fanotify: create overflow event type

The special overflow event is allocated as struct fanotify_path_event,
but with a null path.

Use a special event type to identify the overflow event, so the helper
fanotify_has_event_path() will always indicate a non null path.

Allocating the overflow event doesn't need any of the fancy stuff in
fanotify_alloc_event(), so create a simplified helper for allocating the
overflow event.

There is also no need to store and report the pid with an overflow event.

Link: https://lore.kernel.org/r/20200708111156.24659-7-amir73il@gmail.com
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 9 insertions, 6 deletions

diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 8ce7ccfc4b0d..1b2a3bbe6008 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -63,6 +63,7 @@ enum fanotify_event_type {
 	FANOTIFY_EVENT_TYPE_FID_NAME, /* variable length */
 	FANOTIFY_EVENT_TYPE_PATH,
 	FANOTIFY_EVENT_TYPE_PATH_PERM,
+	FANOTIFY_EVENT_TYPE_OVERFLOW, /* struct fanotify_event */
 };
 
 struct fanotify_event {
@@ -72,6 +73,14 @@ struct fanotify_event {
 	struct pid *pid;
 };
 
+static inline void fanotify_init_event(struct fanotify_event *event,
+				       unsigned long id, u32 mask)
+{
+	fsnotify_init_event(&event->fse, id);
+	event->mask = mask;
+	event->pid = NULL;
+}
+
 struct fanotify_fid_event {
 	struct fanotify_event fae;
 	__kernel_fsid_t fsid;
@@ -202,9 +211,3 @@ static inline struct path *fanotify_event_path(struct fanotify_event *event)
 	else
 		return NULL;
 }
-
-struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
-					    struct inode *inode, u32 mask,
-					    const void *data, int data_type,
-					    const struct qstr *file_name,
-					    __kernel_fsid_t *fsid);