fanotify: notify on mount attach and detach

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
belonging to the supplied path.

Prior to this patch mount namespace changes could be monitored by polling
/proc/self/mountinfo, which did not convey any information about what
changed.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---

v3:

  - use a global list protected for temporarily storing (Christian)
  - move fsnotify_* calls to namespace_unlock() (Christian)
  - downgrade namespace_sem to read for fsnotify_* calls (Christian)
  - add notification for reparenting in propagate_umount (Christian)
  - require nsfs file (/proc/PID/ns/mnt) in fanotify_mark(2) (Christian)
  - cleaner check for fsnotify being initialized (Amir)
  - fix stub __fsnotify_mntns_delete (kernel test robot)
  - don't add FANOTIFY_MOUNT_EVENTS to FANOTIFY_FD_EVENTS (Amir)

v2:
  - notify for whole namespace as this seems to be what people prefer
  - move fsnotify() calls outside of mount_lock
  - only report mnt_id, not parent_id

 fs/mount.h                         | 21 ++++++++++
 fs/namespace.c                     | 62 ++++++++++++++++++++++++++---
 fs/notify/fanotify/fanotify.c      | 37 +++++++++++++++--
 fs/notify/fanotify/fanotify.h      | 18 +++++++++
 fs/notify/fanotify/fanotify_user.c | 64 ++++++++++++++++++++++++++++--
 fs/notify/fdinfo.c                 |  2 +
 fs/notify/fsnotify.c               | 47 ++++++++++++++++++----
 fs/notify/fsnotify.h               | 11 +++++
 fs/notify/mark.c                   | 14 +++++--
 fs/pnode.c                         |  4 +-
 include/linux/fanotify.h           | 12 ++++--
 include/linux/fsnotify.h           | 20 ++++++++++
 include/linux/fsnotify_backend.h   | 40 ++++++++++++++++++-
 include/linux/mnt_namespace.h      |  1 +
 include/uapi/linux/fanotify.h      | 10 +++++
 security/selinux/hooks.c           |  4 ++
 16 files changed, 340 insertions(+), 27 deletions(-)

diff --git a/fs/mount.h b/fs/mount.h
index 185fc56afc13..0ad68c90e7e2 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -5,6 +5,8 @@
 #include <linux/ns_common.h>
 #include <linux/fs_pin.h>
 
+extern struct list_head notify_list;
+
 struct mnt_namespace {
 	struct ns_common	ns;
 	struct mount *	root;
@@ -14,6 +16,10 @@ struct mnt_namespace {
 	u64			seq;	/* Sequence number to prevent loops */
 	wait_queue_head_t poll;
 	u64 event;
+#ifdef CONFIG_FSNOTIFY
+	__u32			n_fsnotify_mask;
+	struct fsnotify_mark_connector __rcu *n_fsnotify_marks;
+#endif
 	unsigned int		nr_mounts; /* # of mounts in the namespace */
 	unsigned int		pending_mounts;
 	struct rb_node		mnt_ns_tree_node; /* node in the mnt_ns_tree */
@@ -77,6 +83,9 @@ struct mount {
 	int mnt_expiry_mark;		/* true if marked for expiry */
 	struct hlist_head mnt_pins;
 	struct hlist_head mnt_stuck_children;
+
+	struct list_head to_notify;	/* need to queue notification */
+	struct mnt_namespace *prev_ns;	/* previous namespace (NULL if none) */
 } __randomize_layout;
 
 #define MNT_NS_INTERNAL ERR_PTR(-EINVAL) /* distinct from any mnt_namespace */
@@ -167,3 +176,15 @@ static inline struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
 {
 	return container_of(ns, struct mnt_namespace, ns);
 }
+
+static inline void add_notify(struct mount *m)
+{
+	/* Optimize the case where there are no watches */
+	if ((m->mnt_ns && m->mnt_ns->n_fsnotify_marks) ||
+	    (m->prev_ns && m->prev_ns->n_fsnotify_marks))
+		list_add_tail(&m->to_notify, &notify_list);
+	else
+		m->prev_ns = m->mnt_ns;
+}
+
+struct mnt_namespace *mnt_ns_from_dentry(struct dentry *dentry);
diff --git a/fs/namespace.c b/fs/namespace.c
index 6eec7794f707..186f660abd60 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -79,6 +79,7 @@ static struct kmem_cache *mnt_cache __ro_after_init;
 static DECLARE_RWSEM(namespace_sem);
 static HLIST_HEAD(unmounted);	/* protected by namespace_sem */
 static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
+LIST_HEAD(notify_list); /* protected by namespace_sem */
 static DEFINE_RWLOCK(mnt_ns_tree_lock);
 static struct rb_root mnt_ns_tree = RB_ROOT; /* protected by mnt_ns_tree_lock */
 
@@ -145,6 +146,7 @@ static void mnt_ns_release(struct mnt_namespace *ns)
 
 	/* keep alive for {list,stat}mount() */
 	if (refcount_dec_and_test(&ns->passive)) {
+		fsnotify_mntns_delete(ns);
 		put_user_ns(ns->user_ns);
 		kfree(ns);
 	}
@@ -1136,6 +1138,8 @@ static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt)
 	rb_link_node(&mnt->mnt_node, parent, link);
 	rb_insert_color(&mnt->mnt_node, &ns->mounts);
 	mnt->mnt.mnt_flags |= MNT_ONRB;
+
+	add_notify(mnt);
 }
 
 /*
@@ -1683,17 +1687,53 @@ int may_umount(struct vfsmount *mnt)
 
 EXPORT_SYMBOL(may_umount);
 
+static void notify_mount(struct mount *p)
+{
+	if (!p->prev_ns && p->mnt_ns) {
+		fsnotify_mnt_attach(p->mnt_ns, &p->mnt);
+	} else if (p->prev_ns && !p->mnt_ns) {
+		fsnotify_mnt_detach(p->prev_ns, &p->mnt);
+	} else if (p->prev_ns == p->mnt_ns) {
+		fsnotify_mnt_move(p->mnt_ns, &p->mnt);
+	} else {
+		fsnotify_mnt_detach(p->prev_ns, &p->mnt);
+		fsnotify_mnt_attach(p->mnt_ns, &p->mnt);
+	}
+	p->prev_ns = p->mnt_ns;
+}
+
 static void namespace_unlock(void)
 {
 	struct hlist_head head;
 	struct hlist_node *p;
-	struct mount *m;
+	struct mount *m, *tmp;
 	LIST_HEAD(list);
+	bool notify = !list_empty(&notify_list);
 
 	hlist_move_list(&unmounted, &head);
 	list_splice_init(&ex_mountpoints, &list);
 
-	up_write(&namespace_sem);
+	/*
+	 * No point blocking out concurrent readers while notifications are
+	 * sent. This will also allow statmount()/listmount() to run
+	 * concurrently.
+	 */
+	if (unlikely(notify))
+		downgrade_write(&namespace_sem);
+
+	/*
+	 * Notify about mounts that were added/reparented/remain connected after
+	 * unmount.
+	 */
+	list_for_each_entry_safe(m, tmp, &notify_list, to_notify) {
+		notify_mount(m);
+		list_del_init(&m->to_notify);
+	}
+
+	if (unlikely(notify))
+		up_read(&namespace_sem);
+	else
+		up_write(&namespace_sem);
 
 	shrink_dentry_list(&list);
 
@@ -1806,6 +1846,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
 		change_mnt_propagation(p, MS_PRIVATE);
 		if (disconnect)
 			hlist_add_head(&p->mnt_umount, &unmounted);
+		add_notify(p);
 	}
 }
 
@@ -2103,16 +2144,24 @@ struct mnt_namespace *__lookup_next_mnt_ns(struct mnt_namespace *mntns, bool pre
 	}
 }
 
+struct mnt_namespace *mnt_ns_from_dentry(struct dentry *dentry)
+{
+	if (!is_mnt_ns_file(dentry))
+		return NULL;
+
+	return to_mnt_ns(get_proc_ns(dentry->d_inode));
+}
+
 static bool mnt_ns_loop(struct dentry *dentry)
 {
 	/* Could bind mounting the mount namespace inode cause a
 	 * mount namespace loop?
 	 */
-	struct mnt_namespace *mnt_ns;
-	if (!is_mnt_ns_file(dentry))
+	struct mnt_namespace *mnt_ns = mnt_ns_from_dentry(dentry);
+
+	if (!mnt_ns)
 		return false;
 
-	mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
 	return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
 }
 
@@ -2505,6 +2554,7 @@ static int attach_recursive_mnt(struct mount *source_mnt,
 			dest_mp = smp;
 		unhash_mnt(source_mnt);
 		attach_mnt(source_mnt, top_mnt, dest_mp, beneath);
+		add_notify(source_mnt);
 		touch_mnt_namespace(source_mnt->mnt_ns);
 	} else {
 		if (source_mnt->mnt_ns) {
@@ -4420,6 +4470,8 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
 	list_del_init(&new_mnt->mnt_expire);
 	put_mountpoint(root_mp);
 	unlock_mount_hash();
+	add_notify(root_mnt);
+	add_notify(new_mnt);
 	chroot_fs_refs(&root, &new);
 	error = 0;
 out4:
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 24c7c5df4998..a9dc004291bf 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -166,6 +166,8 @@ static bool fanotify_should_merge(struct fanotify_event *old,
 	case FANOTIFY_EVENT_TYPE_FS_ERROR:
 		return fanotify_error_event_equal(FANOTIFY_EE(old),
 						  FANOTIFY_EE(new));
+	case FANOTIFY_EVENT_TYPE_MNT:
+		return false;
 	default:
 		WARN_ON_ONCE(1);
 	}
@@ -303,7 +305,11 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 	pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
 		 __func__, iter_info->report_mask, event_mask, data, data_type);
 
-	if (!fid_mode) {
+	if (FAN_GROUP_FLAG(group, FAN_REPORT_MNT))
+	{
+		if (data_type != FSNOTIFY_EVENT_MNT)
+			return 0;
+	} else if (!fid_mode) {
 		/* Do we have path to open a file descriptor? */
 		if (!path)
 			return 0;
@@ -548,6 +554,20 @@ static struct fanotify_event *fanotify_alloc_path_event(const struct path *path,
 	return &pevent->fae;
 }
 
+static struct fanotify_event *fanotify_alloc_mnt_event(u64 mnt_id, gfp_t gfp)
+{
+	struct fanotify_mnt_event *pevent;
+
+	pevent = kmem_cache_alloc(fanotify_mnt_event_cachep, gfp);
+	if (!pevent)
+		return NULL;
+
+	pevent->fae.type = FANOTIFY_EVENT_TYPE_MNT;
+	pevent->mnt_id = mnt_id;
+
+	return &pevent->fae;
+}
+
 static struct fanotify_event *fanotify_alloc_perm_event(const struct path *path,
 							gfp_t gfp)
 {
@@ -715,6 +735,7 @@ static struct fanotify_event *fanotify_alloc_event(
 					      fid_mode);
 	struct inode *dirid = fanotify_dfid_inode(mask, data, data_type, dir);
 	const struct path *path = fsnotify_data_path(data, data_type);
+	u64 mnt_id = fsnotify_data_mnt_id(data, data_type);
 	struct mem_cgroup *old_memcg;
 	struct dentry *moved = NULL;
 	struct inode *child = NULL;
@@ -810,8 +831,10 @@ static struct fanotify_event *fanotify_alloc_event(
 						  moved, &hash, gfp);
 	} else if (fid_mode) {
 		event = fanotify_alloc_fid_event(id, fsid, &hash, gfp);
-	} else {
+	} else if (path) {
 		event = fanotify_alloc_path_event(path, &hash, gfp);
+	} else /* if (mnt_id) */ {
+		event = fanotify_alloc_mnt_event(mnt_id, gfp);
 	}
 
 	if (!event)
@@ -910,7 +933,7 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
 	BUILD_BUG_ON(FAN_FS_ERROR != FS_ERROR);
 	BUILD_BUG_ON(FAN_RENAME != FS_RENAME);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 21);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 23);
 
 	mask = fanotify_group_event_mask(group, iter_info, &match_mask,
 					 mask, data, data_type, dir);
@@ -1011,6 +1034,11 @@ static void fanotify_free_error_event(struct fsnotify_group *group,
 	mempool_free(fee, &group->fanotify_data.error_events_pool);
 }
 
+static void fanotify_free_mnt_event(struct fanotify_event *event)
+{
+	kmem_cache_free(fanotify_mnt_event_cachep, FANOTIFY_ME(event));
+}
+
 static void fanotify_free_event(struct fsnotify_group *group,
 				struct fsnotify_event *fsn_event)
 {
@@ -1037,6 +1065,9 @@ static void fanotify_free_event(struct fsnotify_group *group,
 	case FANOTIFY_EVENT_TYPE_FS_ERROR:
 		fanotify_free_error_event(group, event);
 		break;
+	case FANOTIFY_EVENT_TYPE_MNT:
+		fanotify_free_mnt_event(event);
+		break;
 	default:
 		WARN_ON_ONCE(1);
 	}
diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index e5ab33cae6a7..f1a7cbedc9e3 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -9,6 +9,7 @@ extern struct kmem_cache *fanotify_mark_cache;
 extern struct kmem_cache *fanotify_fid_event_cachep;
 extern struct kmem_cache *fanotify_path_event_cachep;
 extern struct kmem_cache *fanotify_perm_event_cachep;
+extern struct kmem_cache *fanotify_mnt_event_cachep;
 
 /* Possible states of the permission event */
 enum {
@@ -244,6 +245,7 @@ enum fanotify_event_type {
 	FANOTIFY_EVENT_TYPE_PATH_PERM,
 	FANOTIFY_EVENT_TYPE_OVERFLOW, /* struct fanotify_event */
 	FANOTIFY_EVENT_TYPE_FS_ERROR, /* struct fanotify_error_event */
+	FANOTIFY_EVENT_TYPE_MNT,
 	__FANOTIFY_EVENT_TYPE_NUM
 };
 
@@ -409,12 +411,23 @@ struct fanotify_path_event {
 	struct path path;
 };
 
+struct fanotify_mnt_event {
+	struct fanotify_event fae;
+	u64 mnt_id;
+};
+
 static inline struct fanotify_path_event *
 FANOTIFY_PE(struct fanotify_event *event)
 {
 	return container_of(event, struct fanotify_path_event, fae);
 }
 
+static inline struct fanotify_mnt_event *
+FANOTIFY_ME(struct fanotify_event *event)
+{
+	return container_of(event, struct fanotify_mnt_event, fae);
+}
+
 /*
  * Structure for permission fanotify events. It gets allocated and freed in
  * fanotify_handle_event() since we wait there for user response. When the
@@ -456,6 +469,11 @@ static inline bool fanotify_is_error_event(u32 mask)
 	return mask & FAN_FS_ERROR;
 }
 
+static inline bool fanotify_is_mnt_event(u32 mask)
+{
+	return mask & (FAN_MNT_ATTACH | FAN_MNT_DETACH);
+}
+
 static inline const struct path *fanotify_event_path(struct fanotify_event *event)
 {
 	if (event->type == FANOTIFY_EVENT_TYPE_PATH)
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 2d85c71717d6..1e111730b6bf 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -19,6 +19,7 @@
 #include <linux/memcontrol.h>
 #include <linux/statfs.h>
 #include <linux/exportfs.h>
+#include <linux/mnt_namespace.h>
 
 #include <asm/ioctls.h>
 
@@ -114,6 +115,7 @@ struct kmem_cache *fanotify_mark_cache __ro_after_init;
 struct kmem_cache *fanotify_fid_event_cachep __ro_after_init;
 struct kmem_cache *fanotify_path_event_cachep __ro_after_init;
 struct kmem_cache *fanotify_perm_event_cachep __ro_after_init;
+struct kmem_cache *fanotify_mnt_event_cachep __ro_after_init;
 
 #define FANOTIFY_EVENT_ALIGN 4
 #define FANOTIFY_FID_INFO_HDR_LEN \
@@ -122,6 +124,8 @@ struct kmem_cache *fanotify_perm_event_cachep __ro_after_init;
 	sizeof(struct fanotify_event_info_pidfd)
 #define FANOTIFY_ERROR_INFO_LEN \
 	(sizeof(struct fanotify_event_info_error))
+#define FANOTIFY_MNT_INFO_LEN \
+	(sizeof(struct fanotify_event_info_mnt))
 
 static int fanotify_fid_info_len(int fh_len, int name_len)
 {
@@ -183,6 +187,8 @@ static size_t fanotify_event_len(unsigned int info_mode,
 		fh_len = fanotify_event_object_fh_len(event);
 		event_len += fanotify_fid_info_len(fh_len, dot_len);
 	}
+	if (fanotify_is_mnt_event(event->mask))
+		event_len += FANOTIFY_MNT_INFO_LEN;
 
 	return event_len;
 }
@@ -380,6 +386,25 @@ static int process_access_response(struct fsnotify_group *group,
 	return -ENOENT;
 }
 
+static size_t copy_mnt_info_to_user(struct fanotify_event *event,
+				    char __user *buf, int count)
+{
+	struct fanotify_event_info_mnt info = { };
+
+	info.hdr.info_type = FAN_EVENT_INFO_TYPE_MNT;
+	info.hdr.len = FANOTIFY_MNT_INFO_LEN;
+
+	if (WARN_ON(count < info.hdr.len))
+		return -EFAULT;
+
+	info.mnt_id = FANOTIFY_ME(event)->mnt_id;
+
+	if (copy_to_user(buf, &info, sizeof(info)))
+		return -EFAULT;
+
+	return info.hdr.len;
+}
+
 static size_t copy_error_info_to_user(struct fanotify_event *event,
 				      char __user *buf, int count)
 {
@@ -642,6 +667,14 @@ static int copy_info_records_to_user(struct fanotify_event *event,
 		total_bytes += ret;
 	}
 
+	if (fanotify_is_mnt_event(event->mask)) {
+		ret = copy_mnt_info_to_user(event, buf, count);
+		if (ret < 0)
+			return ret;
+		buf += ret;
+		count -= ret;
+		total_bytes += ret;
+	}
 	return total_bytes;
 }
 
@@ -1449,6 +1482,8 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 	if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
 		return -EINVAL;
 
+	/* FIXME: check FAN_REPORT_MNT compatibility with other flags */
+
 	switch (event_f_flags & O_ACCMODE) {
 	case O_RDONLY:
 	case O_RDWR:
@@ -1718,6 +1753,9 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	case FAN_MARK_FILESYSTEM:
 		obj_type = FSNOTIFY_OBJ_TYPE_SB;
 		break;
+	case FAN_MARK_MNTNS:
+		obj_type = FSNOTIFY_OBJ_TYPE_MNTNS;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -1765,6 +1803,19 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 		return -EINVAL;
 	group = fd_file(f)->private_data;
 
+	/* Only report mount events on mnt namespace */
+	if (FAN_GROUP_FLAG(group, FAN_REPORT_MNT)) {
+		if (mask & ~FANOTIFY_MOUNT_EVENTS)
+			return -EINVAL;
+		if (mark_type != FAN_MARK_MNTNS)
+			return -EINVAL;
+	} else {
+		if (mask & FANOTIFY_MOUNT_EVENTS)
+			return -EINVAL;
+		if (mark_type == FAN_MARK_MNTNS)
+			return -EINVAL;
+	}
+
 	/*
 	 * An unprivileged user is not allowed to setup mount nor filesystem
 	 * marks.  This also includes setting up such marks by a group that
@@ -1802,7 +1853,7 @@ 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_EVENT_FLAGS) &&
+	if (mask & ~(FANOTIFY_FD_EVENTS|FANOTIFY_MOUNT_EVENTS|FANOTIFY_EVENT_FLAGS) &&
 	    (!fid_mode || mark_type == FAN_MARK_MOUNT))
 		return -EINVAL;
 
@@ -1855,8 +1906,14 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 		mnt = path.mnt;
 		if (mark_type == FAN_MARK_MOUNT)
 			obj = mnt;
-		else
+		else if (mark_type == FAN_MARK_FILESYSTEM)
 			obj = mnt->mnt_sb;
+		else /* if (mark_type == FAN_MARK_MNTNS) */ {
+			obj = mnt_ns_from_dentry(path.dentry);
+			ret = -EINVAL;
+			if (!obj)
+				goto path_put_and_out;
+		}
 	}
 
 	/*
@@ -1952,7 +2009,7 @@ static int __init fanotify_user_setup(void)
 				     FANOTIFY_DEFAULT_MAX_USER_MARKS);
 
 	BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
-	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 13);
+	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 14);
 	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 11);
 
 	fanotify_mark_cache = KMEM_CACHE(fanotify_mark,
@@ -1965,6 +2022,7 @@ static int __init fanotify_user_setup(void)
 		fanotify_perm_event_cachep =
 			KMEM_CACHE(fanotify_perm_event, SLAB_PANIC);
 	}
+	fanotify_mnt_event_cachep = KMEM_CACHE(fanotify_mnt_event, SLAB_PANIC);
 
 	fanotify_max_queued_events = FANOTIFY_DEFAULT_MAX_EVENTS;
 	init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS] =
diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
index dec553034027..505aabd62abb 100644
--- a/fs/notify/fdinfo.c
+++ b/fs/notify/fdinfo.c
@@ -123,6 +123,8 @@ static void fanotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark)
 
 		seq_printf(m, "fanotify sdev:%x mflags:%x mask:%x ignored_mask:%x\n",
 			   sb->s_dev, mflags, mark->mask, mark->ignore_mask);
+	} else if (mark->connector->type == FSNOTIFY_OBJ_TYPE_MNTNS) {
+		/* FIXME: print info for mntns */
 	}
 }
 
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index f976949d2634..2b2c3fd907c7 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -28,6 +28,11 @@ void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 	fsnotify_clear_marks_by_mount(mnt);
 }
 
+void __fsnotify_mntns_delete(struct mnt_namespace *mntns)
+{
+	fsnotify_clear_marks_by_mntns(mntns);
+}
+
 /**
  * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
  * @sb: superblock being unmounted.
@@ -402,7 +407,7 @@ static int send_to_group(__u32 mask, const void *data, int data_type,
 				     file_name, cookie, iter_info);
 }
 
-static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
+static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector *const *connp)
 {
 	struct fsnotify_mark_connector *conn;
 	struct hlist_node *node = NULL;
@@ -520,14 +525,15 @@ int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
 {
 	const struct path *path = fsnotify_data_path(data, data_type);
 	struct super_block *sb = fsnotify_data_sb(data, data_type);
-	struct fsnotify_sb_info *sbinfo = fsnotify_sb_info(sb);
+	const struct fsnotify_mnt *mnt_data = fsnotify_data_mnt(data, data_type);
+	struct fsnotify_sb_info *sbinfo = sb ? fsnotify_sb_info(sb) : NULL;
 	struct fsnotify_iter_info iter_info = {};
 	struct mount *mnt = NULL;
 	struct inode *inode2 = NULL;
 	struct dentry *moved;
 	int inode2_type;
 	int ret = 0;
-	__u32 test_mask, marks_mask;
+	__u32 test_mask, marks_mask = 0;
 
 	if (path)
 		mnt = real_mount(path->mnt);
@@ -560,17 +566,20 @@ int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
 	if ((!sbinfo || !sbinfo->sb_marks) &&
 	    (!mnt || !mnt->mnt_fsnotify_marks) &&
 	    (!inode || !inode->i_fsnotify_marks) &&
-	    (!inode2 || !inode2->i_fsnotify_marks))
+	    (!inode2 || !inode2->i_fsnotify_marks) &&
+	    (!mnt_data || !mnt_data->ns->n_fsnotify_marks))
 		return 0;
 
-	marks_mask = READ_ONCE(sb->s_fsnotify_mask);
+	if (sb)
+		marks_mask |= READ_ONCE(sb->s_fsnotify_mask);
 	if (mnt)
 		marks_mask |= READ_ONCE(mnt->mnt_fsnotify_mask);
 	if (inode)
 		marks_mask |= READ_ONCE(inode->i_fsnotify_mask);
 	if (inode2)
 		marks_mask |= READ_ONCE(inode2->i_fsnotify_mask);
-
+	if (mnt_data)
+		marks_mask |= READ_ONCE(mnt_data->ns->n_fsnotify_mask);
 
 	/*
 	 * If this is a modify event we may need to clear some ignore masks.
@@ -600,6 +609,10 @@ int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
 		iter_info.marks[inode2_type] =
 			fsnotify_first_mark(&inode2->i_fsnotify_marks);
 	}
+	if (mnt_data) {
+		iter_info.marks[FSNOTIFY_ITER_TYPE_MNTNS] =
+			fsnotify_first_mark(&mnt_data->ns->n_fsnotify_marks);
+	}
 
 	/*
 	 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
@@ -623,11 +636,31 @@ int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
 }
 EXPORT_SYMBOL_GPL(fsnotify);
 
+void fsnotify_mnt(__u32 mask, struct mnt_namespace *ns, struct vfsmount *mnt)
+{
+	struct fsnotify_mnt data = {
+		.ns = ns,
+		.mnt_id = real_mount(mnt)->mnt_id_unique,
+	};
+
+	if (WARN_ON_ONCE(!ns))
+		return;
+
+	/*
+	 * This is an optimization as well as making sure fsnotify_init() has
+	 * been called.
+	 */
+	if (!ns->n_fsnotify_marks)
+		return;
+
+	fsnotify(mask, &data, FSNOTIFY_EVENT_MNT, NULL, NULL, NULL, 0);
+}
+
 static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 23);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)
diff --git a/fs/notify/fsnotify.h b/fs/notify/fsnotify.h
index 663759ed6fbc..5950c7a67f41 100644
--- a/fs/notify/fsnotify.h
+++ b/fs/notify/fsnotify.h
@@ -33,6 +33,12 @@ static inline struct super_block *fsnotify_conn_sb(
 	return conn->obj;
 }
 
+static inline struct mnt_namespace *fsnotify_conn_mntns(
+				struct fsnotify_mark_connector *conn)
+{
+	return conn->obj;
+}
+
 static inline struct super_block *fsnotify_object_sb(void *obj,
 			enum fsnotify_obj_type obj_type)
 {
@@ -89,6 +95,11 @@ static inline void fsnotify_clear_marks_by_sb(struct super_block *sb)
 	fsnotify_destroy_marks(fsnotify_sb_marks(sb));
 }
 
+static inline void fsnotify_clear_marks_by_mntns(struct mnt_namespace *mntns)
+{
+	fsnotify_destroy_marks(&mntns->n_fsnotify_marks);
+}
+
 /*
  * update the dentry->d_flags of all of inode's children to indicate if inode cares
  * about events that happen to its children.
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 4981439e6209..798340db69d7 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -107,6 +107,8 @@ static fsnotify_connp_t *fsnotify_object_connp(void *obj,
 		return &real_mount(obj)->mnt_fsnotify_marks;
 	case FSNOTIFY_OBJ_TYPE_SB:
 		return fsnotify_sb_marks(obj);
+	case FSNOTIFY_OBJ_TYPE_MNTNS:
+		return &((struct mnt_namespace *)obj)->n_fsnotify_marks;
 	default:
 		return NULL;
 	}
@@ -120,6 +122,8 @@ static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn)
 		return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask;
 	else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
 		return &fsnotify_conn_sb(conn)->s_fsnotify_mask;
+	else if (conn->type == FSNOTIFY_OBJ_TYPE_MNTNS)
+		return &fsnotify_conn_mntns(conn)->n_fsnotify_mask;
 	return NULL;
 }
 
@@ -346,12 +350,15 @@ static void *fsnotify_detach_connector_from_object(
 		fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0;
 	} else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) {
 		fsnotify_conn_sb(conn)->s_fsnotify_mask = 0;
+	} else if (conn->type == FSNOTIFY_OBJ_TYPE_MNTNS) {
+		fsnotify_conn_mntns(conn)->n_fsnotify_mask = 0;
 	}
 
 	rcu_assign_pointer(*connp, NULL);
 	conn->obj = NULL;
 	conn->type = FSNOTIFY_OBJ_TYPE_DETACHED;
-	fsnotify_update_sb_watchers(sb, conn);
+	if (sb)
+		fsnotify_update_sb_watchers(sb, conn);
 
 	return inode;
 }
@@ -724,7 +731,7 @@ static int fsnotify_add_mark_list(struct fsnotify_mark *mark, void *obj,
 	 * Attach the sb info before attaching a connector to any object on sb.
 	 * The sb info will remain attached as long as sb lives.
 	 */
-	if (!fsnotify_sb_info(sb)) {
+	if (sb && !fsnotify_sb_info(sb)) {
 		err = fsnotify_attach_info_to_sb(sb);
 		if (err)
 			return err;
@@ -770,7 +777,8 @@ static int fsnotify_add_mark_list(struct fsnotify_mark *mark, void *obj,
 	/* mark should be the last entry.  last is the current last entry */
 	hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
 added:
-	fsnotify_update_sb_watchers(sb, conn);
+	if (sb)
+		fsnotify_update_sb_watchers(sb, conn);
 	/*
 	 * Since connector is attached to object using cmpxchg() we are
 	 * guaranteed that connector initialization is fully visible by anyone
diff --git a/fs/pnode.c b/fs/pnode.c
index a799e0315cc9..0c99de65724e 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -549,8 +549,10 @@ static void restore_mounts(struct list_head *to_restore)
 			mp = parent->mnt_mp;
 			parent = parent->mnt_parent;
 		}
-		if (parent != mnt->mnt_parent)
+		if (parent != mnt->mnt_parent) {
 			mnt_change_mountpoint(parent, mp, mnt);
+			add_notify(mnt);
+		}
 	}
 }
 
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index 89ff45bd6f01..d8699c165d94 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -25,7 +25,7 @@
 
 #define FANOTIFY_FID_BITS	(FAN_REPORT_DFID_NAME_TARGET)
 
-#define FANOTIFY_INFO_MODES	(FANOTIFY_FID_BITS | FAN_REPORT_PIDFD)
+#define FANOTIFY_INFO_MODES	(FANOTIFY_FID_BITS | FAN_REPORT_PIDFD | FAN_REPORT_MNT)
 
 /*
  * fanotify_init() flags that require CAP_SYS_ADMIN.
@@ -38,7 +38,8 @@
 					 FAN_REPORT_PIDFD | \
 					 FAN_REPORT_FD_ERROR | \
 					 FAN_UNLIMITED_QUEUE | \
-					 FAN_UNLIMITED_MARKS)
+					 FAN_UNLIMITED_MARKS | \
+					 FAN_REPORT_MNT)
 
 /*
  * fanotify_init() flags that are allowed for user without CAP_SYS_ADMIN.
@@ -58,7 +59,7 @@
 #define FANOTIFY_INTERNAL_GROUP_FLAGS	(FANOTIFY_UNPRIV)
 
 #define FANOTIFY_MARK_TYPE_BITS	(FAN_MARK_INODE | FAN_MARK_MOUNT | \
-				 FAN_MARK_FILESYSTEM)
+				 FAN_MARK_FILESYSTEM | FAN_MARK_MNTNS)
 
 #define FANOTIFY_MARK_CMD_BITS	(FAN_MARK_ADD | FAN_MARK_REMOVE | \
 				 FAN_MARK_FLUSH)
@@ -99,10 +100,13 @@
 /* Events that can only be reported with data type FSNOTIFY_EVENT_ERROR */
 #define FANOTIFY_ERROR_EVENTS	(FAN_FS_ERROR)
 
+#define FANOTIFY_MOUNT_EVENTS	(FAN_MNT_ATTACH | FAN_MNT_DETACH)
+
 /* Events that user can request to be notified on */
 #define FANOTIFY_EVENTS		(FANOTIFY_PATH_EVENTS | \
 				 FANOTIFY_INODE_EVENTS | \
-				 FANOTIFY_ERROR_EVENTS)
+				 FANOTIFY_ERROR_EVENTS | \
+				 FANOTIFY_MOUNT_EVENTS )
 
 /* Events that require a permission response from user */
 #define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM | \
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 278620e063ab..ea998551dd0d 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -255,6 +255,11 @@ static inline void fsnotify_vfsmount_delete(struct vfsmount *mnt)
 	__fsnotify_vfsmount_delete(mnt);
 }
 
+static inline void fsnotify_mntns_delete(struct mnt_namespace *mntns)
+{
+	__fsnotify_mntns_delete(mntns);
+}
+
 /*
  * fsnotify_inoderemove - an inode is going away
  */
@@ -463,4 +468,19 @@ static inline int fsnotify_sb_error(struct super_block *sb, struct inode *inode,
 			NULL, NULL, NULL, 0);
 }
 
+static inline void fsnotify_mnt_attach(struct mnt_namespace *ns, struct vfsmount *mnt)
+{
+	fsnotify_mnt(FS_MNT_ATTACH, ns, mnt);
+}
+
+static inline void fsnotify_mnt_detach(struct mnt_namespace *ns, struct vfsmount *mnt)
+{
+	fsnotify_mnt(FS_MNT_DETACH, ns, mnt);
+}
+
+static inline void fsnotify_mnt_move(struct mnt_namespace *ns, struct vfsmount *mnt)
+{
+	fsnotify_mnt(FS_MNT_MOVE, ns, mnt);
+}
+
 #endif	/* _LINUX_FS_NOTIFY_H */
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 3ecf7768e577..b84ac1ed9721 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -56,6 +56,10 @@
 #define FS_ACCESS_PERM		0x00020000	/* access event in a permissions hook */
 #define FS_OPEN_EXEC_PERM	0x00040000	/* open/exec event in a permission hook */
 
+#define FS_MNT_ATTACH		0x00100000	/* Mount was attached */
+#define FS_MNT_DETACH		0x00200000	/* Mount was detached */
+#define FS_MNT_MOVE		(FS_MNT_ATTACH | FS_MNT_DETACH)
+
 /*
  * Set on inode mark that cares about things that happen to its children.
  * Always set for dnotify and inotify.
@@ -102,7 +106,7 @@
 			     FS_EVENTS_POSS_ON_CHILD | \
 			     FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
-			     FS_ERROR)
+			     FS_ERROR | FS_MNT_ATTACH | FS_MNT_DETACH)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define ALL_FSNOTIFY_FLAGS  (FS_ISDIR | FS_EVENT_ON_CHILD | FS_DN_MULTISHOT)
@@ -288,6 +292,7 @@ enum fsnotify_data_type {
 	FSNOTIFY_EVENT_PATH,
 	FSNOTIFY_EVENT_INODE,
 	FSNOTIFY_EVENT_DENTRY,
+	FSNOTIFY_EVENT_MNT,
 	FSNOTIFY_EVENT_ERROR,
 };
 
@@ -297,6 +302,11 @@ struct fs_error_report {
 	struct super_block *sb;
 };
 
+struct fsnotify_mnt {
+	const struct mnt_namespace *ns;
+	u64 mnt_id;
+};
+
 static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
 {
 	switch (data_type) {
@@ -354,6 +364,24 @@ static inline struct super_block *fsnotify_data_sb(const void *data,
 	}
 }
 
+static inline const struct fsnotify_mnt *fsnotify_data_mnt(const void *data,
+							   int data_type)
+{
+	switch (data_type) {
+	case FSNOTIFY_EVENT_MNT:
+		return data;
+	default:
+		return NULL;
+	}
+}
+
+static inline u64 fsnotify_data_mnt_id(const void *data, int data_type)
+{
+	const struct fsnotify_mnt *mnt_data = fsnotify_data_mnt(data, data_type);
+
+	return mnt_data ? mnt_data->mnt_id : 0;
+}
+
 static inline struct fs_error_report *fsnotify_data_error_report(
 							const void *data,
 							int data_type)
@@ -379,6 +407,7 @@ enum fsnotify_iter_type {
 	FSNOTIFY_ITER_TYPE_SB,
 	FSNOTIFY_ITER_TYPE_PARENT,
 	FSNOTIFY_ITER_TYPE_INODE2,
+	FSNOTIFY_ITER_TYPE_MNTNS,
 	FSNOTIFY_ITER_TYPE_COUNT
 };
 
@@ -388,6 +417,7 @@ enum fsnotify_obj_type {
 	FSNOTIFY_OBJ_TYPE_INODE,
 	FSNOTIFY_OBJ_TYPE_VFSMOUNT,
 	FSNOTIFY_OBJ_TYPE_SB,
+	FSNOTIFY_OBJ_TYPE_MNTNS,
 	FSNOTIFY_OBJ_TYPE_COUNT,
 	FSNOTIFY_OBJ_TYPE_DETACHED = FSNOTIFY_OBJ_TYPE_COUNT
 };
@@ -572,8 +602,10 @@ extern int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data
 extern void __fsnotify_inode_delete(struct inode *inode);
 extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
 extern void fsnotify_sb_delete(struct super_block *sb);
+extern void __fsnotify_mntns_delete(struct mnt_namespace *mntns);
 extern void fsnotify_sb_free(struct super_block *sb);
 extern u32 fsnotify_get_cookie(void);
+extern void fsnotify_mnt(__u32 mask, struct mnt_namespace *ns, struct vfsmount *mnt);
 
 static inline __u32 fsnotify_parent_needed_mask(__u32 mask)
 {
@@ -879,6 +911,9 @@ static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
 static inline void fsnotify_sb_delete(struct super_block *sb)
 {}
 
+static inline void __fsnotify_mntns_delete(struct mnt_namespace *mntns)
+{}
+
 static inline void fsnotify_sb_free(struct super_block *sb)
 {}
 
@@ -893,6 +928,9 @@ static inline u32 fsnotify_get_cookie(void)
 static inline void fsnotify_unmount_inodes(struct super_block *sb)
 {}
 
+static inline void fsnotify_mnt(__u32 mask, struct mnt_namespace *ns, struct vfsmount *mnt)
+{}
+
 #endif	/* CONFIG_FSNOTIFY */
 
 #endif	/* __KERNEL __ */
diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h
index 70b366b64816..05bc01c0f38a 100644
--- a/include/linux/mnt_namespace.h
+++ b/include/linux/mnt_namespace.h
@@ -10,6 +10,7 @@ struct mnt_namespace;
 struct fs_struct;
 struct user_namespace;
 struct ns_common;
+struct vfsmount;
 
 extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,
 		struct user_namespace *, struct fs_struct *);
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index 34f221d3a1b9..332ef8532390 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -25,6 +25,8 @@
 #define FAN_OPEN_PERM		0x00010000	/* File open in perm check */
 #define FAN_ACCESS_PERM		0x00020000	/* File accessed in perm check */
 #define FAN_OPEN_EXEC_PERM	0x00040000	/* File open/exec in perm check */
+#define FAN_MNT_ATTACH		0x00100000	/* Mount was attached */
+#define FAN_MNT_DETACH		0x00200000	/* Mount was detached */
 
 #define FAN_EVENT_ON_CHILD	0x08000000	/* Interested in child events */
 
@@ -61,6 +63,7 @@
 #define FAN_REPORT_NAME		0x00000800	/* Report events with name */
 #define FAN_REPORT_TARGET_FID	0x00001000	/* Report dirent target id  */
 #define FAN_REPORT_FD_ERROR	0x00002000	/* event->fd can report error */
+#define FAN_REPORT_MNT		0x00004000	/* Report mount events */
 
 /* Convenience macro - FAN_REPORT_NAME requires FAN_REPORT_DIR_FID */
 #define FAN_REPORT_DFID_NAME	(FAN_REPORT_DIR_FID | FAN_REPORT_NAME)
@@ -91,6 +94,7 @@
 #define FAN_MARK_INODE		0x00000000
 #define FAN_MARK_MOUNT		0x00000010
 #define FAN_MARK_FILESYSTEM	0x00000100
+#define FAN_MARK_MNTNS		0x00000110
 
 /*
  * Convenience macro - FAN_MARK_IGNORE requires FAN_MARK_IGNORED_SURV_MODIFY
@@ -143,6 +147,7 @@ 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_MNT		6
 
 /* Special info types for FAN_RENAME */
 #define FAN_EVENT_INFO_TYPE_OLD_DFID_NAME	10
@@ -189,6 +194,11 @@ struct fanotify_event_info_error {
 	__u32 error_count;
 };
 
+struct fanotify_event_info_mnt {
+	struct fanotify_event_info_header hdr;
+	__u64 mnt_id;
+};
+
 /*
  * User space may need to record additional information about its decision.
  * The extra information type records what kind of information is included.
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 366c87a40bd1..aab8972a3124 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:
+		/* FIXME: Is this correct??? */
+		perm = FILE__WATCH;
+		break;
 	default:
 		return -EINVAL;
 	}
-- 
2.47.0