fs: port i_{g,u}id_{needs_}update() 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, 16 insertions, 8 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 696540a86183..3611d459bf88 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1647,7 +1647,7 @@ static inline vfsuid_t i_uid_into_vfsuid(struct user_namespace *mnt_userns,
 
 /**
  * i_uid_needs_update - check whether inode's i_uid needs to be updated
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @attr: the new attributes of @inode
  * @inode: the inode to update
  *
@@ -1656,10 +1656,12 @@ static inline vfsuid_t i_uid_into_vfsuid(struct user_namespace *mnt_userns,
  *
  * Return: true if @inode's i_uid field needs to be updated, false if not.
  */
-static inline bool i_uid_needs_update(struct user_namespace *mnt_userns,
+static inline bool i_uid_needs_update(struct mnt_idmap *idmap,
 				      const struct iattr *attr,
 				      const struct inode *inode)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
 	return ((attr->ia_valid & ATTR_UID) &&
 		!vfsuid_eq(attr->ia_vfsuid,
 			   i_uid_into_vfsuid(mnt_userns, inode)));
@@ -1667,17 +1669,19 @@ static inline bool i_uid_needs_update(struct user_namespace *mnt_userns,
 
 /**
  * i_uid_update - update @inode's i_uid field
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @attr: the new attributes of @inode
  * @inode: the inode to update
  *
  * Safely update @inode's i_uid field translating the vfsuid of any idmapped
  * mount into the filesystem kuid.
  */
-static inline void i_uid_update(struct user_namespace *mnt_userns,
+static inline void i_uid_update(struct mnt_idmap *idmap,
 				const struct iattr *attr,
 				struct inode *inode)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
 	if (attr->ia_valid & ATTR_UID)
 		inode->i_uid = from_vfsuid(mnt_userns, i_user_ns(inode),
 					   attr->ia_vfsuid);
@@ -1699,7 +1703,7 @@ static inline vfsgid_t i_gid_into_vfsgid(struct user_namespace *mnt_userns,
 
 /**
  * i_gid_needs_update - check whether inode's i_gid needs to be updated
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @attr: the new attributes of @inode
  * @inode: the inode to update
  *
@@ -1708,10 +1712,12 @@ static inline vfsgid_t i_gid_into_vfsgid(struct user_namespace *mnt_userns,
  *
  * Return: true if @inode's i_gid field needs to be updated, false if not.
  */
-static inline bool i_gid_needs_update(struct user_namespace *mnt_userns,
+static inline bool i_gid_needs_update(struct mnt_idmap *idmap,
 				      const struct iattr *attr,
 				      const struct inode *inode)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
 	return ((attr->ia_valid & ATTR_GID) &&
 		!vfsgid_eq(attr->ia_vfsgid,
 			   i_gid_into_vfsgid(mnt_userns, inode)));
@@ -1719,17 +1725,19 @@ static inline bool i_gid_needs_update(struct user_namespace *mnt_userns,
 
 /**
  * i_gid_update - update @inode's i_gid field
- * @mnt_userns: user namespace of the mount the inode was found from
+ * @idmap: idmap of the mount the inode was found from
  * @attr: the new attributes of @inode
  * @inode: the inode to update
  *
  * Safely update @inode's i_gid field translating the vfsgid of any idmapped
  * mount into the filesystem kgid.
  */
-static inline void i_gid_update(struct user_namespace *mnt_userns,
+static inline void i_gid_update(struct mnt_idmap *idmap,
 				const struct iattr *attr,
 				struct inode *inode)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
 	if (attr->ia_valid & ATTR_GID)
 		inode->i_gid = from_vfsgid(mnt_userns, i_user_ns(inode),
 					   attr->ia_vfsgid);