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=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, FREEMAIL_REPLYTO_END_DIGIT,HEADER_FROM_DIFFERENT_DOMAINS,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 172CEC43441 for ; Tue, 27 Nov 2018 09:57:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D098220873 for ; Tue, 27 Nov 2018 09:57:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="jyhq4+Bp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D098220873 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=163.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730404AbeK0Uyj (ORCPT ); Tue, 27 Nov 2018 15:54:39 -0500 Received: from m12-14.163.com ([220.181.12.14]:56603 "EHLO m12-14.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726431AbeK0Uyj (ORCPT ); Tue, 27 Nov 2018 15:54:39 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Date:From:Subject:Message-ID:MIME-Version; bh=ZnzyO cQyoiiHH6J4MMHT8p8+w3Fdx9yxY66n4oJl0S8=; b=jyhq4+BpKtkIPG9uMp7fU yI3W2QBIcCc2eQ1wIBFmQ5VnFWbpO61I3CFjsAiPjO5isma5hmsOL1hS/hmBFtau 5eubxJCvJyoMRCmwENBCsOdApissmtiw6YjW4v0A7OtrFYm0UFZiCz+vOZzODMqK GQzlgga2ZdxbNv0T487KT8= Received: from bp (unknown [106.120.213.96]) by smtp10 (Coremail) with SMTP id DsCowABHlMz3FP1blOiUCA--.55858S2; Tue, 27 Nov 2018 17:57:11 +0800 (CST) Date: Tue, 27 Nov 2018 17:57:12 +0800 From: PanBian To: Jan Kara Cc: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] namei: free new_dentry late Message-ID: <20181127095712.GA32100@bp> Reply-To: PanBian References: <1543104923-81192-1-git-send-email-bianpan2016@163.com> <20181127092551.GC16301@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181127092551.GC16301@quack2.suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) X-CM-TRANSID: DsCowABHlMz3FP1blOiUCA--.55858S2 X-Coremail-Antispam: 1Uf129KBjvJXoW7ZFWxWFWDKF43tFWrCF1rZwb_yoW8CrWDpF 4rKay8tF4fWrW0kFn3ZFs5Z3W8Zr4Igw109r109ryxtr9aqry5tFs7Wr4kuFy3urWrur1U XF48KF15Xa13ZaDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jypBfUUUUU= X-Originating-IP: [106.120.213.96] X-CM-SenderInfo: held01tdqsiiqw6rljoofrz/1tbiDhcMclXlpnp-6wAAsf Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 27, 2018 at 10:25:51AM +0100, Jan Kara wrote: > On Sun 25-11-18 08:15:23, Pan Bian wrote: > > After calling dput(new_dentry), new_dentry is passed to fsnotify_move. > > This may result in a use-after-free bug. This patch moves the put > > operation late. > > > > Fixes: da1ce0670c14("vfs: add cross-rename") > > Signed-off-by: Pan Bian > > The code is actually fine AFAICT. One new_dentry reference is passed into > vfs_rename() and another one is acquired directly inside vfs_rename(). That > is the one dropped early but there's still the original reference passed in > protecting new_dentry from freeing. Am I missing something? I am not quite sure about the actual execution logic. But I guess new_dentry reference may be dropped outside vfs_rename in cocurrent executions. Otherwise, there is no need to acquire & drop new_dentry reference as it is always alive along vfs_rename. Best regards, Pan > > Honza > > > --- > > V2: correct the fixes commit information > > --- > > fs/namei.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/namei.c b/fs/namei.c > > index 0cab649..8b104d9 100644 > > --- a/fs/namei.c > > +++ b/fs/namei.c > > @@ -4498,7 +4498,6 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, > > unlock_two_nondirectories(source, target); > > else if (target) > > inode_unlock(target); > > - dput(new_dentry); > > if (!error) { > > fsnotify_move(old_dir, new_dir, old_name.name, is_dir, > > !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); > > @@ -4507,6 +4506,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, > > new_is_dir, NULL, new_dentry); > > } > > } > > + dput(new_dentry); > > release_dentry_name_snapshot(&old_name); > > > > return error; > > -- > > 2.7.4 > > > > > -- > Jan Kara > SUSE Labs, CR