fs: port ->getattr() 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>

1 files changed, 12 insertions, 10 deletions

diff --git a/fs/stat.c b/fs/stat.c
index d6cc74ca8486..cb91bc7c9efd 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -27,7 +27,7 @@
 
 /**
  * generic_fillattr - Fill in the basic attributes from the inode struct
- * @mnt_userns:	user namespace of the mount the inode was found from
+ * @idmap:	idmap of the mount the inode was found from
  * @inode:	Inode to use as the source
  * @stat:	Where to fill in the attributes
  *
@@ -35,15 +35,17 @@
  * found on the VFS inode structure.  This is the default if no getattr inode
  * operation is supplied.
  *
- * If the inode has been found through an idmapped mount the user namespace of
- * the vfsmount must be passed through @mnt_userns. This function will then
- * take care to map the inode according to @mnt_userns before filling in the
+ * If the inode has been found through an idmapped mount the idmap of
+ * the vfsmount must be passed through @idmap. This function will then
+ * take care to map the inode according to @idmap before filling in the
  * uid and gid filds. On non-idmapped mounts or if permission checking is to be
- * performed on the raw inode simply passs init_user_ns.
+ * performed on the raw inode simply passs @nop_mnt_idmap.
  */
-void generic_fillattr(struct user_namespace *mnt_userns, struct inode *inode,
+void generic_fillattr(struct mnt_idmap *idmap, struct inode *inode,
 		      struct kstat *stat)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
+
 	vfsuid_t vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
 	vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
 
@@ -97,7 +99,7 @@ EXPORT_SYMBOL(generic_fill_statx_attr);
 int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
 		      u32 request_mask, unsigned int query_flags)
 {
-	struct user_namespace *mnt_userns;
+	struct mnt_idmap *idmap;
 	struct inode *inode = d_backing_inode(path->dentry);
 
 	memset(stat, 0, sizeof(*stat));
@@ -122,12 +124,12 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
 	stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT |
 				  STATX_ATTR_DAX);
 
-	mnt_userns = mnt_user_ns(path->mnt);
+	idmap = mnt_idmap(path->mnt);
 	if (inode->i_op->getattr)
-		return inode->i_op->getattr(mnt_userns, path, stat,
+		return inode->i_op->getattr(idmap, path, stat,
 					    request_mask, query_flags);
 
-	generic_fillattr(mnt_userns, inode, stat);
+	generic_fillattr(idmap, inode, stat);
 	return 0;
 }
 EXPORT_SYMBOL(vfs_getattr_nosec);