnotify_add_notify_event(group, fsn_event, fanotify_merge);
+ if (ret) {
/* Our event wasn't used in the end. Free it. */
fsnotify_destroy_event(group, fsn_event);
- if (IS_ERR(notify_fsn_event))
- return PTR_ERR(notify_fsn_event);
+ ret = 0;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index aad1a35..d5ee563 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -53,15 +53,13 @@
return false;
}
-static struct fsnotify_event *inotify_merge(struct list_head *list,
- struct fsnotify_event *event)
+static int inotify_merge(struct list_head *list,
+ struct fsnotify_event *event)
{
struct fsnotify_event *last_event;
last_event = list_entry(list->prev, struct fsnotify_event, list);
- if (!event_compare(last_event, event))
- return NULL;
- return last_event;
+ return event_compare(last_event, event);
}
int inotify_handle_event(struct fsnotify_group *group,
@@ -73,9 +71,8 @@
{
struct inotify_inode_mark *i_mark;
struct inotify_event_info *event;
- struct fsnotify_event *added_event;
struct fsnotify_event *fsn_event;
- int ret = 0;
+ int ret;
int len = 0;
int alloc_len = sizeof(struct inotify_event_info);
@@ -110,18 +107,16 @@
if (len)
strcpy(event->name, file_name);
- added_event = fsnotify_add_notify_event(group, fsn_event, inotify_merge);
- if (added_event) {
+ ret = fsnotify_add_notify_event(group, fsn_event, inotify_merge);
+ if (ret) {
/* Our event wasn't used in the end. Free it. */
fsnotify_destroy_event(group, fsn_event);
- if (IS_ERR(added_event))
- ret = PTR_ERR(added_event);
}
if (inode_mark->mask & IN_ONESHOT)
fsnotify_destroy_mark(inode_mark, group);
- return ret;
+ return 0;
}
static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index 952237b..18b3c44 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -79,15 +79,15 @@
/*
* Add an event to the group notification queue. The group can later pull this
- * event off the queue to deal with. If the event is successfully added to the
- * group's notification queue, a reference is taken on event.
+ * 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.
*/
-struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
- struct fsnotify_event *event,
- struct fsnotify_event *(*merge)(struct list_head *,
- struct fsnotify_event *))
+int fsnotify_add_notify_event(struct fsnotify_group *group,
+ struct fsnotify_event *event,
+ int (*merge)(struct list_head *,
+ struct fsnotify_event *))
{
- struct fsnotify_event *return_event = NULL;
+ int ret = 0;
struct list_head *list = &group->notification_list;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
@@ -98,14 +98,14 @@
/* Queue overflow event only if it isn't already queued */
if (list_empty(&group->overflow_event.list))
event = &group->overflow_event;
- return_event = event;
+ ret = 1;
}
if (!list_empty(list) && merge) {
- return_event = merge(list, event);
- if (return_event) {
+ ret = merge(list, event);
+ if (ret) {
mutex_unlock(&group->notification_mutex);
- return return_event;
+ return ret;
}
}
@@ -115,7 +115,7 @@
wake_up(&group->notification_waitq);
kill_fasync(&group->fsn_fa, SIGIO, POLL_IN);
- return return_event;
+ return ret;
}
/*
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 7d8d5e6..3d286ff 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -322,10 +322,10 @@
extern void fsnotify_destroy_event(struct fsnotify_group *group,
struct fsnotify_event *event);
/* attach the event to the group notification queue */
-extern struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group,
- struct fsnotify_event *event,
- struct fsnotify_event *(*merge)(struct list_head *,
- struct fsnotify_event *));
+extern int fsnotify_add_notify_event(struct fsnotify_group *group,
+ struct fsnotify_event *event,
+ int (*merge)(struct list_head *,
+ struct fsnotify_event *));
/* true if the group notification queue is empty */
extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
/* return, but do not dequeue the first event on the notification queue */