From patchwork Thu Feb 2 20:44:22 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 13126717 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 D70FFC64ED9 for ; Thu, 2 Feb 2023 20:44:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232978AbjBBUok (ORCPT ); Thu, 2 Feb 2023 15:44:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41650 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232680AbjBBUog (ORCPT ); Thu, 2 Feb 2023 15:44:36 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C70A47D9E; Thu, 2 Feb 2023 12:44:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:MIME-Version: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:In-Reply-To:References; bh=N5DDGPQCQApO6zBKJzZWPvZ6faGorf6EH2GURRa+zbA=; b=f4UYhP5SSJPpuEBQlMz7006pDd WeQsd33O7QvKUktKYkseuuQqIsrRzMbMano2OEp7/OVp1r4Ju5WDAzuV18VtLzT1zpKgn8X3LiS+X 0KZ440PySw2UE0+App6GnHcRpyR1dv6db6hSXFy10sM/IrIvqjprUdz1/eMCYBlcPNdK62mwSV4Qo fWcmX/9pX+GGhMX3t9j4AI+3LzBfgZQywwgfU8HlnpzVU2kTuewBcClrYN230HBQ8fY8ayQUEM4e7 hUvYLBXkHgKja0q7ZQVy1jDr9XdCj/gydOTLtWUeEBJt41cTkeTBvK7mPXfYvHbapXcjikAganER/ KyJPX82A==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pNgRa-00Di7J-HD; Thu, 02 Feb 2023 20:44:30 +0000 From: "Matthew Wilcox (Oracle)" To: linux-fsdevel@vger.kernel.org Cc: "Matthew Wilcox (Oracle)" , linux-afs@lists.infradead.org, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org, Hugh Dickins , linux-kernel@vger.kernel.org, fstests@vger.kernel.org Subject: [PATCH 0/5] Fix a minor POSIX conformance problem Date: Thu, 2 Feb 2023 20:44:22 +0000 Message-Id: <20230202204428.3267832-1-willy@infradead.org> X-Mailer: git-send-email 2.37.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org POSIX requires that on ftruncate() expansion, the new bytes must read as zeroes. If someone's mmap()ed the file and stored past EOF, for most filesystems the bytes in that page will be not-zero. It's a pretty minor violation; someone could race you and write to the file between the ftruncate() call and you reading from it, but it's a bit of a QOI violation. I've tested xfs (passes before & after), ext4 and tmpfs (both fail before, pass after). Testing from other FS developers appreciated. fstest to follow; not sure how to persuade git-send-email to work on multiple repositories Matthew Wilcox (Oracle) (5): truncate: Zero bytes after 'oldsize' if we're expanding the file ext4: Zero bytes after 'oldsize' if we're expanding the file tmpfs: Zero bytes after 'oldsize' if we're expanding the file afs: Zero bytes after 'oldsize' if we're expanding the file btrfs: Zero bytes after 'oldsize' if we're expanding the file fs/afs/inode.c | 2 ++ fs/btrfs/inode.c | 1 + fs/ext4/inode.c | 1 + mm/shmem.c | 2 ++ mm/truncate.c | 7 +++++-- 5 files changed, 11 insertions(+), 2 deletions(-)