[PATCH 6/7] fanotify: report new parent and name in MOVED_FROM event

[Amir Goldstein <amir73il@gmail.com>]

In the special case of MOVED_FROM event, if we are reporting the child
fid due to FAN_REPORT_TARGET_FID init flag, we also report the new
parent and name.

The new parent and name are reported using a new info record of type
FAN_EVENT_INFO_TYPE_DFID_NAME2 that follows the info record of type
FAN_EVENT_INFO_TYPE_DFID_NAME with the old parent and name.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify.h      | 17 +++++++++++++++++
 fs/notify/fanotify/fanotify_user.c | 29 +++++++++++++++++++++++++++--
 include/uapi/linux/fanotify.h      |  1 +
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 0864e7efe23c..26d471aab054 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -339,6 +339,13 @@ static inline int fanotify_event_dir_fh_len(struct fanotify_event *event)
 	return info ? fanotify_info_dir_fh_len(info) : 0;
 }
 
+static inline int fanotify_event_dir2_fh_len(struct fanotify_event *event)
+{
+	struct fanotify_info *info = fanotify_event_info(event);
+
+	return info ? fanotify_info_dir2_fh_len(info) : 0;
+}
+
 static inline bool fanotify_event_has_object_fh(struct fanotify_event *event)
 {
 	/* For error events, even zeroed fh are reported. */
@@ -352,6 +359,16 @@ static inline bool fanotify_event_has_dir_fh(struct fanotify_event *event)
 	return fanotify_event_dir_fh_len(event) > 0;
 }
 
+/* For MOVED_FROM event with FAN_REPORT_TARGET_FID */
+static inline bool fanotify_event_has_two_names(struct fanotify_event *event)
+{
+	struct fanotify_info *info = fanotify_event_info(event);
+
+	return info && info->name_len && info->name2_len &&
+		fanotify_info_dir_fh_len(info) > 0 &&
+		fanotify_info_dir2_fh_len(info) > 0;
+}
+
 struct fanotify_path_event {
 	struct fanotify_event fae;
 	struct path path;
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index d973f36676a9..d6420e10740d 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -134,7 +134,7 @@ static size_t fanotify_event_len(unsigned int info_mode,
 {
 	size_t event_len = FAN_EVENT_METADATA_LEN;
 	struct fanotify_info *info;
-	int dir_fh_len;
+	int dir_fh_len, dir2_fh_len;
 	int fh_len;
 	int dot_len = 0;
 
@@ -149,6 +149,11 @@ static size_t fanotify_event_len(unsigned int info_mode,
 	if (fanotify_event_has_dir_fh(event)) {
 		dir_fh_len = fanotify_event_dir_fh_len(event);
 		event_len += fanotify_fid_info_len(dir_fh_len, info->name_len);
+		if (fanotify_event_has_two_names(event)) {
+			dir2_fh_len = fanotify_event_dir2_fh_len(event);
+			event_len += fanotify_fid_info_len(dir2_fh_len,
+							   info->name2_len);
+		}
 	} else if ((info_mode & FAN_REPORT_NAME) &&
 		   (event->mask & FAN_ONDIR)) {
 		/*
@@ -379,6 +384,7 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
 			return -EFAULT;
 		break;
 	case FAN_EVENT_INFO_TYPE_DFID_NAME:
+	case FAN_EVENT_INFO_TYPE_DFID_NAME2:
 		if (WARN_ON_ONCE(!name || !name_len))
 			return -EFAULT;
 		break;
@@ -478,7 +484,10 @@ static int copy_info_records_to_user(struct fanotify_event *event,
 	unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
 
 	/*
-	 * Event info records order is as follows: dir fid + name, child fid.
+	 * Event info records order is as follows:
+	 * 1. dir fid + name
+	 * 2. (optional) new dir fid + new name
+	 * 3. (optional) child fid
 	 */
 	if (fanotify_event_has_dir_fh(event)) {
 		info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
@@ -496,6 +505,22 @@ static int copy_info_records_to_user(struct fanotify_event *event,
 		total_bytes += ret;
 	}
 
+	/* New dir fid + name can only be reported after old dir fid + name */
+	if (info_type && fanotify_event_has_two_names(event)) {
+		info_type = FAN_EVENT_INFO_TYPE_DFID_NAME2;
+		ret = copy_fid_info_to_user(fanotify_event_fsid(event),
+					    fanotify_info_dir2_fh(info),
+					    info_type,
+					    fanotify_info_name2(info),
+					    info->name2_len, buf, count);
+		if (ret < 0)
+			return ret;
+
+		buf += ret;
+		count -= ret;
+		total_bytes += ret;
+	}
+
 	if (fanotify_event_has_object_fh(event)) {
 		const char *dot = NULL;
 		int dot_len = 0;
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index f9202ce31b0d..1ac31a912cea 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -131,6 +131,7 @@ struct fanotify_event_metadata {
 #define FAN_EVENT_INFO_TYPE_DFID	3
 #define FAN_EVENT_INFO_TYPE_PIDFD	4
 #define FAN_EVENT_INFO_TYPE_ERROR	5
+#define FAN_EVENT_INFO_TYPE_DFID_NAME2	6 /* For FAN_MOVED_FROM */
 
 /* Variable length info record following event metadata */
 struct fanotify_event_info_header {
-- 
2.33.1