[RFC][PATCH 2/6] fanotify: report events to sb root with fanotify_file_event_info

[Amir Goldstein <amir73il@gmail.com>]

Allocate variable length fanotify_file_event_info struct to
report events when FAN_EVENT_ON_SB mask is set on event.

This is needed to provide extra info on the event for the
super block watcher.

An exception is made for permission event which use the
fanotify_perm_event_info struct also when reporting to
super block watcher.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify.c      | 19 +++++++++++++------
 fs/notify/fanotify/fanotify.h      | 21 +++++++++++++++++++++
 fs/notify/fanotify/fanotify_user.c |  8 ++++----
 3 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 67feeb6..8a88d88 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -41,7 +41,7 @@ static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
 	 * the event structure we have created in fanotify_handle_event() is the
 	 * one we should check for permission response.
 	 */
-	if (event->mask & FAN_ALL_PERM_EVENTS)
+	if (FANOTIFY_IS_PE(event))
 		return 0;
 #endif
 
@@ -169,11 +169,18 @@ struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
 #endif
 
 	/*
-	 * For filename events (create,delete,rename), path points to the
+	 * For filename events (create,delete,move), path points to the
 	 * directory and name holds the entry name, so allocate a variable
 	 * length fanotify_file_event_info struct.
+	 *
+	 * When non permission events are reported on super block root watch,
+	 * they may need to carry extra file information. So alway allocate
+	 * fanotify_file_event_info struct for those events, even if data len
+	 * end up being 0.
+	 * This makes it easier to know when an event struct should be cast
+	 * to FANOTIFY_FE(), e.g. in fanotify_free_event().
 	 */
-	if (mask & FAN_FILENAME_EVENTS) {
+	if (mask & (FAN_FILENAME_EVENTS | FAN_EVENT_ON_SB)) {
 		struct fanotify_file_event_info *ffe;
 		int alloc_len = sizeof(*ffe);
 		int len = 0;
@@ -276,7 +283,7 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	}
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	if (mask & FAN_ALL_PERM_EVENTS) {
+	if (FANOTIFY_IS_PE(fsn_event)) {
 		ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event));
 		fsnotify_destroy_event(group, fsn_event);
 	}
@@ -301,13 +308,13 @@ static void fanotify_free_event(struct fsnotify_event *fsn_event)
 	path_put(&event->path);
 	put_pid(event->tgid);
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
+	if (FANOTIFY_IS_PE(fsn_event)) {
 		kmem_cache_free(fanotify_perm_event_cachep,
 				FANOTIFY_PE(fsn_event));
 		return;
 	}
 #endif
-	if (fsn_event->mask & FAN_FILENAME_EVENTS) {
+	if (FANOTIFY_IS_FE(fsn_event)) {
 		kfree(FANOTIFY_FE(fsn_event));
 		return;
 	}
diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index d0bb7acb4..d23b35b 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -54,8 +54,29 @@ FANOTIFY_PE(struct fsnotify_event *fse)
 {
 	return container_of(fse, struct fanotify_perm_event_info, fae.fse);
 }
+
+/* Should use fanotify_perm_event_info for this event? */
+static inline bool FANOTIFY_IS_PE(struct fsnotify_event *fse)
+{
+	return fse->mask & FAN_ALL_PERM_EVENTS;
+}
+#else
+static inline bool FANOTIFY_IS_PE(struct fsnotify_event *fse)
+{
+	return false;
+}
 #endif
 
+/* Should use fanotify_file_event_info for this event? */
+static inline bool FANOTIFY_IS_FE(struct fsnotify_event *fse)
+{
+	if (FANOTIFY_IS_PE(fse))
+		return false;
+
+	/* Non permission events reported on root may carry file info */
+	return fse->mask & (FAN_FILENAME_EVENTS | FAN_EVENT_ON_SB);
+}
+
 static inline struct fanotify_file_event_info *
 FANOTIFY_FE(struct fsnotify_event *fse)
 {
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index e57c82a..191bd7d 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -229,7 +229,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 	if (ret < 0)
 		return ret;
 
-	if ((event->mask & FAN_FILENAME_EVENTS) &&
+	if (FANOTIFY_IS_FE(event) &&
 	    (group->fanotify_data.flags & FAN_EVENT_INFO_NAME)) {
 		ffe = FANOTIFY_FE(event);
 		pad_name_len = round_event_name_len(ffe);
@@ -261,7 +261,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 	}
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-	if (event->mask & FAN_ALL_PERM_EVENTS)
+	if (FANOTIFY_IS_PE(event))
 		FANOTIFY_PE(event)->fd = fd;
 #endif
 
@@ -338,7 +338,7 @@ static ssize_t fanotify_read(struct file *file, char __user *buf,
 		 * Permission events get queued to wait for response.  Other
 		 * events can be destroyed now.
 		 */
-		if (!(kevent->mask & FAN_ALL_PERM_EVENTS)) {
+		if (!FANOTIFY_IS_PE(kevent)) {
 			fsnotify_destroy_event(group, kevent);
 			if (ret < 0)
 				break;
@@ -428,7 +428,7 @@ static int fanotify_release(struct inode *ignored, struct file *file)
 	 */
 	while (!fsnotify_notify_queue_is_empty(group)) {
 		fsn_event = fsnotify_remove_first_event(group);
-		if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) {
+		if (!FANOTIFY_IS_PE(fsn_event)) {
 			spin_unlock(&group->notification_lock);
 			fsnotify_destroy_event(group, fsn_event);
 			spin_lock(&group->notification_lock);
-- 
2.7.4