From patchwork Tue May 18 18:25:30 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 441774 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED autolearn=unavailable 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 D3503C43460 for ; Tue, 18 May 2021 18:25:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B74FF61353 for ; Tue, 18 May 2021 18:25:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351524AbhERS0t (ORCPT ); Tue, 18 May 2021 14:26:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:58168 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345616AbhERS0t (ORCPT ); Tue, 18 May 2021 14:26:49 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9D18C60FF2; Tue, 18 May 2021 18:25:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1621362330; bh=CqPSGLhnMXmSlNiOlwVKR935f8LNnI2XCJhHXGDtZ9w=; h=Date:From:To:Subject:From; b=vK3h+Ve9GJerhxBLj4cwuYQ7HS2dD2IUmnZ4kKW39ZWikaupkPHaBCGYYgldp/Fmx qzi09cVKoJtQWuIXG1AOgIXFj6h8gzFHhS4tIUDmF/fmbfkHLe2D2l1FUUvci+uKpq 4HkM/6CDzsiq6vmwUapKJJXe3A0nlb65DiJB9Y84= Date: Tue, 18 May 2021 11:25:30 -0700 From: akpm@linux-foundation.org To: anatoly.trosinenko@gmail.com, anton@tuxera.com, jouni.roivas@tuxera.com, mm-commits@vger.kernel.org, slava@dubeyko.com, stable@vger.kernel.org Subject: [merged] hfsplus-prevent-corruption-in-shrinking-truncate.patch removed from -mm tree Message-ID: <20210518182530.Wtn-Dl9pg%akpm@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: hfsplus: prevent corruption in shrinking truncate has been removed from the -mm tree. Its filename was hfsplus-prevent-corruption-in-shrinking-truncate.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Jouni Roivas Subject: hfsplus: prevent corruption in shrinking truncate I believe there are some issues introduced by commit 31651c607151 ("hfsplus: avoid deadlock on file truncation") HFS+ has extent records which always contains 8 extents. In case the first extent record in catalog file gets full, new ones are allocated from extents overflow file. In case shrinking truncate happens to middle of an extent record which locates in extents overflow file, the logic in hfsplus_file_truncate() was changed so that call to hfs_brec_remove() is not guarded any more. Right action would be just freeing the extents that exceed the new size inside extent record by calling hfsplus_free_extents(), and then check if the whole extent record should be removed. However since the guard (blk_cnt > start) is now after the call to hfs_brec_remove(), this has unfortunate effect that the last matching extent record is removed unconditionally. To reproduce this issue, create a file which has at least 10 extents, and then perform shrinking truncate into middle of the last extent record, so that the number of remaining extents is not under or divisible by 8. This causes the last extent record (8 extents) to be removed totally instead of truncating into middle of it. Thus this causes corruption, and lost data. Fix for this is simply checking if the new truncated end is below the start of this extent record, making it safe to remove the full extent record. However call to hfs_brec_remove() can't be moved to it's previous place since we're dropping ->tree_lock and it can cause a race condition and the cached info being invalidated possibly corrupting the node data. Another issue is related to this one. When entering into the block (blk_cnt > start) we are not holding the ->tree_lock. We break out from the loop not holding the lock, but hfs_find_exit() does unlock it. Not sure if it's possible for someone else to take the lock under our feet, but it can cause hard to debug errors and premature unlocking. Even if there's no real risk of it, the locking should still always be kept in balance. Thus taking the lock now just before the check. Link: https://lkml.kernel.org/r/20210429165139.3082828-1-jouni.roivas@tuxera.com Fixes: 31651c607151f ("hfsplus: avoid deadlock on file truncation") Signed-off-by: Jouni Roivas Reviewed-by: Anton Altaparmakov Cc: Anatoly Trosinenko Cc: Viacheslav Dubeyko Cc: Signed-off-by: Andrew Morton --- fs/hfsplus/extents.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/fs/hfsplus/extents.c~hfsplus-prevent-corruption-in-shrinking-truncate +++ a/fs/hfsplus/extents.c @@ -598,13 +598,15 @@ void hfsplus_file_truncate(struct inode res = __hfsplus_ext_cache_extent(&fd, inode, alloc_cnt); if (res) break; - hfs_brec_remove(&fd); - mutex_unlock(&fd.tree->tree_lock); start = hip->cached_start; + if (blk_cnt <= start) + hfs_brec_remove(&fd); + mutex_unlock(&fd.tree->tree_lock); hfsplus_free_extents(sb, hip->cached_extents, alloc_cnt - start, alloc_cnt - blk_cnt); hfsplus_dump_extent(hip->cached_extents); + mutex_lock(&fd.tree->tree_lock); if (blk_cnt > start) { hip->extent_state |= HFSPLUS_EXT_DIRTY; break; @@ -612,7 +614,6 @@ void hfsplus_file_truncate(struct inode alloc_cnt = start; hip->cached_start = hip->cached_blocks = 0; hip->extent_state &= ~(HFSPLUS_EXT_DIRTY | HFSPLUS_EXT_NEW); - mutex_lock(&fd.tree->tree_lock); } hfs_find_exit(&fd);