Merge tag 'ovl-fixes-5.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs fix from Miklos Szeredi:
 "Add a temporary fix for posix acls on idmapped mounts introduced in
  this cycle. A proper fix will be added in the next cycle"

* tag 'ovl-fixes-5.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: turn off SB_POSIXACL with idmapped layers temporarily

Documentation/filesystems/overlayfs.rst

@@ -466,6 +466,10 @@ overlay filesystem and the value of st_ino for filesystem objects may not be
 persistent and could change even while the overlay filesystem is mounted, as
 summarized in the `Inode properties`_ table above.
 
+4) "idmapped mounts"
+When the upper or lower layers are idmapped mounts overlayfs will be mounted
+without support for POSIX Access Control Lists (ACLs). This limitation will
+eventually be lifted.
 
 Changes to underlying filesystems
 ---------------------------------

fs/overlayfs/super.c

@@ -1003,6 +1003,9 @@ ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 			struct dentry *dentry, struct inode *inode,
 			const char *name, void *buffer, size_t size)
 {
+	if (!IS_POSIXACL(inode))
+		return -EOPNOTSUPP;
+
 	return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
 }
 
@@ -1018,6 +1021,9 @@ ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 	struct posix_acl *acl = NULL;
 	int err;
 
+	if (!IS_POSIXACL(inode))
+		return -EOPNOTSUPP;
+
 	/* Check that everything is OK before copy-up */
 	if (value) {
 		acl = posix_acl_from_xattr(&init_user_ns, value, size);
@@ -1960,6 +1966,20 @@ static struct dentry *ovl_get_root(struct super_block *sb,
 	return root;
 }
 
+static bool ovl_has_idmapped_layers(struct ovl_fs *ofs)
+{
+
+	unsigned int i;
+	const struct vfsmount *mnt;
+
+	for (i = 0; i < ofs->numlayer; i++) {
+		mnt = ofs->layers[i].mnt;
+		if (mnt && is_idmapped_mnt(mnt))
+			return true;
+	}
+	return false;
+}
+
 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct path upperpath = { };
@@ -2129,7 +2149,10 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_xattr = ofs->config.userxattr ? ovl_user_xattr_handlers :
 		ovl_trusted_xattr_handlers;
 	sb->s_fs_info = ofs;
-	sb->s_flags |= SB_POSIXACL;
+	if (ovl_has_idmapped_layers(ofs))
+		pr_warn("POSIX ACLs are not yet supported with idmapped layers, mounting without ACL support.\n");
+	else
+		sb->s_flags |= SB_POSIXACL;
 	sb->s_iflags |= SB_I_SKIP_SYNC;
 
 	err = -ENOMEM;