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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 6F53CC43218 for ; Sun, 28 Apr 2019 13:47:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2DAF320881 for ; Sun, 28 Apr 2019 13:47:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556459245; bh=wHRWVkog4zflnnw0t5JuuQTtmUoa5msQ3jIsMaiS1v0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=BO9cH0fyzD+AmneHtFwXsmRr3MsDQ2Od7S0vouKn0t5qoNcTUMklfFHVNP/Pc2Aky GwF6E8a6T51TeHZyQm+LcsV+lS7TdJzv42FKLEQGR2E9tqP58Kb0Ud92oS+Pxu+Dlp o25u7vRkAaMTG87vygnIuNtF0RfH+u4RHtKlx0Q0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726766AbfD1NrY (ORCPT ); Sun, 28 Apr 2019 09:47:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:46100 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726606AbfD1NrX (ORCPT ); Sun, 28 Apr 2019 09:47:23 -0400 Received: from localhost (c-98-234-77-170.hsd1.ca.comcast.net [98.234.77.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0BF032075D; Sun, 28 Apr 2019 13:47:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556459243; bh=wHRWVkog4zflnnw0t5JuuQTtmUoa5msQ3jIsMaiS1v0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kUklfwF0o1dCpfy9Erdz6AYCdn3uTTfEXPVmo1vzuzpW+paq7AFZ7XS3xkTxSOJuK icWkfoXoY0Zq63Gk0JereoHnlsou9llJBOcw8tQPjVxYwyxfjO97apwRXuXYQVEb6q Eo4O/I8Du81RocdN5cXyWD0JjTRYpif+lOeBwEMs= Date: Sun, 28 Apr 2019 06:47:22 -0700 From: Jaegeuk Kim To: Chao Yu Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, chao@kernel.org, drosen@google.com Subject: Re: [PATCH 1/2] f2fs: fix to avoid potential negative .f_bfree Message-ID: <20190428134722.GC37346@jaegeuk-macbookpro.roam.corp.google.com> References: <20190426095754.85784-1-yuchao0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190426095754.85784-1-yuchao0@huawei.com> User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/26, Chao Yu wrote: > When calculating .f_bfree value in f2fs_statfs(), sbi->unusable_block_count > can be increased after the judgment condition, result in overflow of > .f_bfree in later calculation. This patch fixes to use a temporary signed > variable to save the calculation result of .f_bfree. > > if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) > buf->f_bfree = 0; > else > buf->f_bfree -= sbi->unusable_block_count; Do we just need stat_lock for this? > > Signed-off-by: Chao Yu > --- > fs/f2fs/super.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c > index 2376bb01b5c4..fcc9793dbc2c 100644 > --- a/fs/f2fs/super.c > +++ b/fs/f2fs/super.c > @@ -1216,6 +1216,7 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) > u64 id = huge_encode_dev(sb->s_bdev->bd_dev); > block_t total_count, user_block_count, start_count; > u64 avail_node_count; > + long long bfree; > > total_count = le64_to_cpu(sbi->raw_super->block_count); > user_block_count = sbi->user_block_count; > @@ -1226,10 +1227,12 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf) > buf->f_blocks = total_count - start_count; > buf->f_bfree = user_block_count - valid_user_blocks(sbi) - > sbi->current_reserved_blocks; > - if (unlikely(buf->f_bfree <= sbi->unusable_block_count)) > + > + bfree = buf->f_bfree - sbi->unusable_block_count; > + if (unlikely(bfree < 0)) > buf->f_bfree = 0; > else > - buf->f_bfree -= sbi->unusable_block_count; > + buf->f_bfree = bfree; > > if (buf->f_bfree > F2FS_OPTION(sbi).root_reserved_blocks) > buf->f_bavail = buf->f_bfree - > -- > 2.18.0.rc1