fs: port ->permission() to pass 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>

6 files changed, 28 insertions, 25 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 349f71650fa2..635ce7a7740f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1766,18 +1766,19 @@ static inline void inode_fsgid_set(struct inode *inode,
 /**
  * fsuidgid_has_mapping() - check whether caller's fsuid/fsgid is mapped
  * @sb: the superblock we want a mapping in
- * @mnt_userns: user namespace of the relevant mount
+ * @idmap: idmap of the relevant mount
  *
  * Check whether the caller's fsuid and fsgid have a valid mapping in the
  * s_user_ns of the superblock @sb. If the caller is on an idmapped mount map
- * the caller's fsuid and fsgid according to the @mnt_userns first.
+ * the caller's fsuid and fsgid according to the @idmap first.
  *
  * Return: true if fsuid and fsgid is mapped, false if not.
  */
 static inline bool fsuidgid_has_mapping(struct super_block *sb,
-					struct user_namespace *mnt_userns)
+					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;
 
@@ -2134,7 +2135,7 @@ struct file_operations {
 struct inode_operations {
 	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
 	const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
-	int (*permission) (struct user_namespace *, struct inode *, int);
+	int (*permission) (struct mnt_idmap *, struct inode *, int);
 	struct posix_acl * (*get_inode_acl)(struct inode *, int, bool);
 
 	int (*readlink) (struct dentry *, char __user *,int);
@@ -2322,9 +2323,11 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags
 #define IS_WHITEOUT(inode)	(S_ISCHR(inode->i_mode) && \
 				 (inode)->i_rdev == WHITEOUT_DEV)
 
-static inline bool HAS_UNMAPPED_ID(struct user_namespace *mnt_userns,
+static inline bool HAS_UNMAPPED_ID(struct mnt_idmap *idmap,
 				   struct inode *inode)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
 	return !vfsuid_valid(i_uid_into_vfsuid(mnt_userns, inode)) ||
 	       !vfsgid_valid(i_gid_into_vfsgid(mnt_userns, inode));
 }
@@ -2902,16 +2905,16 @@ static inline int bmap(struct inode *inode,  sector_t *block)
 
 int notify_change(struct mnt_idmap *, struct dentry *,
 		  struct iattr *, struct inode **);
-int inode_permission(struct user_namespace *, struct inode *, int);
-int generic_permission(struct user_namespace *, struct inode *, int);
+int inode_permission(struct mnt_idmap *, struct inode *, int);
+int generic_permission(struct mnt_idmap *, struct inode *, int);
 static inline int file_permission(struct file *file, int mask)
 {
-	return inode_permission(file_mnt_user_ns(file),
+	return inode_permission(file_mnt_idmap(file),
 				file_inode(file), mask);
 }
 static inline int path_permission(const struct path *path, int mask)
 {
-	return inode_permission(mnt_user_ns(path->mnt),
+	return inode_permission(mnt_idmap(path->mnt),
 				d_inode(path->dentry), mask);
 }
 int __check_sticky(struct user_namespace *mnt_userns, struct inode *dir,
@@ -3365,7 +3368,7 @@ extern int generic_check_addressable(unsigned, u64);
 
 extern void generic_set_encrypted_ci_d_ops(struct dentry *dentry);
 
-int may_setattr(struct user_namespace *mnt_userns, struct inode *inode,
+int may_setattr(struct mnt_idmap *idmap, struct inode *inode,
 		unsigned int ia_valid);
 int setattr_prepare(struct mnt_idmap *, struct dentry *, struct iattr *);
 extern int inode_newsize_ok(const struct inode *, loff_t offset);
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index ed6cb2ac55fa..894f233083e3 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -154,7 +154,7 @@ LSM_HOOK(int, 0, inode_remove_acl, struct user_namespace *mnt_userns,
 LSM_HOOK(int, 0, inode_need_killpriv, struct dentry *dentry)
 LSM_HOOK(int, 0, inode_killpriv, struct user_namespace *mnt_userns,
 	 struct dentry *dentry)
-LSM_HOOK(int, -EOPNOTSUPP, inode_getsecurity, struct user_namespace *mnt_userns,
+LSM_HOOK(int, -EOPNOTSUPP, inode_getsecurity, struct mnt_idmap *idmap,
 	 struct inode *inode, const char *name, void **buffer, bool alloc)
 LSM_HOOK(int, -EOPNOTSUPP, inode_setsecurity, struct inode *inode,
 	 const char *name, const void *value, size_t size, int flags)
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 00fee52df842..0d4531fd46e7 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -68,11 +68,11 @@ extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int);
 extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
 extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
 extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
-struct dentry *lookup_one(struct user_namespace *, const char *, struct dentry *, int);
-struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns,
+struct dentry *lookup_one(struct mnt_idmap *, const char *, struct dentry *, int);
+struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
 				   const char *name, struct dentry *base,
 				   int len);
-struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
+struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
 					    const char *name,
 					    struct dentry *base, int len);
 
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 0cd89ebd4bb6..d6c119e31d7a 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -396,7 +396,7 @@ extern int nfs_getattr(struct mnt_idmap *, const struct path *,
 		       struct kstat *, u32, unsigned int);
 extern void nfs_access_add_cache(struct inode *, struct nfs_access_entry *, const struct cred *);
 extern void nfs_access_set_mask(struct nfs_access_entry *, u32);
-extern int nfs_permission(struct user_namespace *, struct inode *, int);
+extern int nfs_permission(struct mnt_idmap *, struct inode *, int);
 extern int nfs_open(struct inode *, struct file *);
 extern int nfs_attribute_cache_expired(struct inode *inode);
 extern int nfs_revalidate_inode(struct inode *inode, unsigned long flags);
diff --git a/include/linux/security.h b/include/linux/security.h
index 1ba1f4e70b50..d9cd7b2d16a2 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -158,7 +158,7 @@ int cap_inode_removexattr(struct user_namespace *mnt_userns,
 int cap_inode_need_killpriv(struct dentry *dentry);
 int cap_inode_killpriv(struct user_namespace *mnt_userns,
 		       struct dentry *dentry);
-int cap_inode_getsecurity(struct user_namespace *mnt_userns,
+int cap_inode_getsecurity(struct mnt_idmap *idmap,
 			  struct inode *inode, const char *name, void **buffer,
 			  bool alloc);
 extern int cap_mmap_addr(unsigned long addr);
@@ -378,7 +378,7 @@ int security_inode_removexattr(struct user_namespace *mnt_userns,
 int security_inode_need_killpriv(struct dentry *dentry);
 int security_inode_killpriv(struct user_namespace *mnt_userns,
 			    struct dentry *dentry);
-int security_inode_getsecurity(struct user_namespace *mnt_userns,
+int security_inode_getsecurity(struct mnt_idmap *idmap,
 			       struct inode *inode, const char *name,
 			       void **buffer, bool alloc);
 int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags);
@@ -936,12 +936,12 @@ static inline int security_inode_killpriv(struct user_namespace *mnt_userns,
 	return cap_inode_killpriv(mnt_userns, dentry);
 }
 
-static inline int security_inode_getsecurity(struct user_namespace *mnt_userns,
+static inline int security_inode_getsecurity(struct mnt_idmap *idmap,
 					     struct inode *inode,
 					     const char *name, void **buffer,
 					     bool alloc)
 {
-	return cap_inode_getsecurity(mnt_userns, inode, name, buffer, alloc);
+	return cap_inode_getsecurity(idmap, inode, name, buffer, alloc);
 }
 
 static inline int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags)
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index 2e7dd44926e4..b39d156e0098 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -56,25 +56,25 @@ struct xattr {
 };
 
 ssize_t __vfs_getxattr(struct dentry *, struct inode *, const char *, void *, size_t);
-ssize_t vfs_getxattr(struct user_namespace *, struct dentry *, const char *,
+ssize_t vfs_getxattr(struct mnt_idmap *, struct dentry *, const char *,
 		     void *, size_t);
 ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
 int __vfs_setxattr(struct user_namespace *, struct dentry *, struct inode *,
 		   const char *, const void *, size_t, int);
 int __vfs_setxattr_noperm(struct user_namespace *, struct dentry *,
 			  const char *, const void *, size_t, int);
-int __vfs_setxattr_locked(struct user_namespace *, struct dentry *,
+int __vfs_setxattr_locked(struct mnt_idmap *, struct dentry *,
 			  const char *, const void *, size_t, int,
 			  struct inode **);
-int vfs_setxattr(struct user_namespace *, struct dentry *, const char *,
+int vfs_setxattr(struct mnt_idmap *, struct dentry *, const char *,
 		 const void *, size_t, int);
 int __vfs_removexattr(struct user_namespace *, struct dentry *, const char *);
-int __vfs_removexattr_locked(struct user_namespace *, struct dentry *,
+int __vfs_removexattr_locked(struct mnt_idmap *, struct dentry *,
 			     const char *, struct inode **);
-int vfs_removexattr(struct user_namespace *, struct dentry *, const char *);
+int vfs_removexattr(struct mnt_idmap *, struct dentry *, const char *);
 
 ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size);
-int vfs_getxattr_alloc(struct user_namespace *mnt_userns,
+int vfs_getxattr_alloc(struct mnt_idmap *idmap,
 		       struct dentry *dentry, const char *name,
 		       char **xattr_value, size_t size, gfp_t flags);