From nobody Sat Feb 7 12:28:18 2026 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 7D835C32774 for ; Tue, 23 Aug 2022 10:07:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352228AbiHWKHG (ORCPT ); Tue, 23 Aug 2022 06:07:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43874 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352401AbiHWKBw (ORCPT ); Tue, 23 Aug 2022 06:01:52 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 75F3182FB9; Tue, 23 Aug 2022 01:49:31 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 0158EB81BF8; Tue, 23 Aug 2022 08:49:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35CD2C433C1; Tue, 23 Aug 2022 08:49:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661244568; bh=CVSo7CjZGkrDLL6BVK+W8HD7/XYyGy3iyIB5aosrHrs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fKrSMzYZWVRAnqLrREASiOHOz5WqPMCaJf0KOL+Kpl065iLSYM69/nNzr9/SP33ls J08uc4TnC8zmmcjW5Rc0wHnYQ831+9YljU6eFGqtykUMpmftYTlV35I9yQWsaqtln7 AQ4AZcZlvI44nsd0bNccMzZhiZddJo97KxkZrUJA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, stable@kernel.org, Ye Bin , Eric Whitney , Theodore Tso Subject: [PATCH 4.14 156/229] ext4: fix extent status tree race in writeback error recovery path Date: Tue, 23 Aug 2022 10:25:17 +0200 Message-Id: <20220823080059.248175868@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080053.202747790@linuxfoundation.org> References: <20220823080053.202747790@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Eric Whitney commit 7f0d8e1d607c1a4fa9a27362a108921d82230874 upstream. A race can occur in the unlikely event ext4 is unable to allocate a physical cluster for a delayed allocation in a bigalloc file system during writeback. Failure to allocate a cluster forces error recovery that includes a call to mpage_release_unused_pages(). That function removes any corresponding delayed allocated blocks from the extent status tree. If a new delayed write is in progress on the same cluster simultaneously, resulting in the addition of an new extent containing one or more blocks in that cluster to the extent status tree, delayed block accounting can be thrown off if that delayed write then encounters a similar cluster allocation failure during future writeback. Write lock the i_data_sem in mpage_release_unused_pages() to fix this problem. Ext4's block/cluster accounting code for bigalloc relies on i_data_sem for mutual exclusion, as is found in the delayed write path, and the locking in mpage_release_unused_pages() is missing. Cc: stable@kernel.org Reported-by: Ye Bin Signed-off-by: Eric Whitney Link: https://lore.kernel.org/r/20220615160530.1928801-1-enwlinux@gmail.com Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/inode.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1754,7 +1754,14 @@ static void mpage_release_unused_pages(s ext4_lblk_t start, last; start =3D index << (PAGE_SHIFT - inode->i_blkbits); last =3D end << (PAGE_SHIFT - inode->i_blkbits); + + /* + * avoid racing with extent status tree scans made by + * ext4_insert_delayed_block() + */ + down_write(&EXT4_I(inode)->i_data_sem); ext4_es_remove_extent(inode, start, last - start + 1); + up_write(&EXT4_I(inode)->i_data_sem); } =20 pagevec_init(&pvec, 0);