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, 43 insertions, 34 deletions

diff --git a/mm/madvise.c b/mm/madvise.c
index b6ea204d4e23..18c2e2affac4 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -329,7 +329,7 @@ static inline bool can_do_file_pageout(struct vm_area_struct *vma)
 	 * otherwise we'd be including shared non-exclusive mappings, which
 	 * opens a side channel.
 	 */
-	return inode_owner_or_capable(&init_user_ns,
+	return inode_owner_or_capable(&nop_mnt_idmap,
 				      file_inode(vma->vm_file)) ||
 	       file_permission(vma->vm_file, MAY_WRITE) == 0;
 }
diff --git a/mm/mincore.c b/mm/mincore.c
index a085a2aeabd8..cd69b9db0081 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -168,7 +168,7 @@ static inline bool can_do_mincore(struct vm_area_struct *vma)
 	 * for writing; otherwise we'd be including shared non-exclusive
 	 * mappings, which opens a side channel.
 	 */
-	return inode_owner_or_capable(&init_user_ns,
+	return inode_owner_or_capable(&nop_mnt_idmap,
 				      file_inode(vma->vm_file)) ||
 	       file_permission(vma->vm_file, MAY_WRITE) == 0;
 }
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 04c3ac9448a1..afcf46e99cda 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -162,7 +162,7 @@ const struct address_space_operations secretmem_aops = {
 	.migrate_folio	= secretmem_migrate_folio,
 };
 
-static int secretmem_setattr(struct user_namespace *mnt_userns,
+static int secretmem_setattr(struct mnt_idmap *idmap,
 			     struct dentry *dentry, struct iattr *iattr)
 {
 	struct inode *inode = d_inode(dentry);
@@ -175,7 +175,7 @@ static int secretmem_setattr(struct user_namespace *mnt_userns,
 	if ((ia_valid & ATTR_SIZE) && inode->i_size)
 		ret = -EINVAL;
 	else
-		ret = simple_setattr(mnt_userns, dentry, iattr);
+		ret = simple_setattr(idmap, dentry, iattr);
 
 	filemap_invalidate_unlock(mapping);
 
diff --git a/mm/shmem.c b/mm/shmem.c
index 0005ab2c29af..41f82c5a5e28 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1045,7 +1045,7 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 }
 EXPORT_SYMBOL_GPL(shmem_truncate_range);
 
-static int shmem_getattr(struct user_namespace *mnt_userns,
+static int shmem_getattr(struct mnt_idmap *idmap,
 			 const struct path *path, struct kstat *stat,
 			 u32 request_mask, unsigned int query_flags)
 {
@@ -1066,7 +1066,7 @@ static int shmem_getattr(struct user_namespace *mnt_userns,
 	stat->attributes_mask |= (STATX_ATTR_APPEND |
 			STATX_ATTR_IMMUTABLE |
 			STATX_ATTR_NODUMP);
-	generic_fillattr(&init_user_ns, inode, stat);
+	generic_fillattr(idmap, inode, stat);
 
 	if (shmem_is_huge(NULL, inode, 0, false))
 		stat->blksize = HPAGE_PMD_SIZE;
@@ -1080,7 +1080,7 @@ static int shmem_getattr(struct user_namespace *mnt_userns,
 	return 0;
 }
 
-static int shmem_setattr(struct user_namespace *mnt_userns,
+static int shmem_setattr(struct mnt_idmap *idmap,
 			 struct dentry *dentry, struct iattr *attr)
 {
 	struct inode *inode = d_inode(dentry);
@@ -1089,7 +1089,7 @@ static int shmem_setattr(struct user_namespace *mnt_userns,
 	bool update_mtime = false;
 	bool update_ctime = true;
 
-	error = setattr_prepare(&init_user_ns, dentry, attr);
+	error = setattr_prepare(idmap, dentry, attr);
 	if (error)
 		return error;
 
@@ -1127,9 +1127,9 @@ static int shmem_setattr(struct user_namespace *mnt_userns,
 		}
 	}
 
-	setattr_copy(&init_user_ns, inode, attr);
+	setattr_copy(idmap, inode, attr);
 	if (attr->ia_valid & ATTR_MODE)
-		error = posix_acl_chmod(&init_user_ns, dentry, inode->i_mode);
+		error = posix_acl_chmod(idmap, dentry, inode->i_mode);
 	if (!error && update_ctime) {
 		inode->i_ctime = current_time(inode);
 		if (update_mtime)
@@ -2327,8 +2327,9 @@ static void shmem_set_inode_flags(struct inode *inode, unsigned int fsflags)
 #define shmem_initxattrs NULL
 #endif
 
-static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
-				     umode_t mode, dev_t dev, unsigned long flags)
+static struct inode *shmem_get_inode(struct mnt_idmap *idmap, struct super_block *sb,
+				     struct inode *dir, umode_t mode, dev_t dev,
+				     unsigned long flags)
 {
 	struct inode *inode;
 	struct shmem_inode_info *info;
@@ -2341,7 +2342,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, struct inode *dir,
 	inode = new_inode(sb);
 	if (inode) {
 		inode->i_ino = ino;
-		inode_init_owner(&init_user_ns, inode, dir, mode);
+		inode_init_owner(idmap, inode, dir, mode);
 		inode->i_blocks = 0;
 		inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 		inode->i_generation = get_random_u32();
@@ -2913,13 +2914,13 @@ static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
  * File creation. Allocate an inode, and we're done..
  */
 static int
-shmem_mknod(struct user_namespace *mnt_userns, struct inode *dir,
+shmem_mknod(struct mnt_idmap *idmap, struct inode *dir,
 	    struct dentry *dentry, umode_t mode, dev_t dev)
 {
 	struct inode *inode;
 	int error = -ENOSPC;
 
-	inode = shmem_get_inode(dir->i_sb, dir, mode, dev, VM_NORESERVE);
+	inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, dev, VM_NORESERVE);
 	if (inode) {
 		error = simple_acl_create(dir, inode);
 		if (error)
@@ -2944,13 +2945,13 @@ out_iput:
 }
 
 static int
-shmem_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
+shmem_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
 	      struct file *file, umode_t mode)
 {
 	struct inode *inode;
 	int error = -ENOSPC;
 
-	inode = shmem_get_inode(dir->i_sb, dir, mode, 0, VM_NORESERVE);
+	inode = shmem_get_inode(idmap, dir->i_sb, dir, mode, 0, VM_NORESERVE);
 	if (inode) {
 		error = security_inode_init_security(inode, dir,
 						     NULL,
@@ -2968,22 +2969,22 @@ out_iput:
 	return error;
 }
 
-static int shmem_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
+static int shmem_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 		       struct dentry *dentry, umode_t mode)
 {
 	int error;
 
-	if ((error = shmem_mknod(&init_user_ns, dir, dentry,
-				 mode | S_IFDIR, 0)))
+	error = shmem_mknod(idmap, dir, dentry, mode | S_IFDIR, 0);
+	if (error)
 		return error;
 	inc_nlink(dir);
 	return 0;
 }
 
-static int shmem_create(struct user_namespace *mnt_userns, struct inode *dir,
+static int shmem_create(struct mnt_idmap *idmap, struct inode *dir,
 			struct dentry *dentry, umode_t mode, bool excl)
 {
-	return shmem_mknod(&init_user_ns, dir, dentry, mode | S_IFREG, 0);
+	return shmem_mknod(idmap, dir, dentry, mode | S_IFREG, 0);
 }
 
 /*
@@ -3043,7 +3044,7 @@ static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
 	return shmem_unlink(dir, dentry);
 }
 
-static int shmem_whiteout(struct user_namespace *mnt_userns,
+static int shmem_whiteout(struct mnt_idmap *idmap,
 			  struct inode *old_dir, struct dentry *old_dentry)
 {
 	struct dentry *whiteout;
@@ -3053,7 +3054,7 @@ static int shmem_whiteout(struct user_namespace *mnt_userns,
 	if (!whiteout)
 		return -ENOMEM;
 
-	error = shmem_mknod(&init_user_ns, old_dir, whiteout,
+	error = shmem_mknod(idmap, old_dir, whiteout,
 			    S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
 	dput(whiteout);
 	if (error)
@@ -3076,7 +3077,7 @@ static int shmem_whiteout(struct user_namespace *mnt_userns,
  * it exists so that the VFS layer correctly free's it when it
  * gets overwritten.
  */
-static int shmem_rename2(struct user_namespace *mnt_userns,
+static int shmem_rename2(struct mnt_idmap *idmap,
 			 struct inode *old_dir, struct dentry *old_dentry,
 			 struct inode *new_dir, struct dentry *new_dentry,
 			 unsigned int flags)
@@ -3096,7 +3097,7 @@ static int shmem_rename2(struct user_namespace *mnt_userns,
 	if (flags & RENAME_WHITEOUT) {
 		int error;
 
-		error = shmem_whiteout(&init_user_ns, old_dir, old_dentry);
+		error = shmem_whiteout(idmap, old_dir, old_dentry);
 		if (error)
 			return error;
 	}
@@ -3122,7 +3123,7 @@ static int shmem_rename2(struct user_namespace *mnt_userns,
 	return 0;
 }
 
-static int shmem_symlink(struct user_namespace *mnt_userns, struct inode *dir,
+static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
 			 struct dentry *dentry, const char *symname)
 {
 	int error;
@@ -3134,7 +3135,7 @@ static int shmem_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	if (len > PAGE_SIZE)
 		return -ENAMETOOLONG;
 
-	inode = shmem_get_inode(dir->i_sb, dir, S_IFLNK | 0777, 0,
+	inode = shmem_get_inode(idmap, dir->i_sb, dir, S_IFLNK | 0777, 0,
 				VM_NORESERVE);
 	if (!inode)
 		return -ENOSPC;
@@ -3227,7 +3228,7 @@ static int shmem_fileattr_get(struct dentry *dentry, struct fileattr *fa)
 	return 0;
 }
 
-static int shmem_fileattr_set(struct user_namespace *mnt_userns,
+static int shmem_fileattr_set(struct mnt_idmap *idmap,
 			      struct dentry *dentry, struct fileattr *fa)
 {
 	struct inode *inode = d_inode(dentry);
@@ -3301,7 +3302,7 @@ static int shmem_xattr_handler_get(const struct xattr_handler *handler,
 }
 
 static int shmem_xattr_handler_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)
@@ -3817,7 +3818,8 @@ static int shmem_fill_super(struct super_block *sb, struct fs_context *fc)
 #endif
 	uuid_gen(&sb->s_uuid);
 
-	inode = shmem_get_inode(sb, NULL, S_IFDIR | sbinfo->mode, 0, VM_NORESERVE);
+	inode = shmem_get_inode(&nop_mnt_idmap, sb, NULL, S_IFDIR | sbinfo->mode, 0,
+				VM_NORESERVE);
 	if (!inode)
 		goto failed;
 	inode->i_uid = sbinfo->uid;
@@ -4042,7 +4044,11 @@ static struct file_system_type shmem_fs_type = {
 	.parameters	= shmem_fs_parameters,
 #endif
 	.kill_sb	= kill_litter_super,
+#ifdef CONFIG_SHMEM
+	.fs_flags	= FS_USERNS_MOUNT | FS_ALLOW_IDMAP,
+#else
 	.fs_flags	= FS_USERNS_MOUNT,
+#endif
 };
 
 void __init shmem_init(void)
@@ -4194,7 +4200,7 @@ EXPORT_SYMBOL_GPL(shmem_truncate_range);
 #define shmem_vm_ops				generic_file_vm_ops
 #define shmem_anon_vm_ops			generic_file_vm_ops
 #define shmem_file_operations			ramfs_file_operations
-#define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
+#define shmem_get_inode(idmap, sb, dir, mode, dev, flags) ramfs_get_inode(sb, dir, mode, dev)
 #define shmem_acct_size(flags, size)		0
 #define shmem_unacct_size(flags, size)		do {} while (0)
 
@@ -4217,8 +4223,11 @@ static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name, l
 	if (shmem_acct_size(flags, size))
 		return ERR_PTR(-ENOMEM);
 
-	inode = shmem_get_inode(mnt->mnt_sb, NULL, S_IFREG | S_IRWXUGO, 0,
-				flags);
+	if (is_idmapped_mnt(mnt))
+		return ERR_PTR(-EINVAL);
+
+	inode = shmem_get_inode(&nop_mnt_idmap, mnt->mnt_sb, NULL,
+				S_IFREG | S_IRWXUGO, 0, flags);
 	if (unlikely(!inode)) {
 		shmem_unacct_size(flags, size);
 		return ERR_PTR(-ENOSPC);