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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 D480DC432C3 for ; Tue, 19 Nov 2019 05:24:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A8DBF222A2 for ; Tue, 19 Nov 2019 05:24:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574141045; bh=IzBxVfj66kSqHj1aY66h/C8EPY94WqVzXPC6EUbI7x4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=YVKhkn25AjyYUhOOe1rT85r+6l6GMDTggUJz7ICszP3BajcoqboNaVDqW7wxOwtv0 hrHjrSnF4EoO9FVVzBzDCNX/VayaDog7hs5qwQ8tEdSJBUlmc9aM8CQS59Yrtt4VSn UT0A0MD0A7Eq44KBuRsgOiCqNCCuE/X7n3jbD29k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728126AbfKSFYE (ORCPT ); Tue, 19 Nov 2019 00:24:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:39862 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728115AbfKSFYA (ORCPT ); Tue, 19 Nov 2019 00:24:00 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 4C8B6208C3; Tue, 19 Nov 2019 05:23:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574141039; bh=IzBxVfj66kSqHj1aY66h/C8EPY94WqVzXPC6EUbI7x4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=McHkEriEDouf8Y5+BpwqJ9TAWHFkSBPNLN0csYT/k/utZTBwydKAqFgJjeWDr0JiG qfe+AUpLVTDmxb2odZrINxABOZTnD7IUP/USEZww0o4kjfM5jSSc8Uzta/BdZFz/Gi 4NMrb6O4AM6K+9PJBeK5Vk/tbk4urI1l7ShilthE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro Subject: [PATCH 4.19 025/422] ecryptfs_lookup_interpose(): lower_dentry->d_inode is not stable Date: Tue, 19 Nov 2019 06:13:42 +0100 Message-Id: <20191119051401.707458888@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191119051400.261610025@linuxfoundation.org> References: <20191119051400.261610025@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Al Viro commit e72b9dd6a5f17d0fb51f16f8685f3004361e83d0 upstream. lower_dentry can't go from positive to negative (we have it pinned), but it *can* go from negative to positive. So fetching ->d_inode into a local variable, doing a blocking allocation, checking that now ->d_inode is non-NULL and feeding the value we'd fetched earlier to a function that won't accept NULL is not a good idea. Cc: stable@vger.kernel.org Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/ecryptfs/inode.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/fs/ecryptfs/inode.c +++ b/fs/ecryptfs/inode.c @@ -325,7 +325,7 @@ static int ecryptfs_i_size_read(struct d static struct dentry *ecryptfs_lookup_interpose(struct dentry *dentry, struct dentry *lower_dentry) { - struct inode *inode, *lower_inode = d_inode(lower_dentry); + struct inode *inode, *lower_inode; struct ecryptfs_dentry_info *dentry_info; struct vfsmount *lower_mnt; int rc = 0; @@ -345,7 +345,15 @@ static struct dentry *ecryptfs_lookup_in dentry_info->lower_path.mnt = lower_mnt; dentry_info->lower_path.dentry = lower_dentry; - if (d_really_is_negative(lower_dentry)) { + /* + * negative dentry can go positive under us here - its parent is not + * locked. That's OK and that could happen just as we return from + * ecryptfs_lookup() anyway. Just need to be careful and fetch + * ->d_inode only once - it's not stable here. + */ + lower_inode = READ_ONCE(lower_dentry->d_inode); + + if (!lower_inode) { /* We want to add because we couldn't find in lower */ d_add(dentry, NULL); return NULL;