From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EE8DC3F2C6 for ; Tue, 3 Mar 2020 13:19:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F94A20842 for ; Tue, 3 Mar 2020 13:19:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583241566; bh=cMwa4DWNXNo1OQ3rkVmUi6YKbd5FMSezFjnnsCfdAM0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=uewDSqa3PNMKwV5mafJRAZLhBPN+tyQ1yRhVSOVwOUQoJRdVu9lh68lt+W2UtzNrR Tn0kIMHxdEgHPwbs4Av8j25yQvikEjD2XEPUuIF4bLMNK0JQJl/y/WntwQPEFYbXMW vvZZOiixrWTOC73MGpGRqjI4k3mlNEFL1opOU2z4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729288AbgCCNTZ (ORCPT ); Tue, 3 Mar 2020 08:19:25 -0500 Received: from mail-qk1-f193.google.com ([209.85.222.193]:38549 "EHLO mail-qk1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728330AbgCCNTY (ORCPT ); Tue, 3 Mar 2020 08:19:24 -0500 Received: by mail-qk1-f193.google.com with SMTP id h22so3295914qke.5; Tue, 03 Mar 2020 05:19:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Dq0BrbehtK7dXyNHKSd+EsOqpyv9pUXKpu+rlI2sPy0=; b=dS7oPsIcp/43xUk811EfREN9F0E/R1GAaoEagaxvwV3+zlqbGtVcU7P352DpRveBUL o4ug8Ghz4tfQvW05T4Gyz6fehTJGT2/qKzvpsMjMfvX02AcUmTQ20N14TNAQGZFw93nD sy98slN9mRSb1T/Ef2+8W+i8p15qvv5oODLKp2ia0CyqILrUX8bVSq8qNWdsStPTI8iD ixRbGieZO9m/P702VfNAqnayQ30qKfCxC9CjmDMmWjKAI5I/b0OvBlNvtrTCjxS2KEM/ N+UQy03P/OkJ4BDnTmfPQLM0ECxCdhNsARPcejnqcqXFtL+788rMYq13pgmYk5mkgZRK 7M4A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=Dq0BrbehtK7dXyNHKSd+EsOqpyv9pUXKpu+rlI2sPy0=; b=VFoljd7clZcYp5iDXsrXWJxF6LMAPb5bdq9x0HvdIZftGlqYMP3GYLs35qmalpAc0E E+zAuC1Oxs1aKFRF6MI+vYFEWF8ZewekZbNl2W2EWDNr1rFPb+ekfXdjVdtaZ7nYrjh7 fsR9NkqWH1VHm0Uib2Wz2IoH7w0NBDdd3fZAYrVZnWZ9NVJVr7XXVN89BI46LToBmdo8 cim1mJHwtrG8Xv15LJHO82ReD4Ily0rqEp9QKAj+0zqu92dqBvtd/7A6mc3MzIK9Dc+t yaSNHRsuXsKZyICcv+mqolLlWL6IzmbYKWzySSXUcsekb3h8WQi9pPnK+2Xe0I2My5zE SbJQ== X-Gm-Message-State: ANhLgQ314g46v2o+ivvj+tTdBqzG0W84wAwG7MdRwle8tl05U5AkGPeN 9wiotsUlsGZtjcI6uSk44wvI3+viif8= X-Google-Smtp-Source: ADFU+vvF5+WTDJs1wG460WrGfpTxI7+RdZTc6LshJRnRDEWuGkFnJDLgH0/WGXKpwe1wsVKCyM/XlA== X-Received: by 2002:a37:aa88:: with SMTP id t130mr4252977qke.452.1583241562821; Tue, 03 Mar 2020 05:19:22 -0800 (PST) Received: from localhost ([2620:10d:c091:500::7f70]) by smtp.gmail.com with ESMTPSA id j17sm12534162qth.27.2020.03.03.05.19.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Mar 2020 05:19:22 -0800 (PST) Date: Tue, 3 Mar 2020 08:19:21 -0500 From: Tejun Heo To: Daniel Xu Cc: cgroups@vger.kernel.org, lizefan@huawei.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, kernel-team@fb.com Subject: Re: [PATCH 1/2] kernfs: Add option to enable user xattrs Message-ID: <20200303131921.GB5186@mtj.thefacebook.com> References: <20200303013901.32150-1-dxu@dxuuu.xyz> <20200303013901.32150-2-dxu@dxuuu.xyz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200303013901.32150-2-dxu@dxuuu.xyz> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Mon, Mar 02, 2020 at 05:39:00PM -0800, Daniel Xu wrote: > +static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler, > + struct dentry *unused, struct inode *inode, > + const char *suffix, const void *value, > + size_t size, int flags) > +{ ... > + if (value && atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) { > + ret = -ENOSPC; > + goto dec_out; > + } So, we limit the number of user xattrs here but > + ret = kernfs_vfs_xattr_set(handler, unused, inode, suffix, value, > + size, flags); This will call into simple_xattr_set() which doesn't put any further restriction on size and just calls GFP_KERNEL kmalloc on it allowing users incur high-order allocations. Maybe it'd make sense to limit both the number and size? Thanks. -- tejun