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
  ...

6 files changed, 30 insertions, 29 deletions

diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c
index ad670369955f6..3d192b80a5619 100644
--- a/fs/fuse/acl.c
+++ b/fs/fuse/acl.c
@@ -12,7 +12,7 @@
 #include <linux/posix_acl_xattr.h>
 
 static struct posix_acl *__fuse_get_acl(struct fuse_conn *fc,
-					struct user_namespace *mnt_userns,
+					struct mnt_idmap *idmap,
 					struct inode *inode, int type, bool rcu)
 {
 	int size;
@@ -65,7 +65,7 @@ static inline bool fuse_no_acl(const struct fuse_conn *fc,
 	return !fc->posix_acl && (i_user_ns(inode) != &init_user_ns);
 }
 
-struct posix_acl *fuse_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *fuse_get_acl(struct mnt_idmap *idmap,
 			       struct dentry *dentry, int type)
 {
 	struct inode *inode = d_inode(dentry);
@@ -74,7 +74,7 @@ struct posix_acl *fuse_get_acl(struct user_namespace *mnt_userns,
 	if (fuse_no_acl(fc, inode))
 		return ERR_PTR(-EOPNOTSUPP);
 
-	return __fuse_get_acl(fc, mnt_userns, inode, type, false);
+	return __fuse_get_acl(fc, idmap, inode, type, false);
 }
 
 struct posix_acl *fuse_get_inode_acl(struct inode *inode, int type, bool rcu)
@@ -91,10 +91,10 @@ struct posix_acl *fuse_get_inode_acl(struct inode *inode, int type, bool rcu)
 	if (!fc->posix_acl)
 		return NULL;
 
-	return __fuse_get_acl(fc, &init_user_ns, inode, type, rcu);
+	return __fuse_get_acl(fc, &nop_mnt_idmap, inode, type, rcu);
 }
 
-int fuse_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+int fuse_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 		 struct posix_acl *acl, int type)
 {
 	struct inode *inode = d_inode(dentry);
@@ -146,8 +146,8 @@ int fuse_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 		 * be stripped.
 		 */
 		if (fc->posix_acl &&
-		    !vfsgid_in_group_p(i_gid_into_vfsgid(&init_user_ns, inode)) &&
-		    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID))
+		    !vfsgid_in_group_p(i_gid_into_vfsgid(&nop_mnt_idmap, inode)) &&
+		    !capable_wrt_inode_uidgid(&nop_mnt_idmap, inode, CAP_FSETID))
 			extra_flags |= FUSE_SETXATTR_ACL_KILL_SGID;
 
 		ret = fuse_setxattr(inode, name, value, size, 0, extra_flags);
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 2725fb54328e5..cd1eae61e84c6 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -645,7 +645,7 @@ out_err:
 	return err;
 }
 
-static int fuse_mknod(struct user_namespace *, struct inode *, struct dentry *,
+static int fuse_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
 		      umode_t, dev_t);
 static int fuse_atomic_open(struct inode *dir, struct dentry *entry,
 			    struct file *file, unsigned flags,
@@ -686,7 +686,7 @@ out_dput:
 	return err;
 
 mknod:
-	err = fuse_mknod(&init_user_ns, dir, entry, mode, 0);
+	err = fuse_mknod(&nop_mnt_idmap, dir, entry, mode, 0);
 	if (err)
 		goto out_dput;
 no_open:
@@ -773,7 +773,7 @@ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args,
 	return err;
 }
 
-static int fuse_mknod(struct user_namespace *mnt_userns, struct inode *dir,
+static int fuse_mknod(struct mnt_idmap *idmap, struct inode *dir,
 		      struct dentry *entry, umode_t mode, dev_t rdev)
 {
 	struct fuse_mknod_in inarg;
@@ -796,13 +796,13 @@ static int fuse_mknod(struct user_namespace *mnt_userns, struct inode *dir,
 	return create_new_entry(fm, &args, dir, entry, mode);
 }
 
-static int fuse_create(struct user_namespace *mnt_userns, struct inode *dir,
+static int fuse_create(struct mnt_idmap *idmap, struct inode *dir,
 		       struct dentry *entry, umode_t mode, bool excl)
 {
-	return fuse_mknod(&init_user_ns, dir, entry, mode, 0);
+	return fuse_mknod(&nop_mnt_idmap, dir, entry, mode, 0);
 }
 
-static int fuse_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
+static int fuse_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
 			struct file *file, umode_t mode)
 {
 	struct fuse_conn *fc = get_fuse_conn(dir);
@@ -819,7 +819,7 @@ static int fuse_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
 	return err;
 }
 
-static int fuse_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+static int fuse_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 		      struct dentry *entry, umode_t mode)
 {
 	struct fuse_mkdir_in inarg;
@@ -841,7 +841,7 @@ static int fuse_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 	return create_new_entry(fm, &args, dir, entry, S_IFDIR);
 }
 
-static int fuse_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+static int fuse_symlink(struct mnt_idmap *idmap, struct inode *dir,
 			struct dentry *entry, const char *link)
 {
 	struct fuse_mount *fm = get_fuse_mount(dir);
@@ -998,7 +998,7 @@ static int fuse_rename_common(struct inode *olddir, struct dentry *oldent,
 	return err;
 }
 
-static int fuse_rename2(struct user_namespace *mnt_userns, struct inode *olddir,
+static int fuse_rename2(struct mnt_idmap *idmap, struct inode *olddir,
 			struct dentry *oldent, struct inode *newdir,
 			struct dentry *newent, unsigned int flags)
 {
@@ -1156,7 +1156,7 @@ static int fuse_update_get_attr(struct inode *inode, struct file *file,
 		forget_all_cached_acls(inode);
 		err = fuse_do_getattr(inode, stat, file);
 	} else if (stat) {
-		generic_fillattr(&init_user_ns, inode, stat);
+		generic_fillattr(&nop_mnt_idmap, inode, stat);
 		stat->mode = fi->orig_i_mode;
 		stat->ino = fi->orig_ino;
 	}
@@ -1326,7 +1326,7 @@ static int fuse_perm_getattr(struct inode *inode, int mask)
  * access request is sent.  Execute permission is still checked
  * locally based on file mode.
  */
-static int fuse_permission(struct user_namespace *mnt_userns,
+static int fuse_permission(struct mnt_idmap *idmap,
 			   struct inode *inode, int mask)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
@@ -1358,7 +1358,7 @@ static int fuse_permission(struct user_namespace *mnt_userns,
 	}
 
 	if (fc->default_permissions) {
-		err = generic_permission(&init_user_ns, inode, mask);
+		err = generic_permission(&nop_mnt_idmap, inode, mask);
 
 		/* If permission is denied, try to refresh file
 		   attributes.  This is also needed, because the root
@@ -1366,7 +1366,7 @@ static int fuse_permission(struct user_namespace *mnt_userns,
 		if (err == -EACCES && !refreshed) {
 			err = fuse_perm_getattr(inode, mask);
 			if (!err)
-				err = generic_permission(&init_user_ns,
+				err = generic_permission(&nop_mnt_idmap,
 							 inode, mask);
 		}
 
@@ -1690,7 +1690,7 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
 	if (!fc->default_permissions)
 		attr->ia_valid |= ATTR_FORCE;
 
-	err = setattr_prepare(&init_user_ns, dentry, attr);
+	err = setattr_prepare(&nop_mnt_idmap, dentry, attr);
 	if (err)
 		return err;
 
@@ -1837,7 +1837,7 @@ error:
 	return err;
 }
 
-static int fuse_setattr(struct user_namespace *mnt_userns, struct dentry *entry,
+static int fuse_setattr(struct mnt_idmap *idmap, struct dentry *entry,
 			struct iattr *attr)
 {
 	struct inode *inode = d_inode(entry);
@@ -1900,7 +1900,7 @@ static int fuse_setattr(struct user_namespace *mnt_userns, struct dentry *entry,
 	return ret;
 }
 
-static int fuse_getattr(struct user_namespace *mnt_userns,
+static int fuse_getattr(struct mnt_idmap *idmap,
 			const struct path *path, struct kstat *stat,
 			u32 request_mask, unsigned int flags)
 {
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 1458412f24923..82710d103556b 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1314,7 +1314,8 @@ static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			return err;
 
 		if (fc->handle_killpriv_v2 &&
-		    setattr_should_drop_suidgid(&init_user_ns, file_inode(file))) {
+		    setattr_should_drop_suidgid(&nop_mnt_idmap,
+						file_inode(file))) {
 			goto writethrough;
 		}
 
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 46797a171a84f..9b5058cf5bc32 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1267,9 +1267,9 @@ extern const struct xattr_handler *fuse_xattr_handlers[];
 
 struct posix_acl;
 struct posix_acl *fuse_get_inode_acl(struct inode *inode, int type, bool rcu);
-struct posix_acl *fuse_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *fuse_get_acl(struct mnt_idmap *idmap,
 			       struct dentry *dentry, int type);
-int fuse_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+int fuse_set_acl(struct mnt_idmap *, struct dentry *dentry,
 		 struct posix_acl *acl, int type);
 
 /* readdir.c */
@@ -1309,7 +1309,7 @@ long fuse_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
 long fuse_file_compat_ioctl(struct file *file, unsigned int cmd,
 			    unsigned long arg);
 int fuse_fileattr_get(struct dentry *dentry, struct fileattr *fa);
-int fuse_fileattr_set(struct user_namespace *mnt_userns,
+int fuse_fileattr_set(struct mnt_idmap *idmap,
 		      struct dentry *dentry, struct fileattr *fa);
 
 /* file.c */
diff --git a/fs/fuse/ioctl.c b/fs/fuse/ioctl.c
index fcce94ace2c23..e50a18ee6cc65 100644
--- a/fs/fuse/ioctl.c
+++ b/fs/fuse/ioctl.c
@@ -467,7 +467,7 @@ cleanup:
 	return err;
 }
 
-int fuse_fileattr_set(struct user_namespace *mnt_userns,
+int fuse_fileattr_set(struct mnt_idmap *idmap,
 		      struct dentry *dentry, struct fileattr *fa)
 {
 	struct inode *inode = d_inode(dentry);
diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c
index 9fe571ab569ed..49c01559580f4 100644
--- a/fs/fuse/xattr.c
+++ b/fs/fuse/xattr.c
@@ -189,7 +189,7 @@ static int fuse_xattr_get(const struct xattr_handler *handler,
 }
 
 static int fuse_xattr_set(const struct xattr_handler *handler,
-			  struct user_namespace *mnt_userns,
+			  struct mnt_idmap *idmap,
 			  struct dentry *dentry, struct inode *inode,
 			  const char *name, const void *value, size_t size,
 			  int flags)