From patchwork Sat May 15 00:27:33 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 440066 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_BLOCKED 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 A44F0C43461 for ; Sat, 15 May 2021 00:27:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89E076145A for ; Sat, 15 May 2021 00:27:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234524AbhEOA2q (ORCPT ); Fri, 14 May 2021 20:28:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:44072 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230022AbhEOA2q (ORCPT ); Fri, 14 May 2021 20:28:46 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0705B61440; Sat, 15 May 2021 00:27:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1621038454; bh=5TKQccw0MfrPcBro+UF6pP1bAi79nl8XEtlMz/Eb7KU=; h=Date:From:To:Subject:In-Reply-To:From; b=Wwg+CCI4p7eGLnxLqkFKQUdnEXuHkZwRP2dl1wKHREtypRr95DIexmQbg7hPrjZUV SpYdNMFhJ99nsJdfYVoa78q8dTFFZGAchrbLNCwAwZMlVLg+4lm6yV43OKQqtiQNhd Xz0zdjaa2dcAfo7/BwyRlgw9YtOEy9SyP71wqHjQ= Date: Fri, 14 May 2021 17:27:33 -0700 From: Andrew Morton To: akpm@linux-foundation.org, anatoly.trosinenko@gmail.com, anton@tuxera.com, jouni.roivas@tuxera.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, slava@dubeyko.com, stable@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 11/13] hfsplus: prevent corruption in shrinking truncate Message-ID: <20210515002733.KxUyvD09_%akpm@linux-foundation.org> In-Reply-To: <20210514172634.9018621171d5334ceee97e95@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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);