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>

2 files changed, 10 insertions, 8 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index ad33253ed7e9..3ea4fc54f469 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -515,14 +515,16 @@ struct posix_acl *ovl_get_acl_path(const struct path *path,
 {
 	struct posix_acl *real_acl, *clone;
 	struct user_namespace *mnt_userns;
+	struct mnt_idmap *idmap;
 	struct inode *realinode = d_inode(path->dentry);
 
-	mnt_userns = mnt_user_ns(path->mnt);
+	idmap = mnt_idmap(path->mnt);
+	mnt_userns = mnt_idmap_owner(idmap);
 
 	if (noperm)
 		real_acl = get_inode_acl(realinode, posix_acl_type(acl_name));
 	else
-		real_acl = vfs_get_acl(mnt_userns, path->dentry, acl_name);
+		real_acl = vfs_get_acl(idmap, path->dentry, acl_name);
 	if (IS_ERR_OR_NULL(real_acl))
 		return real_acl;
 
@@ -555,7 +557,7 @@ struct posix_acl *ovl_get_acl_path(const struct path *path,
  *
  * This is obviously only relevant when idmapped layers are used.
  */
-struct posix_acl *do_ovl_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *do_ovl_get_acl(struct mnt_idmap *idmap,
 				 struct inode *inode, int type,
 				 bool rcu, bool noperm)
 {
@@ -618,7 +620,7 @@ static int ovl_set_or_remove_acl(struct dentry *dentry, struct inode *inode,
 
 		ovl_path_lower(dentry, &realpath);
 		old_cred = ovl_override_creds(dentry->d_sb);
-		real_acl = vfs_get_acl(mnt_user_ns(realpath.mnt), realdentry,
+		real_acl = vfs_get_acl(mnt_idmap(realpath.mnt), realdentry,
 				       acl_name);
 		revert_creds(old_cred);
 		if (IS_ERR(real_acl)) {
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index b6e17f631b53..1e8b0be85e4b 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -610,18 +610,18 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
 
 #ifdef CONFIG_FS_POSIX_ACL
-struct posix_acl *do_ovl_get_acl(struct user_namespace *mnt_userns,
+struct posix_acl *do_ovl_get_acl(struct mnt_idmap *idmap,
 				 struct inode *inode, int type,
 				 bool rcu, bool noperm);
 static inline struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type,
 						  bool rcu)
 {
-	return do_ovl_get_acl(&init_user_ns, inode, type, rcu, true);
+	return do_ovl_get_acl(&nop_mnt_idmap, inode, type, rcu, true);
 }
-static inline struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
+static inline struct posix_acl *ovl_get_acl(struct mnt_idmap *idmap,
 					    struct dentry *dentry, int type)
 {
-	return do_ovl_get_acl(mnt_userns, d_inode(dentry), type, false, false);
+	return do_ovl_get_acl(idmap, d_inode(dentry), type, false, false);
 }
 int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 		struct posix_acl *acl, int type);