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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 6D8CBC47257 for ; Sun, 10 May 2020 00:51:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 506B221775 for ; Sun, 10 May 2020 00:51:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728279AbgEJAvL (ORCPT ); Sat, 9 May 2020 20:51:11 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:65189 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725927AbgEJAvL (ORCPT ); Sat, 9 May 2020 20:51:11 -0400 Received: from fsav302.sakura.ne.jp (fsav302.sakura.ne.jp [153.120.85.133]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 04A0p77S032175; Sun, 10 May 2020 09:51:07 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav302.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav302.sakura.ne.jp); Sun, 10 May 2020 09:51:07 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav302.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 04A0p1V9031999 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sun, 10 May 2020 09:51:06 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH 05/20] tomoyo_write_control(): get rid of pointless access_ok() To: Al Viro , linux-kernel@vger.kernel.org Cc: Linus Torvalds , linux-fsdevel@vger.kernel.org References: <20200509234124.GM23230@ZenIV.linux.org.uk> <20200509234557.1124086-1-viro@ZenIV.linux.org.uk> <20200509234557.1124086-5-viro@ZenIV.linux.org.uk> From: Tetsuo Handa Message-ID: Date: Sun, 10 May 2020 09:50:58 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200509234557.1124086-5-viro@ZenIV.linux.org.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Al. I think that this access_ok() check helps reducing partial writes (either "whole amount was processed" or "not processed at all" unless -ENOMEM). Do you think that such attempt is pointless? Then, please go ahead... On 2020/05/10 8:45, Al Viro wrote: > From: Al Viro > > address is passed only to get_user() > > Signed-off-by: Al Viro > --- > security/tomoyo/common.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c > index 1b467381986f..f93f8acd05f7 100644 > --- a/security/tomoyo/common.c > +++ b/security/tomoyo/common.c > @@ -2662,8 +2662,6 @@ ssize_t tomoyo_write_control(struct tomoyo_io_buffer *head, > > if (!head->write) > return -EINVAL; > - if (!access_ok(buffer, buffer_len)) > - return -EFAULT; > if (mutex_lock_interruptible(&head->io_sem)) > return -EINTR; > head->read_user_buf_avail = 0; >