fs: port privilege checking 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, 7 insertions, 7 deletions

diff --git a/include/linux/capability.h b/include/linux/capability.h
index 0a8ba82ef1af..03c2a613ad40 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -249,9 +249,9 @@ static inline bool ns_capable_setid(struct user_namespace *ns, int cap)
 }
 #endif /* CONFIG_MULTIUSER */
 bool privileged_wrt_inode_uidgid(struct user_namespace *ns,
-				 struct user_namespace *mnt_userns,
+				 struct mnt_idmap *idmap,
 				 const struct inode *inode);
-bool capable_wrt_inode_uidgid(struct user_namespace *mnt_userns,
+bool capable_wrt_inode_uidgid(struct mnt_idmap *idmap,
 			      const struct inode *inode, int cap);
 extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
 extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e6c76f308f5f..696540a86183 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2017,7 +2017,7 @@ extern long compat_ptr_ioctl(struct file *file, unsigned int cmd,
 void inode_init_owner(struct mnt_idmap *idmap, struct inode *inode,
 		      const struct inode *dir, umode_t mode);
 extern bool may_open_dev(const struct path *path);
-umode_t mode_strip_sgid(struct user_namespace *mnt_userns,
+umode_t mode_strip_sgid(struct mnt_idmap *idmap,
 			const struct inode *dir, umode_t mode);
 
 /*
@@ -2917,7 +2917,7 @@ static inline int path_permission(const struct path *path, int mask)
 	return inode_permission(mnt_idmap(path->mnt),
 				d_inode(path->dentry), mask);
 }
-int __check_sticky(struct user_namespace *mnt_userns, struct inode *dir,
+int __check_sticky(struct mnt_idmap *idmap, struct inode *dir,
 		   struct inode *inode);
 
 static inline bool execute_ok(struct inode *inode)
@@ -3105,7 +3105,7 @@ extern void __destroy_inode(struct inode *);
 extern struct inode *new_inode_pseudo(struct super_block *sb);
 extern struct inode *new_inode(struct super_block *sb);
 extern void free_inode_nonrcu(struct inode *inode);
-extern int setattr_should_drop_suidgid(struct user_namespace *, struct inode *);
+extern int setattr_should_drop_suidgid(struct mnt_idmap *, struct inode *);
 extern int file_remove_privs(struct file *);
 
 /*
@@ -3539,13 +3539,13 @@ static inline bool is_sxid(umode_t mode)
 	return mode & (S_ISUID | S_ISGID);
 }
 
-static inline int check_sticky(struct user_namespace *mnt_userns,
+static inline int check_sticky(struct mnt_idmap *idmap,
 			       struct inode *dir, struct inode *inode)
 {
 	if (!(dir->i_mode & S_ISVTX))
 		return 0;
 
-	return __check_sticky(mnt_userns, dir, inode);
+	return __check_sticky(idmap, dir, inode);
 }
 
 static inline void inode_has_no_xattr(struct inode *inode)