fs: port ->get_acl() 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, 8 insertions, 7 deletions

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index d7bc81fc0840..17e141a94671 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -111,7 +111,7 @@ void forget_all_cached_acls(struct inode *inode)
 }
 EXPORT_SYMBOL(forget_all_cached_acls);
 
-static struct posix_acl *__get_acl(struct user_namespace *mnt_userns,
+static struct posix_acl *__get_acl(struct mnt_idmap *idmap,
 				   struct dentry *dentry, struct inode *inode,
 				   int type)
 {
@@ -154,7 +154,7 @@ static struct posix_acl *__get_acl(struct user_namespace *mnt_userns,
 	 * we'll just create the negative cache entry.
 	 */
 	if (dentry && inode->i_op->get_acl) {
-		acl = inode->i_op->get_acl(mnt_userns, dentry, type);
+		acl = inode->i_op->get_acl(idmap, dentry, type);
 	} else if (inode->i_op->get_inode_acl) {
 		acl = inode->i_op->get_inode_acl(inode, type, false);
 	} else {
@@ -181,7 +181,7 @@ static struct posix_acl *__get_acl(struct user_namespace *mnt_userns,
 
 struct posix_acl *get_inode_acl(struct inode *inode, int type)
 {
-	return __get_acl(&init_user_ns, NULL, inode, type);
+	return __get_acl(&nop_mnt_idmap, NULL, inode, type);
 }
 EXPORT_SYMBOL(get_inode_acl);
 
@@ -1121,7 +1121,7 @@ EXPORT_SYMBOL_GPL(vfs_set_acl);
 
 /**
  * vfs_get_acl - get posix acls
- * @mnt_userns: user namespace of the mount
+ * @idmap: idmap of the mount
  * @dentry: the dentry based on which to retrieve the posix acls
  * @acl_name: the name of the posix acl
  *
@@ -1130,9 +1130,10 @@ EXPORT_SYMBOL_GPL(vfs_set_acl);
  *
  * Return: On success POSIX ACLs in VFS format, on error negative errno.
  */
-struct posix_acl *vfs_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *vfs_get_acl(struct mnt_idmap *idmap,
 			      struct dentry *dentry, const char *acl_name)
 {
+	struct user_namespace *mnt_userns = mnt_idmap_owner(idmap);
 	struct inode *inode = d_inode(dentry);
 	struct posix_acl *acl;
 	int acl_type, error;
@@ -1154,7 +1155,7 @@ struct posix_acl *vfs_get_acl(struct user_namespace *mnt_userns,
 	if (S_ISLNK(inode->i_mode))
 		return ERR_PTR(-EOPNOTSUPP);
 
-	acl = __get_acl(mnt_userns, dentry, inode, acl_type);
+	acl = __get_acl(idmap, dentry, inode, acl_type);
 	if (IS_ERR(acl))
 		return acl;
 	if (!acl)
@@ -1256,7 +1257,7 @@ ssize_t do_get_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 	ssize_t error;
 	struct posix_acl *acl;
 
-	acl = vfs_get_acl(mnt_idmap_owner(idmap), dentry, acl_name);
+	acl = vfs_get_acl(idmap, dentry, acl_name);
 	if (IS_ERR(acl))
 		return PTR_ERR(acl);