[PATCH v5 2/3] fanotify: notify on mount attach and detach

[Miklos Szeredi]

On Tue, 11 Feb 2025 at 16:50, Jan Kara <jack at suse.cz> wrote:
>
> On Wed 29-01-25 17:58:00, Miklos Szeredi wrote:

> >       fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
> > -     if (mask & ~(FANOTIFY_FD_EVENTS|FANOTIFY_EVENT_FLAGS) &&
> > +     if (mask & ~(FANOTIFY_FD_EVENTS|FANOTIFY_MOUNT_EVENTS|FANOTIFY_EVENT_FLAGS) &&
>
> I understand why you need this but the condition is really hard to
> understand now and the comment above it becomes out of date. Perhaps I'd
> move this and the following two checks for FAN_RENAME and
> FANOTIFY_PRE_CONTENT_EVENTS into !FAN_GROUP_FLAG(group, FAN_REPORT_MNT)
> branch to make things more obvious?

Okay.  git diff -w below.

Thanks,
Miklos

--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1936,6 +1936,8 @@ static int do_fanotify_mark(int fanotify_fd,
unsigned int flags, __u64 mask,
             mark_type != FAN_MARK_INODE)
                return -EINVAL;

+       /* The following checks are not relevant to mount events */
+       if (!FAN_GROUP_FLAG(group, FAN_REPORT_MNT)) {
                /*
                 * Events that do not carry enough information to report
                 * event->fd require a group that supports reporting fid.  Those
@@ -1944,21 +1946,25 @@ static int do_fanotify_mark(int fanotify_fd,
unsigned int flags, __u64 mask,
                 * point.
                 */
                fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
-       if (mask &
~(FANOTIFY_FD_EVENTS|FANOTIFY_MOUNT_EVENTS|FANOTIFY_EVENT_FLAGS) &&
+               if (mask & ~(FANOTIFY_FD_EVENTS|FANOTIFY_EVENT_FLAGS) &&
                    (!fid_mode || mark_type == FAN_MARK_MOUNT))
                        return -EINVAL;

                /*
-        * FAN_RENAME uses special info type records to report the old and
-        * new parent+name.  Reporting only old and new parent id is less
-        * useful and was not implemented.
+                * FAN_RENAME uses special info type records to report the old
+                * and new parent+name.  Reporting only old and new parent id is
+                * less useful and was not implemented.
                 */
                if (mask & FAN_RENAME && !(fid_mode & FAN_REPORT_NAME))
                        return -EINVAL;

-       /* Pre-content events are not currently generated for directories. */
+               /*
+                * Pre-content events are not currently generated for
+                * directories.
+                */
                if (mask & FANOTIFY_PRE_CONTENT_EVENTS && mask & FAN_ONDIR)
                        return -EINVAL;
+       }

        if (mark_cmd == FAN_MARK_FLUSH) {
                if (mark_type == FAN_MARK_MOUNT)