vfs: Check for the IOP_XATTR flag in listxattr

When an inode doesn't support xattrs, turn listxattr off as well.

(When xattrs are "turned off", the VFS still passes security xattr
operations through to security modules, which can still expose inode
security labels that way.)
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/xattr.c

@@ -326,18 +326,19 @@ vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 EXPORT_SYMBOL_GPL(vfs_getxattr);
 
 ssize_t
-vfs_listxattr(struct dentry *d, char *list, size_t size)
+vfs_listxattr(struct dentry *dentry, char *list, size_t size)
 {
+	struct inode *inode = d_inode(dentry);
 	ssize_t error;
 
-	error = security_inode_listxattr(d);
+	error = security_inode_listxattr(dentry);
 	if (error)
 		return error;
+	if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
 		error = -EOPNOTSUPP;
-	if (d->d_inode->i_op->listxattr) {
-		error = d->d_inode->i_op->listxattr(d, list, size);
+		error = inode->i_op->listxattr(dentry, list, size);
 	} else {
-		error = security_inode_listsecurity(d->d_inode, list, size);
+		error = security_inode_listsecurity(inode, list, size);
 		if (size && error > size)
 			error = -ERANGE;
 	}