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

[Christian Brauner]

On Fri, Jan 31, 2025 at 11:53:33AM +0100, Miklos Szeredi wrote:
> On Thu, 30 Jan 2025 at 22:06, Paul Moore <paul at paul-moore.com> wrote:
> >
> > On Wed, Jan 29, 2025 at 11:58 AM Miklos Szeredi <mszeredi at redhat.com> wrote:
> > >
> > > Add notifications for attaching and detaching mounts.  The following new
> > > event masks are added:
> > >
> > >   FAN_MNT_ATTACH  - Mount was attached
> > >   FAN_MNT_DETACH  - Mount was detached
> > >
> > > If a mount is moved, then the event is reported with (FAN_MNT_ATTACH |
> > > FAN_MNT_DETACH).
> > >
> > > These events add an info record of type FAN_EVENT_INFO_TYPE_MNT containing
> > > these fields identifying the affected mounts:
> > >
> > >   __u64 mnt_id    - the ID of the mount (see statmount(2))
> > >
> > > FAN_REPORT_MNT must be supplied to fanotify_init() to receive these events
> > > and no other type of event can be received with this report type.
> > >
> > > Marks are added with FAN_MARK_MNTNS, which records the mount namespace from
> > > an nsfs file (e.g. /proc/self/ns/mnt).
> > >
> > > Signed-off-by: Miklos Szeredi <mszeredi at redhat.com>
> > > ---
> > >  fs/mount.h                         |  2 +
> > >  fs/namespace.c                     | 14 +++--
> > >  fs/notify/fanotify/fanotify.c      | 38 +++++++++++--
> > >  fs/notify/fanotify/fanotify.h      | 18 +++++++
> > >  fs/notify/fanotify/fanotify_user.c | 87 +++++++++++++++++++++++++-----
> > >  fs/notify/fdinfo.c                 |  5 ++
> > >  include/linux/fanotify.h           | 12 +++--
> > >  include/uapi/linux/fanotify.h      | 10 ++++
> > >  security/selinux/hooks.c           |  4 ++
> > >  9 files changed, 167 insertions(+), 23 deletions(-)
> >
> > ...
> >
> > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> > > index 7b867dfec88b..06d073eab53c 100644
> > > --- a/security/selinux/hooks.c
> > > +++ b/security/selinux/hooks.c
> > > @@ -3395,6 +3395,10 @@ static int selinux_path_notify(const struct path *path, u64 mask,
> > >         case FSNOTIFY_OBJ_TYPE_INODE:
> > >                 perm = FILE__WATCH;
> > >                 break;
> > > +       case FSNOTIFY_OBJ_TYPE_MNTNS:
> > > +               /* Maybe introduce FILE__WATCH_MOUNTNS? */
> > > +               perm = FILE__WATCH_MOUNT;
> > > +               break;
> > >         default:
> > >                 return -EINVAL;
> > >         }
> >
> > Ignoring for a moment that this patch was merged without an explicit
> > ACK for the SELinux changes, let's talk about these SELinux changes
> > ...
> >
> > I understand that you went with the "simpler version" because you
> > didn't believe the discussion was converging, which is fair, however,
> > I believe Daniel's argument is convincing enough to warrant the new
> > permission.
> 
> Fine, I'll work on this.

Make it separate patches please. All LSM changes have been dropped.