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 X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 8EADAC43462 for ; Mon, 10 May 2021 12:37:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 675736145F for ; Mon, 10 May 2021 12:37:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346804AbhEJMco (ORCPT ); Mon, 10 May 2021 08:32:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:53778 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237305AbhEJLLt (ORCPT ); Mon, 10 May 2021 07:11:49 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CC2356192E; Mon, 10 May 2021 11:08:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620644937; bh=m1/6NUWW1FDP/McTnMl3GIptawWKsdd2yROLn8Oi0kE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IbEF3hCKwrIXHmVUx5uFdVoPBWdLwTgv99uSw1ctpVYikia4M8efP1Rh0cC1/tgtX ZRbi8qvowDXBlbaaJKeQ4BU/IS82C8hK4oWrBZtq8+23JfuD62SVN+BCeGmm+ZKsEF eD3njFDqc/eJeU0tVBo/JV9y+2mOEjmzQlACvT+0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Robbie Ko , Chung-Chiang Cheng , Filipe Manana , BingJing Chang , David Sterba , Sasha Levin Subject: [PATCH 5.12 284/384] btrfs: fix a potential hole punching failure Date: Mon, 10 May 2021 12:21:13 +0200 Message-Id: <20210510102024.181662447@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210510102014.849075526@linuxfoundation.org> References: <20210510102014.849075526@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: BingJing Chang [ Upstream commit 3227788cd369d734d2d3cd94f8af7536b60fa552 ] In commit d77815461f04 ("btrfs: Avoid trucating page or punching hole in a already existed hole."), existing holes can be skipped by calling find_first_non_hole() to adjust start and len. However, if the given len is invalid and large, when an EXTENT_MAP_HOLE extent is found, len will not be set to zero because (em->start + em->len) is less than (start + len). Then the ret will be 1 but len will not be set to 0. The propagated non-zero ret will result in fallocate failure. In the while-loop of btrfs_replace_file_extents(), len is not updated every time before it calls find_first_non_hole(). That is, after btrfs_drop_extents() successfully drops the last non-hole file extent, it may fail with ENOSPC when attempting to drop a file extent item representing a hole. The problem can happen. After it calls find_first_non_hole(), the cur_offset will be adjusted to be larger than or equal to end. However, since the len is not set to zero, the break-loop condition (ret && !len) will not be met. After it leaves the while-loop, fallocate will return 1, which is an unexpected return value. We're not able to construct a reproducible way to let btrfs_drop_extents() fail with ENOSPC after it drops the last non-hole file extent but with remaining holes left. However, it's quite easy to fix. We just need to update and check the len every time before we call find_first_non_hole(). To make the while loop more readable, we also pull the variable updates to the bottom of loop like this: while (cur_offset < end) { ... // update cur_offset & len // advance cur_offset & len in hole-punching case if needed } Reported-by: Robbie Ko Fixes: d77815461f04 ("btrfs: Avoid trucating page or punching hole in a already existed hole.") CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Robbie Ko Reviewed-by: Chung-Chiang Cheng Reviewed-by: Filipe Manana Signed-off-by: BingJing Chang Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/file.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 4130523a77c9..6eb72c9b15a7 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -2729,8 +2729,6 @@ int btrfs_replace_file_extents(struct inode *inode, struct btrfs_path *path, extent_info->file_offset += replace_len; } - cur_offset = drop_args.drop_end; - ret = btrfs_update_inode(trans, root, BTRFS_I(inode)); if (ret) break; @@ -2750,7 +2748,9 @@ int btrfs_replace_file_extents(struct inode *inode, struct btrfs_path *path, BUG_ON(ret); /* shouldn't happen */ trans->block_rsv = rsv; - if (!extent_info) { + cur_offset = drop_args.drop_end; + len = end - cur_offset; + if (!extent_info && len) { ret = find_first_non_hole(BTRFS_I(inode), &cur_offset, &len); if (unlikely(ret < 0)) -- 2.30.2