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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DAC5DC4167B for ; Mon, 4 Dec 2023 17:02:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229708AbjLDRCl (ORCPT ); Mon, 4 Dec 2023 12:02:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53718 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229453AbjLDRCj (ORCPT ); Mon, 4 Dec 2023 12:02:39 -0500 Received: from mx07-00178001.pphosted.com (mx07-00178001.pphosted.com [185.132.182.106]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 549D6B9 for ; Mon, 4 Dec 2023 09:02:45 -0800 (PST) Received: from pps.filterd (m0369458.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.17.1.22/8.17.1.22) with ESMTP id 3B4Bnm3I027658; Mon, 4 Dec 2023 18:02:32 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=foss.st.com; h= message-id:date:mime-version:subject:to:cc:references:from :in-reply-to:content-type:content-transfer-encoding; s= selector1; bh=WQKPT/9MbLKDIXnkNmjJg5GFttYLgVQHEvKahTCagBk=; b=GK 8LMuOv9RBwxlUOk6/A37nnVxuf4lJRlrChmJnIKDgmGfV2SvlADt180wZ45i3shb SEtM+gT9SOPvcNl09SbgUo79fO1/8WbzXoDYZ8vhdAxpKAkQkpqmZktOL1tC/zeP YxVzivJuQB7R5b5SIee2oAQRH0aqYlSp7mnFxCnzmgtsUgmWdcrGSsTdHzoRHmeT G5eJjxGsfEvQEen1BVLev2w3MKBY+xH1skJXFnw2ta195jOKheuI/mc5bfnm7Exd K8Z5RGclO2jIqWK7YU83l0M9N8MgVxVlBJWV5sre4hh3VlmI6gsDBNisYpsm6iCt d5IEf6OKsm8ughJPFYZg== Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com (PPS) with ESMTPS id 3urf14xfw4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 04 Dec 2023 18:02:32 +0100 (CET) Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id A8DBA10008B; Mon, 4 Dec 2023 18:02:29 +0100 (CET) Received: from Webmail-eu.st.com (shfdag1node2.st.com [10.75.129.70]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id B3A2026029D; Mon, 4 Dec 2023 18:02:29 +0100 (CET) Received: from [10.201.20.163] (10.201.20.163) by SHFDAG1NODE2.st.com (10.75.129.70) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Mon, 4 Dec 2023 18:02:29 +0100 Message-ID: Date: Mon, 4 Dec 2023 18:02:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] tee: Use iov_iter to better support shared buffer registration Content-Language: en-US To: Jens Axboe , Sumit Garg , Al Viro CC: Jens Wiklander , Christoph Hellwig , , References: <20231129164439.1130903-1-arnaud.pouliquen@foss.st.com> <60b67bd5-36c3-4318-9a2b-bcf172681d45@foss.st.com> <40902a86-3b88-45bc-bb6f-2de0eb48dc9d@foss.st.com> <438a8b44-ea5f-4e13-bd7e-e1c2e2a481c4@kernel.dk> From: Arnaud POULIQUEN Organization: STMicroelectronics In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.201.20.163] X-ClientProxiedBy: EQNCAS1NODE3.st.com (10.75.129.80) To SHFDAG1NODE2.st.com (10.75.129.70) X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.997,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-12-04_16,2023-12-04_01,2023-05-22_02 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 12/4/23 17:40, Jens Axboe wrote: > On 12/4/23 9:36 AM, Jens Axboe wrote: >> On 12/4/23 5:42 AM, Sumit Garg wrote: >>> IMO, access_ok() should be the first thing that import_ubuf() or >>> import_single_range() should do, something as follows: >>> >>> diff --git a/lib/iov_iter.c b/lib/iov_iter.c >>> index 8ff6824a1005..4aee0371824c 100644 >>> --- a/lib/iov_iter.c >>> +++ b/lib/iov_iter.c >>> @@ -1384,10 +1384,10 @@ EXPORT_SYMBOL(import_single_range); >>> >>> int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i) >>> { >>> - if (len > MAX_RW_COUNT) >>> - len = MAX_RW_COUNT; >>> if (unlikely(!access_ok(buf, len))) >>> return -EFAULT; >>> + if (len > MAX_RW_COUNT) >>> + len = MAX_RW_COUNT; >>> >>> iov_iter_ubuf(i, rw, buf, len); >>> return 0; >>> >>> Jens A., Al Viro, >>> >>> Was there any particular reason which I am unaware of to perform >>> access_ok() check on modified input length? >> >> This change makes sense to me, and seems consistent with what is done >> elsewhere too. > > For some reason I missed import_single_range(), which does it the same > way as import_ubuf() currently does - cap the range before the > access_ok() check. The vec variants sum as they go, but access_ok() > before the range. > > I think part of the issue here is that the single range imports return 0 > for success and -ERROR otherwise. This means that the caller does not > know if the full range was imported or not. OTOH, we always cap any data > transfer at MAX_RW_COUNT, so may make more sense to fix up the caller > here. > Should we limit to MAX_RW_COUNT or return an error? Seems to me that limiting could generate side effect later that could be not simple to debug. >>> int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i) >>> { >>> - if (len > MAX_RW_COUNT) >>> + return -EFAULT; >>> if (unlikely(!access_ok(buf, len))) >>> return -EFAULT; >>> >>> iov_iter_ubuf(i, rw, buf, len); >>> return 0; or perhaps just remove the test as __access_ok() already tests that the size < TASK_SIZE https://elixir.bootlin.com/linux/v6.7-rc4/source/include/asm-generic/access_ok.h#L31 Thanks, Arnaud