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 5F7C5C43219 for ; Wed, 9 Nov 2022 14:36:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231621AbiKIOgk (ORCPT ); Wed, 9 Nov 2022 09:36:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231213AbiKIOgi (ORCPT ); Wed, 9 Nov 2022 09:36:38 -0500 Received: from fudo.makrotopia.org (fudo.makrotopia.org [IPv6:2a07:2ec0:3002::71]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC0C310A1; Wed, 9 Nov 2022 06:36:37 -0800 (PST) Received: from local by fudo.makrotopia.org with esmtpsa (TLS1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.94.2) (envelope-from ) id 1osmBa-0008KM-BE; Wed, 09 Nov 2022 15:36:14 +0100 Date: Wed, 9 Nov 2022 14:36:11 +0000 From: Daniel Golle To: Matthew Wilcox Cc: Jens Axboe , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Davidlohr Bueso , "Martin K. Petersen" , Chaitanya Kulkarni , Ming Lei , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-efi@vger.kernel.org Subject: Re: [PATCH v4 2/5] block: add partition parser for U-Boot uImage.FIT Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 09, 2022 at 01:58:29PM +0000, Matthew Wilcox wrote: > On Tue, Nov 08, 2022 at 11:03:16PM +0000, Daniel Golle wrote: > > + /* map first page */ > > + page = read_mapping_page( > > + mapping, fit_start_sector >> (PAGE_SHIFT - SECTOR_SHIFT), NULL); > > + > > + if (IS_ERR(page)) > > + return -EFAULT; > > + > > + if (PageError(page)) > > + return -EFAULT; > > Why are you checking for PageError? You won't ever get a page with an > error back from read_mapping_page(). And you have the real error in > 'page', so why return -EFAUlT, which would indicate a problem copying > from the user. Also, this is a great place to use the new folio APIs > instead of the old page APIs. So: > > folio = read_mapping_folio(mapping, > fit_start_sector >> PAGE_SECTORS_SHIFT, NULL); > if (IS_ERR(folio)) > return PTR_ERR(folio); > > > + init_fit = page_address(page); > > init_fit = folio_address(folio) + > offset_in_folio(folio, fit_start_sector * SECTOR_SIZE); > > > + if (!init_fit) { > > + put_page(page); > > + return -EFAULT; > > + } > > page_address() or folio_address() can't ever return NULL, you should > just drop this nonsense check. Thank you for the pointers, I will implement your suggestions and post v5 after the upcoming weekend. > > ... actually, why can't you call read_part_sector() and avoid all of > this? I've tried that before and the problem is that read_part_sector() returns a pointer to one sector (typically 512 bytes) of data. And this pointer should not be accesses beyond sector boundaries, right? You'd have to call read_part_sector() again for the next sector. The FIT structure, however, usually exceeds the size of one sector, and having a continous memory area covering the structure as a whole is crucial for libfdt to do its job. I could, of course, use read_part_sector() to copy all sectors covering the FIT structure into a buffer, but that seemed strange given that read_part_sector() actually used read_mapping_page() (and now uses read_mapping_folio()) internally and then returns a pointer to the offset within the page/folio. So why not read it in one piece in first place instead of having it first split up to sectors by read_part_sector() just to then having to reassemble it into a continous buffer again.