fs: port fs{g,u}id helpers to mnt_idmap

Convert to struct mnt_idmap.

Last cycle we merged the necessary infrastructure in
256c8aed2b42 ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to 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 relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.

Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.

Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

1 files changed, 10 insertions, 11 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 173c5274a63aa..54a95ed68322c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1744,29 +1744,29 @@ static inline void i_gid_update(struct mnt_idmap *idmap,
 /**
  * inode_fsuid_set - initialize inode's i_uid field with callers fsuid
  * @inode: inode to initialize
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  *
  * Initialize the i_uid field of @inode. If the inode was found/created via
- * an idmapped mount map the caller's fsuid according to @mnt_users.
+ * an idmapped mount map the caller's fsuid according to @idmap.
  */
 static inline void inode_fsuid_set(struct inode *inode,
-				   struct user_namespace *mnt_userns)
+				   struct mnt_idmap *idmap)
 {
-	inode->i_uid = mapped_fsuid(mnt_userns, i_user_ns(inode));
+	inode->i_uid = mapped_fsuid(idmap, i_user_ns(inode));
 }
 
 /**
  * inode_fsgid_set - initialize inode's i_gid field with callers fsgid
  * @inode: inode to initialize
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  *
  * Initialize the i_gid field of @inode. If the inode was found/created via
- * an idmapped mount map the caller's fsgid according to @mnt_users.
+ * an idmapped mount map the caller's fsgid according to @idmap.
  */
 static inline void inode_fsgid_set(struct inode *inode,
-				   struct user_namespace *mnt_userns)
+				   struct mnt_idmap *idmap)
 {
-	inode->i_gid = mapped_fsgid(mnt_userns, i_user_ns(inode));
+	inode->i_gid = mapped_fsgid(idmap, i_user_ns(inode));
 }
 
 /**
@@ -1784,14 +1784,13 @@ static inline bool fsuidgid_has_mapping(struct super_block *sb,
 					struct mnt_idmap *idmap)
 {
 	struct user_namespace *fs_userns = sb->s_user_ns;
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	kuid_t kuid;
 	kgid_t kgid;
 
-	kuid = mapped_fsuid(mnt_userns, fs_userns);
+	kuid = mapped_fsuid(idmap, fs_userns);
 	if (!uid_valid(kuid))
 		return false;
-	kgid = mapped_fsgid(mnt_userns, fs_userns);
+	kgid = mapped_fsgid(idmap, fs_userns);
 	if (!gid_valid(kgid))
 		return false;
 	return kuid_has_mapping(fs_userns, kuid) &&