From nobody Fri Sep 5 20:24:39 2025 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 D0EBCC32772 for ; Tue, 23 Aug 2022 11:44:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358278AbiHWLo4 (ORCPT ); Tue, 23 Aug 2022 07:44:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358277AbiHWLlY (ORCPT ); Tue, 23 Aug 2022 07:41:24 -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 65E58CACAA; Tue, 23 Aug 2022 02:29:07 -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 B38F5B81C85; Tue, 23 Aug 2022 09:29:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E332EC433C1; Tue, 23 Aug 2022 09:29:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661246944; bh=Nglrtbc6ZxP9VMKhf1z/sBxfdb47WdpNo/Z79mDaEjg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sOxfmqgPiv/UWueld349rL986V4Sis4cTYwiEctvsJv9tnM2qXPZQyMT++xuLBu/+ m7OzDi6oMPhcaSHwB5c04QnkY+rRzF1AZsBMj08tE/g5ByrQvUvNBJNK0lxgwcWk6C jbNSCYPFz25ymXUM88OqQRkG5frjYrHttx86j7O4= 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 5.4 261/389] ext4: fix extent status tree race in writeback error recovery path Date: Tue, 23 Aug 2022 10:25:39 +0200 Message-Id: <20220823080126.486005521@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080115.331990024@linuxfoundation.org> References: <20220823080115.331990024@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 @@ -1717,7 +1717,14 @@ 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);