fs: port vfs{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>

2 files changed, 24 insertions, 30 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 54a95ed68322..bd040fe31014 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1642,8 +1642,7 @@ static inline void i_gid_write(struct inode *inode, gid_t gid)
 static inline vfsuid_t i_uid_into_vfsuid(struct mnt_idmap *idmap,
 					 const struct inode *inode)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-	return make_vfsuid(mnt_userns, i_user_ns(inode), inode->i_uid);
+	return make_vfsuid(idmap, i_user_ns(inode), inode->i_uid);
 }
 
 /**
@@ -1679,10 +1678,8 @@ 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),
+		inode->i_uid = from_vfsuid(idmap, i_user_ns(inode),
 					   attr->ia_vfsuid);
 }
 
@@ -1697,8 +1694,7 @@ static inline void i_uid_update(struct mnt_idmap *idmap,
 static inline vfsgid_t i_gid_into_vfsgid(struct mnt_idmap *idmap,
 					 const struct inode *inode)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-	return make_vfsgid(mnt_userns, i_user_ns(inode), inode->i_gid);
+	return make_vfsgid(idmap, i_user_ns(inode), inode->i_gid);
 }
 
 /**
@@ -1734,10 +1730,8 @@ 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),
+		inode->i_gid = from_vfsgid(idmap, i_user_ns(inode),
 					   attr->ia_vfsgid);
 }
 
diff --git a/include/linux/mnt_idmapping.h b/include/linux/mnt_idmapping.h
index d63e7c84a389..53d42b0b6f17 100644
--- a/include/linux/mnt_idmapping.h
+++ b/include/linux/mnt_idmapping.h
@@ -170,7 +170,7 @@ static inline bool no_idmapping(const struct user_namespace *mnt_userns,
 
 /**
  * make_vfsuid - map a filesystem kuid into a mnt_userns
- * @mnt_userns: the mount's idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @kuid : kuid to be mapped
  *
@@ -189,11 +189,12 @@ static inline bool no_idmapping(const struct user_namespace *mnt_userns,
  * returned.
  */
 
-static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
+static inline vfsuid_t make_vfsuid(struct mnt_idmap *idmap,
 				   struct user_namespace *fs_userns,
 				   kuid_t kuid)
 {
 	uid_t uid;
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 
 	if (no_idmapping(mnt_userns, fs_userns))
 		return VFSUIDT_INIT(kuid);
@@ -208,7 +209,7 @@ static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
 
 /**
  * make_vfsgid - map a filesystem kgid into a mnt_userns
- * @mnt_userns: the mount's idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @kgid : kgid to be mapped
  *
@@ -227,11 +228,12 @@ static inline vfsuid_t make_vfsuid(struct user_namespace *mnt_userns,
  * returned.
  */
 
-static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
+static inline vfsgid_t make_vfsgid(struct mnt_idmap *idmap,
 				   struct user_namespace *fs_userns,
 				   kgid_t kgid)
 {
 	gid_t gid;
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 
 	if (no_idmapping(mnt_userns, fs_userns))
 		return VFSGIDT_INIT(kgid);
@@ -246,7 +248,7 @@ static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
 
 /**
  * from_vfsuid - map a vfsuid into the filesystem idmapping
- * @mnt_userns: the mount's idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsuid : vfsuid to be mapped
  *
@@ -255,11 +257,12 @@ static inline vfsgid_t make_vfsgid(struct user_namespace *mnt_userns,
  *
  * Return: @vfsuid mapped into the filesystem idmapping
  */
-static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
+static inline kuid_t from_vfsuid(struct mnt_idmap *idmap,
 				 struct user_namespace *fs_userns,
 				 vfsuid_t vfsuid)
 {
 	uid_t uid;
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 
 	if (no_idmapping(mnt_userns, fs_userns))
 		return AS_KUIDT(vfsuid);
@@ -273,7 +276,7 @@ static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
 
 /**
  * vfsuid_has_fsmapping - check whether a vfsuid maps into the filesystem
- * @mnt_userns: the mount's idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsuid: vfsuid to be mapped
  *
@@ -283,11 +286,11 @@ static inline kuid_t from_vfsuid(struct user_namespace *mnt_userns,
  *
  * Return: true if @vfsuid has a mapping in the filesystem, false if not.
  */
-static inline bool vfsuid_has_fsmapping(struct user_namespace *mnt_userns,
+static inline bool vfsuid_has_fsmapping(struct mnt_idmap *idmap,
 					struct user_namespace *fs_userns,
 					vfsuid_t vfsuid)
 {
-	return uid_valid(from_vfsuid(mnt_userns, fs_userns, vfsuid));
+	return uid_valid(from_vfsuid(idmap, fs_userns, vfsuid));
 }
 
 static inline bool vfsuid_has_mapping(struct user_namespace *userns,
@@ -311,7 +314,7 @@ static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
 
 /**
  * from_vfsgid - map a vfsgid into the filesystem idmapping
- * @mnt_userns: the mount's idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsgid : vfsgid to be mapped
  *
@@ -320,11 +323,12 @@ static inline kuid_t vfsuid_into_kuid(vfsuid_t vfsuid)
  *
  * Return: @vfsgid mapped into the filesystem idmapping
  */
-static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
+static inline kgid_t from_vfsgid(struct mnt_idmap *idmap,
 				 struct user_namespace *fs_userns,
 				 vfsgid_t vfsgid)
 {
 	gid_t gid;
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 
 	if (no_idmapping(mnt_userns, fs_userns))
 		return AS_KGIDT(vfsgid);
@@ -338,7 +342,7 @@ static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
 
 /**
  * vfsgid_has_fsmapping - check whether a vfsgid maps into the filesystem
- * @mnt_userns: the mount's idmapping
+ * @idmap: the mount's idmapping
  * @fs_userns: the filesystem's idmapping
  * @vfsgid: vfsgid to be mapped
  *
@@ -348,11 +352,11 @@ static inline kgid_t from_vfsgid(struct user_namespace *mnt_userns,
  *
  * Return: true if @vfsgid has a mapping in the filesystem, false if not.
  */
-static inline bool vfsgid_has_fsmapping(struct user_namespace *mnt_userns,
+static inline bool vfsgid_has_fsmapping(struct mnt_idmap *idmap,
 					struct user_namespace *fs_userns,
 					vfsgid_t vfsgid)
 {
-	return gid_valid(from_vfsgid(mnt_userns, fs_userns, vfsgid));
+	return gid_valid(from_vfsgid(idmap, fs_userns, vfsgid));
 }
 
 static inline bool vfsgid_has_mapping(struct user_namespace *userns,
@@ -390,9 +394,7 @@ static inline kgid_t vfsgid_into_kgid(vfsgid_t vfsgid)
 static inline kuid_t mapped_fsuid(struct mnt_idmap *idmap,
 				  struct user_namespace *fs_userns)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-	return from_vfsuid(mnt_userns, fs_userns,
-			   VFSUIDT_INIT(current_fsuid()));
+	return from_vfsuid(idmap, fs_userns, VFSUIDT_INIT(current_fsuid()));
 }
 
 /**
@@ -411,9 +413,7 @@ static inline kuid_t mapped_fsuid(struct mnt_idmap *idmap,
 static inline kgid_t mapped_fsgid(struct mnt_idmap *idmap,
 				  struct user_namespace *fs_userns)
 {
-	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
-	return from_vfsgid(mnt_userns, fs_userns,
-			   VFSGIDT_INIT(current_fsgid()));
+	return from_vfsgid(idmap, fs_userns, VFSGIDT_INIT(current_fsgid()));
 }
 
 #endif /* _LINUX_MNT_IDMAPPING_H */