Merge tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull idmapped mounts from Christian Brauner:
 "This introduces idmapped mounts which has been in the making for some
  time. Simply put, different mounts can expose the same file or
  directory with different ownership. This initial implementation comes
  with ports for fat, ext4 and with Christoph's port for xfs with more
  filesystems being actively worked on by independent people and
  maintainers.

  Idmapping mounts handle a wide range of long standing use-cases. Here
  are just a few:

   - Idmapped mounts make it possible to easily share files between
     multiple users or multiple machines especially in complex
     scenarios. For example, idmapped mounts will be used in the
     implementation of portable home directories in
     systemd-homed.service(8) where they allow users to move their home
     directory to an external storage device and use it on multiple
     computers where they are assigned different uids and gids. This
     effectively makes it possible to assign random uids and gids at
     login time.

   - It is possible to share files from the host with unprivileged
     containers without having to change ownership permanently through
     chown(2).

   - It is possible to idmap a container's rootfs and without having to
     mangle every file. For example, Chromebooks use it to share the
     user's Download folder with their unprivileged containers in their
     Linux subsystem.

   - It is possible to share files between containers with
     non-overlapping idmappings.

   - Filesystem that lack a proper concept of ownership such as fat can
     use idmapped mounts to implement discretionary access (DAC)
     permission checking.

   - They allow users to efficiently changing ownership on a per-mount
     basis without having to (recursively) chown(2) all files. In
     contrast to chown (2) changing ownership of large sets of files is
     instantenous with idmapped mounts. This is especially useful when
     ownership of a whole root filesystem of a virtual machine or
     container is changed. With idmapped mounts a single syscall
     mount_setattr syscall will be sufficient to change the ownership of
     all files.

   - Idmapped mounts always take the current ownership into account as
     idmappings specify what a given uid or gid is supposed to be mapped
     to. This contrasts with the chown(2) syscall which cannot by itself
     take the current ownership of the files it changes into account. It
     simply changes the ownership to the specified uid and gid. This is
     especially problematic when recursively chown(2)ing a large set of
     files which is commong with the aforementioned portable home
     directory and container and vm scenario.

   - Idmapped mounts allow to change ownership locally, restricting it
     to specific mounts, and temporarily as the ownership changes only
     apply as long as the mount exists.

  Several userspace projects have either already put up patches and
  pull-requests for this feature or will do so should you decide to pull
  this:

   - systemd: In a wide variety of scenarios but especially right away
     in their implementation of portable home directories.

         https://systemd.io/HOME_DIRECTORY/

   - container runtimes: containerd, runC, LXD:To share data between
     host and unprivileged containers, unprivileged and privileged
     containers, etc. The pull request for idmapped mounts support in
     containerd, the default Kubernetes runtime is already up for quite
     a while now: https://github.com/containerd/containerd/pull/4734

   - The virtio-fs developers and several users have expressed interest
     in using this feature with virtual machines once virtio-fs is
     ported.

   - ChromeOS: Sharing host-directories with unprivileged containers.

  I've tightly synced with all those projects and all of those listed
  here have also expressed their need/desire for this feature on the
  mailing list. For more info on how people use this there's a bunch of
  talks about this too. Here's just two recent ones:

      https://www.cncf.io/wp-content/uploads/2020/12/Rootless-Containers-in-Gitpod.pdf
      https://fosdem.org/2021/schedule/event/containers_idmap/

  This comes with an extensive xfstests suite covering both ext4 and
  xfs:

      https://git.kernel.org/brauner/xfstests-dev/h/idmapped_mounts

  It covers truncation, creation, opening, xattrs, vfscaps, setid
  execution, setgid inheritance and more both with idmapped and
  non-idmapped mounts. It already helped to discover an unrelated xfs
  setgid inheritance bug which has since been fixed in mainline. It will
  be sent for inclusion with the xfstests project should you decide to
  merge this.

  In order to support per-mount idmappings vfsmounts are marked with
  user namespaces. The idmapping of the user namespace will be used to
  map the ids of vfs objects when they are accessed through that mount.
  By default all vfsmounts are marked with the initial user namespace.
  The initial user namespace is used to indicate that a mount is not
  idmapped. All operations behave as before and this is verified in the
  testsuite.

  Based on prior discussions we want to attach the whole user namespace
  and not just a dedicated idmapping struct. This allows us to reuse all
  the helpers that already exist for dealing with idmappings instead of
  introducing a whole new range of helpers. In addition, if we decide in
  the future that we are confident enough to enable unprivileged users
  to setup idmapped mounts the permission checking can take into account
  whether the caller is privileged in the user namespace the mount is
  currently marked with.

  The user namespace the mount will be marked with can be specified by
  passing a file descriptor refering to the user namespace as an
  argument to the new mount_setattr() syscall together with the new
  MOUNT_ATTR_IDMAP flag. The system call follows the openat2() pattern
  of extensibility.

  The following conditions must be met in order to create an idmapped
  mount:

   - The caller must currently have the CAP_SYS_ADMIN capability in the
     user namespace the underlying filesystem has been mounted in.

   - The underlying filesystem must support idmapped mounts.

   - The mount must not already be idmapped. This also implies that the
     idmapping of a mount cannot be altered once it has been idmapped.

   - The mount must be a detached/anonymous mount, i.e. it must have
     been created by calling open_tree() with the OPEN_TREE_CLONE flag
     and it must not already have been visible in the filesystem.

  The last two points guarantee easier semantics for userspace and the
  kernel and make the implementation significantly simpler.

  By default vfsmounts are marked with the initial user namespace and no
  behavioral or performance changes are observed.

  The manpage with a detailed description can be found here:

      https://git.kernel.org/brauner/man-pages/c/1d7b902e2875a1ff342e036a9f866a995640aea8

  In order to support idmapped mounts, filesystems need to be changed
  and mark themselves with the FS_ALLOW_IDMAP flag in fs_flags. The
  patches to convert individual filesystem are not very large or
  complicated overall as can be seen from the included fat, ext4, and
  xfs ports. Patches for other filesystems are actively worked on and
  will be sent out separately. The xfstestsuite can be used to verify
  that port has been done correctly.

  The mount_setattr() syscall is motivated independent of the idmapped
  mounts patches and it's been around since July 2019. One of the most
  valuable features of the new mount api is the ability to perform
  mounts based on file descriptors only.

  Together with the lookup restrictions available in the openat2()
  RESOLVE_* flag namespace which we added in v5.6 this is the first time
  we are close to hardened and race-free (e.g. symlinks) mounting and
  path resolution.

  While userspace has started porting to the new mount api to mount
  proper filesystems and create new bind-mounts it is currently not
  possible to change mount options of an already existing bind mount in
  the new mount api since the mount_setattr() syscall is missing.

  With the addition of the mount_setattr() syscall we remove this last
  restriction and userspace can now fully port to the new mount api,
  covering every use-case the old mount api could. We also add the
  crucial ability to recursively change mount options for a whole mount
  tree, both removing and adding mount options at the same time. This
  syscall has been requested multiple times by various people and
  projects.

  There is a simple tool available at

      https://github.com/brauner/mount-idmapped

  that allows to create idmapped mounts so people can play with this
  patch series. I'll add support for the regular mount binary should you
  decide to pull this in the following weeks:

  Here's an example to a simple idmapped mount of another user's home
  directory:

	u1001@f2-vm:/$ sudo ./mount --idmap both:1000:1001:1 /home/ubuntu/ /mnt

	u1001@f2-vm:/$ ls -al /home/ubuntu/
	total 28
	drwxr-xr-x 2 ubuntu ubuntu 4096 Oct 28 22:07 .
	drwxr-xr-x 4 root   root   4096 Oct 28 04:00 ..
	-rw------- 1 ubuntu ubuntu 3154 Oct 28 22:12 .bash_history
	-rw-r--r-- 1 ubuntu ubuntu  220 Feb 25  2020 .bash_logout
	-rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25  2020 .bashrc
	-rw-r--r-- 1 ubuntu ubuntu  807 Feb 25  2020 .profile
	-rw-r--r-- 1 ubuntu ubuntu    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ ls -al /mnt/
	total 28
	drwxr-xr-x  2 u1001 u1001 4096 Oct 28 22:07 .
	drwxr-xr-x 29 root  root  4096 Oct 28 22:01 ..
	-rw-------  1 u1001 u1001 3154 Oct 28 22:12 .bash_history
	-rw-r--r--  1 u1001 u1001  220 Feb 25  2020 .bash_logout
	-rw-r--r--  1 u1001 u1001 3771 Feb 25  2020 .bashrc
	-rw-r--r--  1 u1001 u1001  807 Feb 25  2020 .profile
	-rw-r--r--  1 u1001 u1001    0 Oct 16 16:11 .sudo_as_admin_successful
	-rw-------  1 u1001 u1001 1144 Oct 28 00:43 .viminfo

	u1001@f2-vm:/$ touch /mnt/my-file

	u1001@f2-vm:/$ setfacl -m u:1001:rwx /mnt/my-file

	u1001@f2-vm:/$ sudo setcap -n 1001 cap_net_raw+ep /mnt/my-file

	u1001@f2-vm:/$ ls -al /mnt/my-file
	-rw-rwxr--+ 1 u1001 u1001 0 Oct 28 22:14 /mnt/my-file

	u1001@f2-vm:/$ ls -al /home/ubuntu/my-file
	-rw-rwxr--+ 1 ubuntu ubuntu 0 Oct 28 22:14 /home/ubuntu/my-file

	u1001@f2-vm:/$ getfacl /mnt/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: mnt/my-file
	# owner: u1001
	# group: u1001
	user::rw-
	user:u1001:rwx
	group::rw-
	mask::rwx
	other::r--

	u1001@f2-vm:/$ getfacl /home/ubuntu/my-file
	getfacl: Removing leading '/' from absolute path names
	# file: home/ubuntu/my-file
	# owner: ubuntu
	# group: ubuntu
	user::rw-
	user:ubuntu:rwx
	group::rw-
	mask::rwx
	other::r--"

* tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: (41 commits)
  xfs: remove the possibly unused mp variable in xfs_file_compat_ioctl
  xfs: support idmapped mounts
  ext4: support idmapped mounts
  fat: handle idmapped mounts
  tests: add mount_setattr() selftests
  fs: introduce MOUNT_ATTR_IDMAP
  fs: add mount_setattr()
  fs: add attr_flags_to_mnt_flags helper
  fs: split out functions to hold writers
  namespace: only take read lock in do_reconfigure_mnt()
  mount: make {lock,unlock}_mount_hash() static
  namespace: take lock_mount_hash() directly when changing flags
  nfs: do not export idmapped mounts
  overlayfs: do not mount on top of idmapped mounts
  ecryptfs: do not mount on top of idmapped mounts
  ima: handle idmapped mounts
  apparmor: handle idmapped mounts
  fs: make helpers idmap mount aware
  exec: handle idmapped mounts
  would_dump: handle idmapped mounts
  ...

7 files changed, 90 insertions, 66 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 0fed532efa68..0b2891c6c71e 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -93,9 +93,9 @@ int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
 			continue; /* Discard */
 		}
 retry:
-		size = vfs_getxattr(old, name, value, value_size);
+		size = vfs_getxattr(&init_user_ns, old, name, value, value_size);
 		if (size == -ERANGE)
-			size = vfs_getxattr(old, name, NULL, 0);
+			size = vfs_getxattr(&init_user_ns, old, name, NULL, 0);
 
 		if (size < 0) {
 			error = size;
@@ -115,7 +115,7 @@ retry:
 			goto retry;
 		}
 
-		error = vfs_setxattr(new, name, value, size, 0);
+		error = vfs_setxattr(&init_user_ns, new, name, value, size, 0);
 		if (error) {
 			if (error != -EOPNOTSUPP || ovl_must_copy_xattr(name))
 				break;
@@ -236,7 +236,7 @@ static int ovl_set_size(struct dentry *upperdentry, struct kstat *stat)
 		.ia_size = stat->size,
 	};
 
-	return notify_change(upperdentry, &attr, NULL);
+	return notify_change(&init_user_ns, upperdentry, &attr, NULL);
 }
 
 static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
@@ -248,7 +248,7 @@ static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
 		.ia_mtime = stat->mtime,
 	};
 
-	return notify_change(upperdentry, &attr, NULL);
+	return notify_change(&init_user_ns, upperdentry, &attr, NULL);
 }
 
 int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
@@ -260,7 +260,7 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
 			.ia_valid = ATTR_MODE,
 			.ia_mode = stat->mode,
 		};
-		err = notify_change(upperdentry, &attr, NULL);
+		err = notify_change(&init_user_ns, upperdentry, &attr, NULL);
 	}
 	if (!err) {
 		struct iattr attr = {
@@ -268,7 +268,7 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
 			.ia_uid = stat->uid,
 			.ia_gid = stat->gid,
 		};
-		err = notify_change(upperdentry, &attr, NULL);
+		err = notify_change(&init_user_ns, upperdentry, &attr, NULL);
 	}
 	if (!err)
 		ovl_set_timestamps(upperdentry, stat);
@@ -796,7 +796,7 @@ static ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value)
 	ssize_t res;
 	char *buf;
 
-	res = vfs_getxattr(dentry, name, NULL, 0);
+	res = vfs_getxattr(&init_user_ns, dentry, name, NULL, 0);
 	if (res == -ENODATA || res == -EOPNOTSUPP)
 		res = 0;
 
@@ -805,7 +805,7 @@ static ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value)
 		if (!buf)
 			return -ENOMEM;
 
-		res = vfs_getxattr(dentry, name, buf, res);
+		res = vfs_getxattr(&init_user_ns, dentry, name, buf, res);
 		if (res < 0)
 			kfree(buf);
 		else
@@ -847,8 +847,8 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
 	 * don't want that to happen for normal copy-up operation.
 	 */
 	if (capability) {
-		err = vfs_setxattr(upperpath.dentry, XATTR_NAME_CAPS,
-				   capability, cap_size, 0);
+		err = vfs_setxattr(&init_user_ns, upperpath.dentry,
+				   XATTR_NAME_CAPS, capability, cap_size, 0);
 		if (err)
 			goto out_free;
 	}
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index d1efa3a5a503..836f14b9d3a6 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -449,7 +449,7 @@ static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
 	if (err < 0)
 		goto out_free;
 
-	err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
+	err = vfs_setxattr(&init_user_ns, upperdentry, name, buffer, size, XATTR_CREATE);
 out_free:
 	kfree(buffer);
 	return err;
@@ -508,7 +508,7 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 			.ia_mode = cattr->mode,
 		};
 		inode_lock(newdentry->d_inode);
-		err = notify_change(newdentry, &attr, NULL);
+		err = notify_change(&init_user_ns, newdentry, &attr, NULL);
 		inode_unlock(newdentry->d_inode);
 		if (err)
 			goto out_cleanup;
@@ -636,7 +636,7 @@ static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 	inode->i_state |= I_CREATING;
 	spin_unlock(&inode->i_lock);
 
-	inode_init_owner(inode, dentry->d_parent->d_inode, mode);
+	inode_init_owner(&init_user_ns, inode, dentry->d_parent->d_inode, mode);
 	attr.mode = inode->i_mode;
 
 	err = ovl_create_or_link(dentry, inode, &attr, false);
@@ -650,19 +650,20 @@ out:
 	return err;
 }
 
-static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
-		      bool excl)
+static int ovl_create(struct user_namespace *mnt_userns, struct inode *dir,
+		      struct dentry *dentry, umode_t mode, bool excl)
 {
 	return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 }
 
-static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
+static int ovl_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+		     struct dentry *dentry, umode_t mode)
 {
 	return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
 }
 
-static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
-		     dev_t rdev)
+static int ovl_mknod(struct user_namespace *mnt_userns, struct inode *dir,
+		     struct dentry *dentry, umode_t mode, dev_t rdev)
 {
 	/* Don't allow creation of "whiteout" on overlay */
 	if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
@@ -671,8 +672,8 @@ static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 	return ovl_create_object(dentry, mode, rdev, NULL);
 }
 
-static int ovl_symlink(struct inode *dir, struct dentry *dentry,
-		       const char *link)
+static int ovl_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *dentry, const char *link)
 {
 	return ovl_create_object(dentry, S_IFLNK, 0, link);
 }
@@ -821,9 +822,9 @@ static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
 		goto out_dput_upper;
 
 	if (is_dir)
-		err = vfs_rmdir(dir, upper);
+		err = vfs_rmdir(&init_user_ns, dir, upper);
 	else
-		err = vfs_unlink(dir, upper, NULL);
+		err = vfs_unlink(&init_user_ns, dir, upper, NULL);
 	ovl_dir_modified(dentry->d_parent, ovl_type_origin(dentry));
 
 	/*
@@ -1069,9 +1070,9 @@ static int ovl_set_redirect(struct dentry *dentry, bool samedir)
 	return err;
 }
 
-static int ovl_rename(struct inode *olddir, struct dentry *old,
-		      struct inode *newdir, struct dentry *new,
-		      unsigned int flags)
+static int ovl_rename(struct user_namespace *mnt_userns, struct inode *olddir,
+		      struct dentry *old, struct inode *newdir,
+		      struct dentry *new, unsigned int flags)
 {
 	int err;
 	struct dentry *old_upperdir;
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 077d3ad343f6..dbfb35fb0ff7 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -50,11 +50,11 @@ static struct file *ovl_open_realfile(const struct file *file,
 		acc_mode |= MAY_APPEND;
 
 	old_cred = ovl_override_creds(inode->i_sb);
-	err = inode_permission(realinode, MAY_OPEN | acc_mode);
+	err = inode_permission(&init_user_ns, realinode, MAY_OPEN | acc_mode);
 	if (err) {
 		realfile = ERR_PTR(err);
 	} else {
-		if (!inode_owner_or_capable(realinode))
+		if (!inode_owner_or_capable(&init_user_ns, realinode))
 			flags &= ~O_NOATIME;
 
 		realfile = open_with_fake_path(&file->f_path, flags, realinode,
@@ -521,7 +521,7 @@ static long ovl_ioctl_set_flags(struct file *file, unsigned int cmd,
 	long ret;
 	struct inode *inode = file_inode(file);
 
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		return -EACCES;
 
 	ret = mnt_want_write_file(file);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index cf41bcb664bc..003cf83bf78a 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -14,14 +14,15 @@
 #include "overlayfs.h"
 
 
-int ovl_setattr(struct dentry *dentry, struct iattr *attr)
+int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct iattr *attr)
 {
 	int err;
 	bool full_copy_up = false;
 	struct dentry *upperdentry;
 	const struct cred *old_cred;
 
-	err = setattr_prepare(dentry, attr);
+	err = setattr_prepare(&init_user_ns, dentry, attr);
 	if (err)
 		return err;
 
@@ -79,7 +80,7 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
 
 		inode_lock(upperdentry->d_inode);
 		old_cred = ovl_override_creds(dentry->d_sb);
-		err = notify_change(upperdentry, attr, NULL);
+		err = notify_change(&init_user_ns, upperdentry, attr, NULL);
 		revert_creds(old_cred);
 		if (!err)
 			ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
@@ -154,8 +155,8 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
 	return 0;
 }
 
-int ovl_getattr(const struct path *path, struct kstat *stat,
-		u32 request_mask, unsigned int flags)
+int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
+		struct kstat *stat, u32 request_mask, unsigned int flags)
 {
 	struct dentry *dentry = path->dentry;
 	enum ovl_path_type type;
@@ -277,7 +278,8 @@ out:
 	return err;
 }
 
-int ovl_permission(struct inode *inode, int mask)
+int ovl_permission(struct user_namespace *mnt_userns,
+		   struct inode *inode, int mask)
 {
 	struct inode *upperinode = ovl_inode_upper(inode);
 	struct inode *realinode = upperinode ?: ovl_inode_lower(inode);
@@ -294,7 +296,7 @@ int ovl_permission(struct inode *inode, int mask)
 	 * Check overlay inode with the creds of task and underlying inode
 	 * with creds of mounter
 	 */
-	err = generic_permission(inode, mask);
+	err = generic_permission(&init_user_ns, inode, mask);
 	if (err)
 		return err;
 
@@ -305,7 +307,7 @@ int ovl_permission(struct inode *inode, int mask)
 		/* Make sure mounter can read file for copy up later */
 		mask |= MAY_READ;
 	}
-	err = inode_permission(realinode, mask);
+	err = inode_permission(&init_user_ns, realinode, mask);
 	revert_creds(old_cred);
 
 	return err;
@@ -353,7 +355,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 
 	if (!value && !upperdentry) {
 		old_cred = ovl_override_creds(dentry->d_sb);
-		err = vfs_getxattr(realdentry, name, NULL, 0);
+		err = vfs_getxattr(&init_user_ns, realdentry, name, NULL, 0);
 		revert_creds(old_cred);
 		if (err < 0)
 			goto out_drop_write;
@@ -369,10 +371,11 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 
 	old_cred = ovl_override_creds(dentry->d_sb);
 	if (value)
-		err = vfs_setxattr(realdentry, name, value, size, flags);
+		err = vfs_setxattr(&init_user_ns, realdentry, name, value, size,
+				   flags);
 	else {
 		WARN_ON(flags != XATTR_REPLACE);
-		err = vfs_removexattr(realdentry, name);
+		err = vfs_removexattr(&init_user_ns, realdentry, name);
 	}
 	revert_creds(old_cred);
 
@@ -394,7 +397,7 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
 		ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry);
 
 	old_cred = ovl_override_creds(dentry->d_sb);
-	res = vfs_getxattr(realdentry, name, value, size);
+	res = vfs_getxattr(&init_user_ns, realdentry, name, value, size);
 	revert_creds(old_cred);
 	return res;
 }
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index cb4e2d60ecf9..95cff83786a5 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -123,7 +123,7 @@ static inline const char *ovl_xattr(struct ovl_fs *ofs, enum ovl_xattr ox)
 
 static inline int ovl_do_rmdir(struct inode *dir, struct dentry *dentry)
 {
-	int err = vfs_rmdir(dir, dentry);
+	int err = vfs_rmdir(&init_user_ns, dir, dentry);
 
 	pr_debug("rmdir(%pd2) = %i\n", dentry, err);
 	return err;
@@ -131,7 +131,7 @@ static inline int ovl_do_rmdir(struct inode *dir, struct dentry *dentry)
 
 static inline int ovl_do_unlink(struct inode *dir, struct dentry *dentry)
 {
-	int err = vfs_unlink(dir, dentry, NULL);
+	int err = vfs_unlink(&init_user_ns, dir, dentry, NULL);
 
 	pr_debug("unlink(%pd2) = %i\n", dentry, err);
 	return err;
@@ -140,7 +140,7 @@ static inline int ovl_do_unlink(struct inode *dir, struct dentry *dentry)
 static inline int ovl_do_link(struct dentry *old_dentry, struct inode *dir,
 			      struct dentry *new_dentry)
 {
-	int err = vfs_link(old_dentry, dir, new_dentry, NULL);
+	int err = vfs_link(old_dentry, &init_user_ns, dir, new_dentry, NULL);
 
 	pr_debug("link(%pd2, %pd2) = %i\n", old_dentry, new_dentry, err);
 	return err;
@@ -149,7 +149,7 @@ static inline int ovl_do_link(struct dentry *old_dentry, struct inode *dir,
 static inline int ovl_do_create(struct inode *dir, struct dentry *dentry,
 				umode_t mode)
 {
-	int err = vfs_create(dir, dentry, mode, true);
+	int err = vfs_create(&init_user_ns, dir, dentry, mode, true);
 
 	pr_debug("create(%pd2, 0%o) = %i\n", dentry, mode, err);
 	return err;
@@ -158,7 +158,7 @@ static inline int ovl_do_create(struct inode *dir, struct dentry *dentry,
 static inline int ovl_do_mkdir(struct inode *dir, struct dentry *dentry,
 			       umode_t mode)
 {
-	int err = vfs_mkdir(dir, dentry, mode);
+	int err = vfs_mkdir(&init_user_ns, dir, dentry, mode);
 	pr_debug("mkdir(%pd2, 0%o) = %i\n", dentry, mode, err);
 	return err;
 }
@@ -166,7 +166,7 @@ static inline int ovl_do_mkdir(struct inode *dir, struct dentry *dentry,
 static inline int ovl_do_mknod(struct inode *dir, struct dentry *dentry,
 			       umode_t mode, dev_t dev)
 {
-	int err = vfs_mknod(dir, dentry, mode, dev);
+	int err = vfs_mknod(&init_user_ns, dir, dentry, mode, dev);
 
 	pr_debug("mknod(%pd2, 0%o, 0%o) = %i\n", dentry, mode, dev, err);
 	return err;
@@ -175,7 +175,7 @@ static inline int ovl_do_mknod(struct inode *dir, struct dentry *dentry,
 static inline int ovl_do_symlink(struct inode *dir, struct dentry *dentry,
 				 const char *oldname)
 {
-	int err = vfs_symlink(dir, dentry, oldname);
+	int err = vfs_symlink(&init_user_ns, dir, dentry, oldname);
 
 	pr_debug("symlink(\"%s\", %pd2) = %i\n", oldname, dentry, err);
 	return err;
@@ -186,7 +186,7 @@ static inline ssize_t ovl_do_getxattr(struct ovl_fs *ofs, struct dentry *dentry,
 				      size_t size)
 {
 	const char *name = ovl_xattr(ofs, ox);
-	return vfs_getxattr(dentry, name, value, size);
+	return vfs_getxattr(&init_user_ns, dentry, name, value, size);
 }
 
 static inline int ovl_do_setxattr(struct ovl_fs *ofs, struct dentry *dentry,
@@ -194,7 +194,7 @@ static inline int ovl_do_setxattr(struct ovl_fs *ofs, struct dentry *dentry,
 				  size_t size)
 {
 	const char *name = ovl_xattr(ofs, ox);
-	int err = vfs_setxattr(dentry, name, value, size, 0);
+	int err = vfs_setxattr(&init_user_ns, dentry, name, value, size, 0);
 	pr_debug("setxattr(%pd2, \"%s\", \"%*pE\", %zu, 0) = %i\n",
 		 dentry, name, min((int)size, 48), value, size, err);
 	return err;
@@ -204,7 +204,7 @@ static inline int ovl_do_removexattr(struct ovl_fs *ofs, struct dentry *dentry,
 				     enum ovl_xattr ox)
 {
 	const char *name = ovl_xattr(ofs, ox);
-	int err = vfs_removexattr(dentry, name);
+	int err = vfs_removexattr(&init_user_ns, dentry, name);
 	pr_debug("removexattr(%pd2, \"%s\") = %i\n", dentry, name, err);
 	return err;
 }
@@ -214,9 +214,18 @@ static inline int ovl_do_rename(struct inode *olddir, struct dentry *olddentry,
 				unsigned int flags)
 {
 	int err;
+	struct renamedata rd = {
+		.old_mnt_userns	= &init_user_ns,
+		.old_dir 	= olddir,
+		.old_dentry 	= olddentry,
+		.new_mnt_userns	= &init_user_ns,
+		.new_dir 	= newdir,
+		.new_dentry 	= newdentry,
+		.flags 		= flags,
+	};
 
 	pr_debug("rename(%pd2, %pd2, 0x%x)\n", olddentry, newdentry, flags);
-	err = vfs_rename(olddir, olddentry, newdir, newdentry, NULL, flags);
+	err = vfs_rename(&rd);
 	if (err) {
 		pr_debug("...rename(%pd2, %pd2, ...) = %i\n",
 			 olddentry, newdentry, err);
@@ -226,14 +235,14 @@ static inline int ovl_do_rename(struct inode *olddir, struct dentry *olddentry,
 
 static inline int ovl_do_whiteout(struct inode *dir, struct dentry *dentry)
 {
-	int err = vfs_whiteout(dir, dentry);
+	int err = vfs_whiteout(&init_user_ns, dir, dentry);
 	pr_debug("whiteout(%pd2) = %i\n", dentry, err);
 	return err;
 }
 
 static inline struct dentry *ovl_do_tmpfile(struct dentry *dentry, umode_t mode)
 {
-	struct dentry *ret = vfs_tmpfile(dentry, mode, 0);
+	struct dentry *ret = vfs_tmpfile(&init_user_ns, dentry, mode, 0);
 	int err = PTR_ERR_OR_ZERO(ret);
 
 	pr_debug("tmpfile(%pd2, 0%o) = %i\n", dentry, mode, err);
@@ -436,10 +445,12 @@ int ovl_set_nlink_lower(struct dentry *dentry);
 unsigned int ovl_get_nlink(struct ovl_fs *ofs, struct dentry *lowerdentry,
 			   struct dentry *upperdentry,
 			   unsigned int fallback);
-int ovl_setattr(struct dentry *dentry, struct iattr *attr);
-int ovl_getattr(const struct path *path, struct kstat *stat,
-		u32 request_mask, unsigned int flags);
-int ovl_permission(struct inode *inode, int mask);
+int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct iattr *attr);
+int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
+		struct kstat *stat, u32 request_mask, unsigned int flags);
+int ovl_permission(struct user_namespace *mnt_userns, struct inode *inode,
+		   int mask);
 int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
 		  const void *value, size_t size, int flags);
 int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index d58b8f2bf9d0..fdd72f1a9c5e 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -803,17 +803,19 @@ retry:
 		 * allowed as upper are limited to "normal" ones, where checking
 		 * for the above two errors is sufficient.
 		 */
-		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
+		err = vfs_removexattr(&init_user_ns, work,
+				      XATTR_NAME_POSIX_ACL_DEFAULT);
 		if (err && err != -ENODATA && err != -EOPNOTSUPP)
 			goto out_dput;
 
-		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
+		err = vfs_removexattr(&init_user_ns, work,
+				      XATTR_NAME_POSIX_ACL_ACCESS);
 		if (err && err != -ENODATA && err != -EOPNOTSUPP)
 			goto out_dput;
 
 		/* Clear any inherited mode bits */
 		inode_lock(work->d_inode);
-		err = notify_change(work, &attr, NULL);
+		err = notify_change(&init_user_ns, work, &attr, NULL);
 		inode_unlock(work->d_inode);
 		if (err)
 			goto out_dput;
@@ -865,6 +867,10 @@ static int ovl_mount_dir_noesc(const char *name, struct path *path)
 		pr_err("filesystem on '%s' not supported\n", name);
 		goto out_put;
 	}
+	if (mnt_user_ns(path->mnt) != &init_user_ns) {
+		pr_err("idmapped layers are currently not supported\n");
+		goto out_put;
+	}
 	if (!d_is_dir(path->dentry)) {
 		pr_err("'%s' not a directory\n", name);
 		goto out_put;
@@ -989,6 +995,7 @@ ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 
 static int __maybe_unused
 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
+			struct user_namespace *mnt_userns,
 			struct dentry *dentry, struct inode *inode,
 			const char *name, const void *value,
 			size_t size, int flags)
@@ -1014,7 +1021,7 @@ ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 		goto out_acl_release;
 	}
 	err = -EPERM;
-	if (!inode_owner_or_capable(inode))
+	if (!inode_owner_or_capable(&init_user_ns, inode))
 		goto out_acl_release;
 
 	posix_acl_release(acl);
@@ -1026,10 +1033,10 @@ ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 	if (unlikely(inode->i_mode & S_ISGID) &&
 	    handler->flags == ACL_TYPE_ACCESS &&
 	    !in_group_p(inode->i_gid) &&
-	    !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
+	    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID)) {
 		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
 
-		err = ovl_setattr(dentry, &iattr);
+		err = ovl_setattr(&init_user_ns, dentry, &iattr);
 		if (err)
 			return err;
 	}
@@ -1053,6 +1060,7 @@ static int ovl_own_xattr_get(const struct xattr_handler *handler,
 }
 
 static int ovl_own_xattr_set(const struct xattr_handler *handler,
+			     struct user_namespace *mnt_userns,
 			     struct dentry *dentry, struct inode *inode,
 			     const char *name, const void *value,
 			     size_t size, int flags)
@@ -1068,6 +1076,7 @@ static int ovl_other_xattr_get(const struct xattr_handler *handler,
 }
 
 static int ovl_other_xattr_set(const struct xattr_handler *handler,
+			       struct user_namespace *mnt_userns,
 			       struct dentry *dentry, struct inode *inode,
 			       const char *name, const void *value,
 			       size_t size, int flags)
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 9826b003f1d2..7f5a01a11f97 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -479,12 +479,12 @@ struct file *ovl_path_open(struct path *path, int flags)
 		BUG();
 	}
 
-	err = inode_permission(inode, acc_mode | MAY_OPEN);
+	err = inode_permission(&init_user_ns, inode, acc_mode | MAY_OPEN);
 	if (err)
 		return ERR_PTR(err);
 
 	/* O_NOATIME is an optimization, don't fail if not permitted */
-	if (inode_owner_or_capable(inode))
+	if (inode_owner_or_capable(&init_user_ns, inode))
 		flags |= O_NOATIME;
 
 	return dentry_open(path, flags, current_cred());