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=-8.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT 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 D50EDC43441 for ; Fri, 23 Nov 2018 07:56:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9C27420820 for ; Fri, 23 Nov 2018 07:56:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="mE/FEvCb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9C27420820 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 S2393555AbeKWSkB (ORCPT ); Fri, 23 Nov 2018 13:40:01 -0500 Received: from m12-14.163.com ([220.181.12.14]:55298 "EHLO m12-14.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389970AbeKWSkA (ORCPT ); Fri, 23 Nov 2018 13:40:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:Subject:Date:Message-Id; bh=1IEg/SqIKsm7V38Ue4 q99mswwyE8Gl2nIKmq6K1khs4=; b=mE/FEvCbMZpRZ1/husbNrg8W1ZNjwB7+E4 Gr7axYsXCJ4RJ98ieFkJ0mtEJL3DstSPiGMYMlM3ltLFyyODTfr35s7IPoxz8IrA Jpx8aJwlgLmGjlBsdSEhHjma+VDRRd9db0skm+oiUYKqDEUNDe9MmQRCnY/Bj/jW mANaaRnQQ= Received: from bp.localdomain (unknown [106.120.213.96]) by smtp10 (Coremail) with SMTP id DsCowAC3P8q6svdbHWnbBQ--.544S3; Fri, 23 Nov 2018 15:56:45 +0800 (CST) From: Pan Bian To: Amir Goldstein , Miklos Szeredi Cc: Al Viro , "J. Bruce Fields" , Christoph Hellwig , linux-kernel , Pan Bian Subject: [PATCH V2] exportfs: do not read dentry after free Date: Fri, 23 Nov 2018 15:56:33 +0800 Message-Id: <1542959793-118334-1-git-send-email-bianpan2016@163.com> X-Mailer: git-send-email 2.7.4 X-CM-TRANSID: DsCowAC3P8q6svdbHWnbBQ--.544S3 X-Coremail-Antispam: 1Uf129KBjvdXoW7Xw47tw45XFyktFWDWw45Wrg_yoWDGwbEka y8Wr48W395CFyxKF48ArWaqr4fKan8ArWqyr4rtr45Za45CrW8JFZayw1fXrs8Ww48Wa45 Cr1DtryUCr1rCjkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUvcSsGvfC2KfnxnUUI43ZEXa7IUnTGQDUUUUU== X-Originating-IP: [106.120.213.96] X-CM-SenderInfo: held01tdqsiiqw6rljoofrz/xtbBzx0IclaD0YfD0wAAs7 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The function dentry_connected calls dput(dentry) to drop the previously acquired reference to dentry. In this case, dentry can be released. After that, IS_ROOT(dentry) checks the condition (dentry == dentry->d_parent), which may result in a use-after-free bug. This patch directly compares dentry with its parent obtained before dropping the reference. Fixes: a056cc8934c("exportfs: stop retrying once we race with rename/remove") Signed-off-by: Pan Bian --- V2: get rid of the comment --- fs/exportfs/expfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c index 645158d..a69aaf5 100644 --- a/fs/exportfs/expfs.c +++ b/fs/exportfs/expfs.c @@ -77,7 +77,7 @@ static bool dentry_connected(struct dentry *dentry) struct dentry *parent = dget_parent(dentry); dput(dentry); - if (IS_ROOT(dentry)) { + if (dentry == parent) { dput(parent); return false; } -- 2.7.4