Merge tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping

Pull vfs idmapping updates from Christian Brauner:

 - Last cycle we introduced the dedicated struct mnt_idmap type for
   mount idmapping and the required infrastucture in 256c8aed2b42 ("fs:
   introduce dedicated idmap type for mounts"). As promised in last
   cycle's pull request message this converts everything to rely on
   struct mnt_idmap.

   Currently we still pass around the plain namespace that was attached
   to a mount. This is in general pretty convenient but it makes it easy
   to conflate namespaces that are relevant on the filesystem with
   namespaces that are relevant on the mount level. Especially for
   non-vfs developers without detailed knowledge in this area this was a
   potential source for bugs.

   This finishes the conversion. Instead of passing the plain namespace
   around this updates all places that currently take a pointer to a
   mnt_userns with a pointer to struct mnt_idmap.

   Now that the conversion is done all helpers down to the really
   low-level helpers only accept a struct mnt_idmap argument instead of
   two namespace arguments.

   Conflating mount and other idmappings will now cause the compiler to
   complain loudly thus eliminating the possibility of any bugs. This
   makes it impossible for filesystem developers to mix up mount and
   filesystem idmappings as they are two distinct types and require
   distinct helpers that cannot be used interchangeably.

   Everything associated with struct mnt_idmap is moved into a single
   separate file. With that change no code can poke around in struct
   mnt_idmap. It can only be interacted with through dedicated helpers.
   That means all filesystems are and all of the vfs is completely
   oblivious to the actual implementation of idmappings.

   We are now also able to extend struct mnt_idmap as we see fit. For
   example, we can decouple it completely from namespaces for users that
   don't require or don't want to use them at all. We can also extend
   the concept of idmappings so we can cover filesystem specific
   requirements.

   In combination with the vfs{g,u}id_t work we finished in v6.2 this
   makes this feature substantially more robust and thus difficult to
   implement wrong by a given filesystem and also protects the vfs.

 - Enable idmapped mounts for tmpfs and fulfill a longstanding request.

   A long-standing request from users had been to make it possible to
   create idmapped mounts for tmpfs. For example, to share the host's
   tmpfs mount between multiple sandboxes. This is a prerequisite for
   some advanced Kubernetes cases. Systemd also has a range of use-cases
   to increase service isolation. And there are more users of this.

   However, with all of the other work going on this was way down on the
   priority list but luckily someone other than ourselves picked this
   up.

   As usual the patch is tiny as all the infrastructure work had been
   done multiple kernel releases ago. In addition to all the tests that
   we already have I requested that Rodrigo add a dedicated tmpfs
   testsuite for idmapped mounts to xfstests. It is to be included into
   xfstests during the v6.3 development cycle. This should add a slew of
   additional tests.

* tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping: (26 commits)
  shmem: support idmapped mounts for tmpfs
  fs: move mnt_idmap
  fs: port vfs{g,u}id helpers to mnt_idmap
  fs: port fs{g,u}id helpers to mnt_idmap
  fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap
  fs: port i_{g,u}id_{needs_}update() to mnt_idmap
  quota: port to mnt_idmap
  fs: port privilege checking helpers to mnt_idmap
  fs: port inode_owner_or_capable() to mnt_idmap
  fs: port inode_init_owner() to mnt_idmap
  fs: port acl to mnt_idmap
  fs: port xattr to mnt_idmap
  fs: port ->permission() to pass mnt_idmap
  fs: port ->fileattr_set() to pass mnt_idmap
  fs: port ->set_acl() to pass mnt_idmap
  fs: port ->get_acl() to pass mnt_idmap
  fs: port ->tmpfile() to pass mnt_idmap
  fs: port ->rename() to pass mnt_idmap
  fs: port ->mknod() to pass mnt_idmap
  fs: port ->mkdir() to pass mnt_idmap
  ...

4 files changed, 8 insertions, 8 deletions

diff --git a/fs/hfs/attr.c b/fs/hfs/attr.c
index 2bd54efaf416..6341bb248247 100644
--- a/fs/hfs/attr.c
+++ b/fs/hfs/attr.c
@@ -121,7 +121,7 @@ static int hfs_xattr_get(const struct xattr_handler *handler,
 }
 
 static int hfs_xattr_set(const struct xattr_handler *handler,
-			 struct user_namespace *mnt_userns,
+			 struct mnt_idmap *idmap,
 			 struct dentry *unused, struct inode *inode,
 			 const char *name, const void *value, size_t size,
 			 int flags)
diff --git a/fs/hfs/dir.c b/fs/hfs/dir.c
index 527f6e46cbe8..3e1e3dcf0b48 100644
--- a/fs/hfs/dir.c
+++ b/fs/hfs/dir.c
@@ -189,7 +189,7 @@ static int hfs_dir_release(struct inode *inode, struct file *file)
  * a directory and return a corresponding inode, given the inode for
  * the directory and the name (and its length) of the new file.
  */
-static int hfs_create(struct user_namespace *mnt_userns, struct inode *dir,
+static int hfs_create(struct mnt_idmap *idmap, struct inode *dir,
 		      struct dentry *dentry, umode_t mode, bool excl)
 {
 	struct inode *inode;
@@ -219,7 +219,7 @@ static int hfs_create(struct user_namespace *mnt_userns, struct inode *dir,
  * in a directory, given the inode for the parent directory and the
  * name (and its length) of the new directory.
  */
-static int hfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+static int hfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 		     struct dentry *dentry, umode_t mode)
 {
 	struct inode *inode;
@@ -280,7 +280,7 @@ static int hfs_remove(struct inode *dir, struct dentry *dentry)
  * new file/directory.
  * XXX: how do you handle must_be dir?
  */
-static int hfs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
+static int hfs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 		      struct dentry *old_dentry, struct inode *new_dir,
 		      struct dentry *new_dentry, unsigned int flags)
 {
diff --git a/fs/hfs/hfs_fs.h b/fs/hfs/hfs_fs.h
index 68d0305880f7..49d02524e667 100644
--- a/fs/hfs/hfs_fs.h
+++ b/fs/hfs/hfs_fs.h
@@ -206,7 +206,7 @@ int hfs_write_begin(struct file *file, struct address_space *mapping,
 extern struct inode *hfs_new_inode(struct inode *, const struct qstr *, umode_t);
 extern void hfs_inode_write_fork(struct inode *, struct hfs_extent *, __be32 *, __be32 *);
 extern int hfs_write_inode(struct inode *, struct writeback_control *);
-extern int hfs_inode_setattr(struct user_namespace *, struct dentry *,
+extern int hfs_inode_setattr(struct mnt_idmap *, struct dentry *,
 			     struct iattr *);
 extern void hfs_inode_read_fork(struct inode *inode, struct hfs_extent *ext,
 			__be32 log_size, __be32 phys_size, u32 clump_size);
diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c
index 3a155c1d810e..1f7bd068acf0 100644
--- a/fs/hfs/inode.c
+++ b/fs/hfs/inode.c
@@ -611,14 +611,14 @@ static int hfs_file_release(struct inode *inode, struct file *file)
  *     correspond to the same HFS file.
  */
 
-int hfs_inode_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
+int hfs_inode_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		      struct iattr *attr)
 {
 	struct inode *inode = d_inode(dentry);
 	struct hfs_sb_info *hsb = HFS_SB(inode->i_sb);
 	int error;
 
-	error = setattr_prepare(&init_user_ns, dentry,
+	error = setattr_prepare(&nop_mnt_idmap, dentry,
 				attr); /* basic permission checks */
 	if (error)
 		return error;
@@ -658,7 +658,7 @@ int hfs_inode_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 						  current_time(inode);
 	}
 
-	setattr_copy(&init_user_ns, inode, attr);
+	setattr_copy(&nop_mnt_idmap, inode, attr);
 	mark_inode_dirty(inode);
 	return 0;
 }