fanotify: report old and/or new parent+name in FAN_RENAME event

In the special case of FAN_RENAME event, we report old or new or both
old and new parent+name.

A single info record will be reported if either the old or new dir
is watched and two records will be reported if both old and new dir
(or their filesystem) are watched.

The old and new parent+name are reported using new info record types
FAN_EVENT_INFO_TYPE_{OLD,NEW}_DFID_NAME, so if a single info record
is reported, it is clear to the application, to which dir entry the
fid+name info is referring to.

Link: https://lore.kernel.org/r/20211129201537.1932819-11-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 47 insertions, 5 deletions

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index e4a11f56782d..eb2a0251b318 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -129,12 +129,29 @@ static int fanotify_fid_info_len(int fh_len, int name_len)
 		       FANOTIFY_EVENT_ALIGN);
 }
 
+/* FAN_RENAME may have one or two dir+name info records */
+static int fanotify_dir_name_info_len(struct fanotify_event *event)
+{
+	struct fanotify_info *info = fanotify_event_info(event);
+	int dir_fh_len = fanotify_event_dir_fh_len(event);
+	int dir2_fh_len = fanotify_event_dir2_fh_len(event);
+	int info_len = 0;
+
+	if (dir_fh_len)
+		info_len += fanotify_fid_info_len(dir_fh_len,
+						  info->name_len);
+	if (dir2_fh_len)
+		info_len += fanotify_fid_info_len(dir2_fh_len,
+						  info->name2_len);
+
+	return info_len;
+}
+
 static size_t fanotify_event_len(unsigned int info_mode,
 				 struct fanotify_event *event)
 {
 	size_t event_len = FAN_EVENT_METADATA_LEN;
 	struct fanotify_info *info;
-	int dir_fh_len;
 	int fh_len;
 	int dot_len = 0;
 
@@ -146,9 +163,8 @@ static size_t fanotify_event_len(unsigned int info_mode,
 
 	info = fanotify_event_info(event);
 
-	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_any_dir_fh(event)) {
+		event_len += fanotify_dir_name_info_len(event);
 	} else if ((info_mode & FAN_REPORT_NAME) &&
 		   (event->mask & FAN_ONDIR)) {
 		/*
@@ -379,6 +395,8 @@ 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_OLD_DFID_NAME:
+	case FAN_EVENT_INFO_TYPE_NEW_DFID_NAME:
 		if (WARN_ON_ONCE(!name || !name_len))
 			return -EFAULT;
 		break;
@@ -478,11 +496,19 @@ 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 :
 					     FAN_EVENT_INFO_TYPE_DFID;
+
+		/* FAN_RENAME uses special info types */
+		if (event->mask & FAN_RENAME)
+			info_type = FAN_EVENT_INFO_TYPE_OLD_DFID_NAME;
+
 		ret = copy_fid_info_to_user(fanotify_event_fsid(event),
 					    fanotify_info_dir_fh(info),
 					    info_type,
@@ -496,6 +522,22 @@ static int copy_info_records_to_user(struct fanotify_event *event,
 		total_bytes += ret;
 	}
 
+	/* New dir fid+name may be reported in addition to old dir fid+name */
+	if (fanotify_event_has_dir2_fh(event)) {
+		info_type = FAN_EVENT_INFO_TYPE_NEW_DFID_NAME;
+		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;